Landscape and Building Design for Bushfire Areas

Landscape and Building Design for Bushfire Areas

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Landscape and Building Design for Bushfire Areas

Caird Ramsay & Lisle Rudolph

Text and illustrations © 2003 G. Caird Ramsay and Lisle Rudolph All rights reserved. Except under the conditions described in the Australian Copyright Act 1968 and subsequent amendments, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, duplicating or otherwise, without the prior permission of the copyright owner. Contact CSIRO PUBLISHING for all permission requests. National Library of Australia Cataloguing-in-Publication entry Ramsay, G. Caird. Landscape and building design for bushfire areas. Bibliography. Includes index. ISBN 0 643 06904 6. 1. Landscape design – Environmental aspects – Australia. 2. Buildings – Protection – Australia. 3. Dwellings – Fires and fire prevention – Australia. I. Rudolph, Lisle S. II. CSIRO. III. Title. 712.0994 Available from CSIRO PUBLISHING 150 Oxford Street (PO Box 1139) Collingwood VIC 3066 Australia Telephone: Local call: Fax: Email: Web site:

+61 3 9662 7666 1300 788 000 +61 3 9662 7555 [email protected] www.publish.csiro.au

Set in Lucida 9.25/13 Cover and text design by James Kelly Printed in Australia by BPA Print Group Disclaimer Because the information presented in this book is of a general nature, the authors and publisher do not accept any liability for its accuracy or completeness or its fitness for any particular purpose. It is the responsibility of users to seek expert advice where appropriate and to comply with all regulatory authorities at Federal, State, regional and local levels.

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Foreword This design manual is intended to help people to design buildings and the landscape settings immediately around them so that the buildings (and the people sheltering in them) will have a better chance of surviving in the event of a bushfire. It contains a theoretical explanation for the design recommendations and therefore can serve design professionals in the building and landscape industries, as well as students in these areas. Homeowners may also find this manual useful. Because design is an ongoing activity, this manual can be used not only for new developments but also to modify existing properties to make them safer. The manual has two main sections: • What happens in a bushfire? • Designing for bushfire areas The first section describes the environment in which bushfires occur, the bushfire attack and how buildings can be ignited and destroyed in a bushfire. The second section begins with a general methodology for designing and then presents different options for designing the various elements of landscapes and buildings in bushfire-prone areas. Landscapes and buildings are treated in separate chapters. Those who understand the few basic principles given in Chapters 2 and 3 (‘The bushfire’ and ‘Ignition and destruction of buildings’) can work out the best design solutions for themselves, or they can go directly to the two chapters of recommended Design Options in Section two. New options may also be developed in the future using the methodology in this manual.

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Acknowledgements This manual began when the authors set out to develop a companion book to their video tape, ‘Buildings and Bushfires’ produced by the University of Melbourne in 1988. Since that time there have been many developments in the field, particularly in the landscape aspects. The development of this manual was brought forward by the help of funding from Emergency Management Australia (EMA) as part of its ongoing program of promoting Disaster Prevention/Management Projects. This assistance from EMA is gratefully acknowledged. The authors also wish to thank the following people for their expertise and generous assistance: Professor Catherin Bull, Professor of Landscape Architecture, University of Melbourne Klaus Braun, Fire and Emergency Services Authority of Western Australia David Cant, Emergency Services Administrative Unit, South Australia Dr N.P. Cheney, CSIRO Forestry and Forest Products, Canberra Mark Chladil, Tasmania Fire Service Dr Noreen Krusel, Country Fire Authority, Victoria Mrs Janne Morrison, Faculty of Architecture, Building and Planning, University of Melbourne Peter Nassau, Building Control Commission, Victoria Mike Niven, Department of Natural Resources and Environment, Victoria Lisle Rudolph also wishes to acknowledge the help provided by the Faculty of Architecture, Building and Planning at the University of Melbourne, where he worked on the early development of this work when a Faculty member, and for the opportunity to work during special study leave at CSIRO Division of Building, Construction and Engineering, Highett, Melbourne. Caird Ramsay Lisle Rudolph Melbourne, May 2003

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Contents Section one: What happens in a bushfire? Chapter 1: Introduction Planning and building regulations — a cautionary note Bushfire hazard in Australia 2 Adapting to bushfire 3 Community responses to bushfire risk 4 Individual responses to bushfire risk 4 Appropriate form of information 5 A design approach 5 Common misconceptions 6

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Chapter 2: The bushfire Causes of bushfires 8 Mechanisms of spread 8 Influence of fuel 10 Ignition and burning of different types of fuel Influences other than fuel 12 Summary 12

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Chapter 3: Ignition and destruction of buildings Importance of ignition 13 Kindling 13 Ignition mechanisms 15 Attack period 18 Modes of attack 21 Buildings as refuges from bushfires

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Chapter 4: Evaluation of vegetation for use in landscaping General considerations 22 Attributes of plants which affect a bushfire attack Modes of attack 29 Performance characteristics 30 Use of the performance characteristics 31

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Section two: Designing for bushfire areas Chapter 5: Design – general Priorities for design 34 Design options 35 Landscape and building approaches Maintenance 37 Robustness 37

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Chapter 6: Landscape design The landscape approach 39 Attitudes to vegetation 41 Vegetation management 42 Robust landscape options 44 A methodology for landscape design

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Chapter 7: Landscape design options Planning requirements – a cautionary note Choosing a suitable lot 47 Landscape style 49 Design options 52 Trees and shrubs 53 Landforms 57 Ground cover and mulches 60 Screen planting 61 Open spaces 65 Fences and garden walls 66

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Chapter 8: Building design The building approach 67 Exterior refuges 68 Robust building options 68 A methodology for building design

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Chapter 9: Building design options Building regulation requirements — a cautionary note 72 Design options 72 Plan shape 75 Roof profile 76 Roof cladding 79 Roof gutters 83 Floors and underfloor spaces 85 Verandahs, decks, steps, landings, pergolas and trellis 87 Walls 90 Doors, windows and vents 92 Outbuildings and storage facilities 95 Services 97

Glossary 101 References and further reading 102 Index

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S e c t i o n

o n e

What happens in a bushfire? This section describes the environment in which bushfires occur and the problems facing people living in areas prone to bushfire. It explains how bushfires attack, how buildings ignite and the relevant attributes of vegetation.

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Chapter 1: Introduction Every bushfire season in Australia increases the urgency to design buildings and their landscape settings so that they are better adapted to their environments. This chapter touches on some of the responses of people to the risk of bushfire in bushfire-prone areas and lists some common misconceptions. The chapter also describes the design approach used in this manual.

Planning and building regulations — a cautionary note Before proceeding to develop any proposals, designers should first check all planning requirements that have to be met, covering factors such as zoning, siting of buildings and management of vegetation. A similar check should be made with regard to all building regulations. In all cases, these requirements take precedence over anything contained in this manual. Designers should also refer to the Australian Standard AS 3959 – 1999 and amendments, Construction of Buildings in Bushfire-prone Areas, which is the current edition at the time of writing this manual. This Standard is a primary reference standard for the Building Code of Australia (BCA) which applies throughout Australia, and there are variations to it at both State and local levels. However, this manual may provide information which facilitates the design of ‘alternative solutions’ under the BCA performance approach.

Bushfire hazard in Australia Australia, like most parts of the world, has its share of natural hazards, including earthquakes, cyclones, droughts, and bushfires. Large bushfires also occur in several other regions of the world including California, Southern France, Central Spain, Russia and China. Australian bushfires can 2

Introduction

be particularly large, severe and destructive. In Australia, the climate and the vegetation combine each year to produce fire-hazardous conditions across vast areas. When concentrations of flammable vegetation, high temperature, low humidity and very strong wind all occur together, they set the stage for a serious and destructive bushfire.

Adapting to bushfire Aboriginal Australians were well adapted to their environment, and they used fire to assist in hunting and food gathering. On the other hand the Europeans who first began to settle in Australia would not have encountered fires on such a scale before, and must have feared them. Uncertainty and fear remain with many people today. At the same time there are others who are gradually coming to accept bushfire as part of their country through increased understanding of what happens in bushfire. The most recent development has been to plan to prepare buildings and their surroundings so that, when a bushfire does come, it will be less destructive and people will be better able to survive. An essential requirement for this to happen is the knowledge about how buildings are ignited and destroyed in a bushfire. This knowledge has been slow in coming for several reasons. The limited amount of research on the ignition of buildings may be due, in part, to the infrequent occasions on which researchers have had the opportunity to study a sufficient number of buildings at any one time to provide statistical reliability, and to the difficulties inherent in this type of research. One of the first significant studies undertaken was in 1944 after a fire in Beaumaris, an outer suburb of Melbourne, but the findings were relatively inconclusive. A major step forward in the research came after the Ash Wednesday bushfires of 16 January 1983. On that day in Victoria and South Australia 76 people died, 2463 houses were destroyed and 360,000 hectares of land were burned. The cost of the damage has been estimated at $440 million, not to mention the human costs of trauma and disruption to people’s lives. In the Ash Wednesday fires, the very large number of buildings that were either destroyed, ignited but not destroyed, or not ignited at all, provided a statistically large sample. Some fairly reliable conclusions were able to be drawn about the ignition and destruction of buildings. These are elaborated in Chapter 3 in this manual, ‘Ignition and destruction of buildings’. 3

Introduction

Community responses to bushfire risk Communities respond to the risk of bushfire in various ways. Many rural communities are familiar with fires, have much at stake if burned out, and they prepare for them regularly. In other areas, particularly the expanding urban fringes, people are less likely to be aware of bushfires. Within each community there will be a range of personal responses as well. The following table shows the different ways in which communities and individuals can respond. It also shows the area of activities which this manual deals with.

Responses to the risk of bushfire

Reduce causes of bushfires

Education and awareness programs and law enforcement

Reduce the hazards

Land use planning by authorities including fire hazard mapping Annual hazard reduction by authorities Annual hazard reduction by individuals Low hazard site selection by individuals Landscape design (e.g. this manual)

Reduce loss potential

Forecasting fire danger days and periods and warning systems Provision and designation of refuges Community group co-operation Fire fighting Improved design of buildings through education (e.g. this manual) and regulations

Adjust to losses

Spread the losses through public appeals, Government assistance and charities Plan for losses through insurance Acceptance of the losses by individuals

Individual responses to bushfire risk It is difficult to know to what extent individuals are currently conscious of the risk of bushfire, and what they are doing, if anything, to prepare their properties for the possibility of a bushfire. Undoubtedly, a bushfire does increase the awareness of people for a few years afterwards but then, as vegetation grows back quickly and normality returns, awareness and preparedness decline. There are probably several reasons for this decline. One reason may be a healthy tendency not to dwell on the hazards and negatives of life. Nevertheless this does not reduce the need for reliable information to be available to those who do want to increase their preparedness and the 4

Introduction

peace of mind that goes with that. The successful efforts of some people will eventually spread and become conventional wisdom to others.

Appropriate form of information Another reason for lack of action may be the information available. Some people may be well aware of the hazards, but may be confused by the information or the form in which it is available. While there are a number of publications about buildings and bushfires, people may have difficulty in applying the information to their own individual situations. For example some advice offered describes all of the many measures that can be taken as things that ‘should’ be done. The reasons why they should be done are often not given, nor are alternative courses of action offered. The result may be a list of ‘do’s’ and ‘don’ts’ that is long, intimidating and in some cases too expensive and inappropriate for the individual situations.

A design approach The design approach taken in this manual first states the objectives that need to be achieved, and then offers a range of design options (solutions) to achieve them. People can then choose the options that fit in with the rest of their designs. Furthermore they can also decide to reject any advice knowingly on the basis that they are aware of the problem and the likely extent of the risks they are taking. For example, one objective in bushfire areas is to deal with the risk of buildings being ignited in the sub-floor space. The problem can be eliminated by the use of a concrete slab-on-ground floor. If a timber floor is desired for some reason, such as a steeply sloping site, then there are other design options, such as enclosing the sub-floor space with non-combustible materials and/or managing the vegetation nearby. A non-design approach might simply state, ‘use concrete slab-on-ground for floors’.

5

Introduction

Common misconceptions Another reason for lack of preparation for bushfires may be a number of misconceptions about buildings and bushfires. There seem to be several common misconceptions in circulation. Some of these could discourage people from doing anything to prepare, while others could lead them into doing the wrong thing (such as evacuating their house at the wrong time). Some of these misconceptions are listed below, together with their counterfacts.

Misconception 1 ‘Bushfires are usually so severe that there is nothing you can do, and it is not worth the trouble and expense of preparing for them.’

Counter-fact 1 While many buildings are destroyed by bushfires, many others survive similar conditions, not just by chance but because all buildings perform in bushfire according to known scientific principles. Buildings and their surroundings can be designed according to these principles to improve greatly the chances of survival.

Misconception 2 ‘The heat of bushfires is so intense that buildings made in the usual way could not survive. Only a brick or concrete bunker could survive and I don’t want to live in that!’ Objects such as melted glass in the burnt remains of a building are taken as evidence to support this view.

Counter-fact 2 There is no denying that bushfires generate large amounts of heat and very high temperatures. However, in some cases such as the ‘melted glass’ it is the heat of the building itself burning that melts the glass, not the heat of the bushfire. A building is usually a concentration of combustible fuel capable of sustaining an intense fire longer than the vegetation around it, except perhaps in some cases where the vegetation is a forest with a very heavy concentration of fuel.

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Introduction

Misconception 3 Many people understandably seem to have an intuitive belief, based on their limited experience with fire, that most things which catch fire are ignited by flame. This may lead to the belief that flames from the bushfire are the major threat.

Counter-fact 3 Research indicates that ignition of buildings is much more likely to be caused by wind-driven embers and other burning debris than by flames of the bushfire itself. These ignitions may be caused directly by embers and burning debris coming into contact with a combustible part of the building, or indirectly by embers and burning debris lodging in combustible litter or other debris and then igniting the building. Flame attack from the bushfire lasts only for the several minutes during the passage of the fire front at the building. The attack of wind-driven burning debris may go on for hours, particularly after the fire front has passed, and embers will continue to be blown from piles of long-burning material and ashes.

Misconception 4 ‘Buildings explode in bushfires.’

Counter-fact 4 There is no known scientific evidence to support the view that buildings suddenly explode due to the heat of the bushfire. The phenomenon reported as an explosion may be a ‘flashover’. Flashover occurs in an enclosed room when a stage is reached where combustible materials are heated sufficiently to produce flammable vapours. With additional air, such as may occur with the opening of a door or breaking of a window, the fire grows suddenly to give flames throughout the compartment. The fear that buildings may explode in a bushfire (except from known causes such as stored flammable liquid for example) could cause occupants to evacuate a building at the very time when conditions outside, from radiant heat especially, are such that they may be lethal, and it would be better for them to stay indoors longer. 7

Chapter 2: The bushfire This chapter briefly describes the mechanisms by which a bushfire spreads. It gives a very simple classification of the fuel types that feed a bushfire and explains how these fuel types influence the attack on a building.

Causes of bushfires There will always be bushfires in Australia because of the combination of the climate and the vegetation. Lightning is a frequent cause of bushfire. Sparks from farm machinery, traffic accidents and malicious or careless acts by people are all examples of possible bushfire starters. Education and laws can help to modify certain types of behaviour, but there are some events that can never be eliminated entirely.

Mechanisms of spread A bushfire can start from a very small flame in very fine fuel. There are three ways in which a small fire can spread and grow: • embers and burning debris carried by the wind, • heat radiation from the fire, and • direct flame contact.

Embers and burning debris The term ‘embers’ is used to describe small particles of burning material. These can be driven forward in large quantities by the wind and may also be carried upwards and forward long distances ahead of the fire front and remain alight throughout (see figure opposite). If the embers and other forms of debris are alight when they land among fine dry fuel such as grass and leaf litter, they can ignite it, especially if fanned by the wind. 8

The bushfire

Radiation Radiant heat is given out in all directions from a fire, drying and heating fuel around it to a temperature where it either bursts into flame or is ignited by flames (see figure below).

Direct flame contact Flames may contact adjacent material and ignite it, and the wind can extend their range (see figure below). Fire spreading by flying embers and burning debris

Fire spreading by heat radiation

Fire spreading by direct flame contact

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The bushfire

Influence of fuel Of the many factors that influence the spread of bushfire, fuel is of major importance. It consists mostly of vegetation, both growing and as debris on the ground. The nature of this fuel affects the speed and intensity of the fire, and also the size of the embers and wind-driven debris produced. The factors that make up the nature of the fuel include its chemical composition, its moisture content at the time, and the size, shape and distribution of the pieces of material. If the pieces are close together radiation is more able to assist the spread of fire, but if they are too close the supply of air will be restricted and this will slow the burning process.

Ignition and burning of different types of fuel For the purposes of this manual, fuel may be considered as fine, intermediate or dense.

Fine fuels Fire spreads quickly in fine dry fuels such as grass and leaf litter. A large surface area is exposed to the fire and, in loosely compacted fuel, a free flow of air will support burning. Fine fuel burns intensely for a short time, but its relatively small mass does not sustain burning for long.

Intermediate fuels Between the two extremes of fine fuel and dense fuel, there is a range of types for which ignitability, rate of burning, duration of burning and amount of heat produced all vary. This subject is dealt with more fully in Chapter 4, ‘Evaluation of vegetation for use in landscaping’.

Dense fuels In dense fuels, such as logs, ignition does not occur readily. The surface area in relation to volume is small and the supply of air is restricted because of the concentration of fuel in large masses. However, once alight, the amount of heat given out is high and the burning process will go on for a long time. For the purposes of this manual, the three grades of fuel, (fine, intermediate and dense) can be represented by three vegetation types: grassland, scrub and forest.

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The bushfire

The three vegetation types

Grassland

Scrub

Forest

Grassland Fires move faster in grass than in any other type of vegetation, and speeds up to 18 km per hour have been recorded. Grassfires are relatively shortlived and are of relatively lower intensity because the mass of fuel is small. Grass produces small embers which do not persist for long.

Scrub Scrub consists of bushes, small multi-stemmed trees and the like. The more litter there is on the ground to pre-heat the scrub above it, the more readily it will ignite, even if the leaves are green. Leaves and twigs will burn quickly and fiercely like grass. If the trunks ignite the fire will be sustained longer and be more intense. Embers from a scrub fire will be larger than those from a grass fire and burning debris may also be produced by a scrub fire.

Forests In forests, the tree trunks, logs and densely compacted litter sustain intense fire for a long time. For the leaf canopy of trees to ignite and spread fire requires sufficient burning litter and scrub under the trees to pre-heat the leaf canopy. Forest fires do not always crown, and the fire can be carried through surface and elevated fuels. Forest fires produce burning debris as well as embers, the burning debris consisting of pieces of burning bark and branches which can burn for a long time and are driven by the wind. 11

The bushfire

Influences other than fuel Besides fuel there are other influences on the spread of bushfire, including humidity, wind and ground slope.

Humidity The humidity affects the moisture content of fuel and therefore its ease of ignition and rate of burning. If fuel is damp, some of the heat incident on it is expended on evaporating the water first before ignition occurs.

Wind Major bushfires in Australia are associated with very strong winds, often of gale force. The wind pushes the flames forward, increases the supply of air to the fire, carries embers and burning debris forward and strongly influences the speed and direction of the fire. The air movement in and around a bushfire is significantly added to by the convection currents of hot air rising from the fire and relatively cooler air moving in to replace it.

Slope The slope of the ground affects the speed of a bushfire, with fires burning faster uphill than down, the speed increasing with increasing slope.

Summary Bushfires originate in fine fuel. They spread by way of embers and burning debris, radiation and flame, and their speed and intensity are determined largely by the nature of the fuel present and the weather conditions. Bushfires can be very large and intense, but they are not supernatural events. They do not move with the speed of express trains as some people believe, and their behaviour is in accordance with known scientific principles. Their effect on buildings is thus predictable and can be planned for.

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Chapter 3: Ignition and destruction of buildings This chapter describes the different ways in which buildings can be ignited and damaged or destroyed in a bushfire. It explains how flammable litter and debris build up around, on, under and inside buildings. It then describes and illustrates the sequence of events from the approach of a bushfire until several hours after it has passed.

Importance of ignition Research has shown that, during bushfires, most building fires start with small ignitions. These ignitions progress slowly at first, accelerate and progressively involve the whole building. If the small ignitions can be prevented in the first place the larger fire will not follow.

Kindling The ignition of a building is made easier by the build-up of leaf litter and other debris both before and during a fire. Embers and burning debris blown into this fine fuel can kindle a flame against heavier combustible material on a building and ignite it. The heavier material may already have been heated by radiation. If the heavier material is wood it will be even more vulnerable if it is rough sawn, splintered, split, weathered or decayed. Dry leaves and twigs, especially common with Australian native vegetation, are a prolific source of ‘kindling’ for igniting buildings. Leaf drop is heaviest during the hot dry season when plants become stressed due to lack of water. In addition to being highly flammable, the leaves and twigs remain stiff and do not decompose or crumble easily and consequently do not compact readily. Dry leaves and twigs, blown by the wind, pile up outside buildings, against vertical surfaces and on horizontal elements, under buildings and inside buildings, through gaps in the roof and wall claddings. 13

Ignition and destruction of buildings

There are many places around, on, under and inside buildings where leaf litter and debris accumulates both before and during a bushfire.

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Kindling accumulation points: 1 In re-entrant corners 2 Against vertical surfaces 3 On horizontal, or near-horizontal, surfaces 4 Under buildings 5 Inside buildings 6 Around, on, under and inside outbuildings

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1 In re-entrant corners Re-entrant corners in the plan of a building accumulate debris where they abut horizontal surfaces, such as the ground, decks, door thresholds and window sills. 2 Against vertical surfaces Vertical surfaces, such as walls, doors, window frames, posts, poles, plinth boards and trellis, accumulate debris where they abut horizontal, or near-horizontal, surfaces, such as the ground, roofs, verandahs, decks, door thresholds and window sills. 3 On horizontal, or near-horizontal, surfaces Horizontal, or near-horizontal surfaces, such as roofs, verandahs, gutters, decks, steps, landings, pergolas, door thresholds and window sills, accumulate debris, especially where they abut vertical surfaces, such as walls, doors, window frames, posts and poles. 4 Under buildings The ground underneath buildings accumulates debris where it abuts vertical surfaces, such as stumps, posts, poles and plinth boards. 5 Inside buildings The roof and living spaces accumulate debris blown by the wind through openings, such as gaps in and around roof cladding and gutters, gaps in walls, gaps under doors and open windows. 6 Around, on, under and inside outbuildings The areas where debris can accumulate are the same as those described above for the main buildings.

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Ignition and destruction of buildings

Ignition mechanisms As described in Chapter 2, a bushfire can ignite fuel and spread in three ways. A bushfire can ignite a building in the same three ways: • embers and burning debris carried by the wind, • heat radiation from the fire, and • direct flame contact.

Ignition of buildings by burning embers and debris carried by the wind

Ignition of buildings by heat radiation from the fire

Ignition of buildings by direct flame contact

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Ignition and destruction of buildings

Ember and burning debris ignition Embers and burning debris, driven by wind, are produced in large quantities by bushfires. If they come in contact with a combustible part of a building or its contents, they can ignite the building. The ignition is facilitated if the ‘kindling’ discussed above has accumulated at the points of ignition. There are a number of places around, on, under and inside buildings where ember and burning debris ignitions can occur. Most of these places are the same as those, described above, where kindling accumulates.

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Ember ignition points: 1 Re-entrant corners 2 Vertical surfaces 3 Horizontal surfaces 4 Under buildings 5 Inside buildings 6 Around, on, under and inside outbuildings

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1 Re-entrant corners Ignitions can occur if the corners are lined with timber or if the corners abut horizontal timber surfaces. Stacking combustibles, such as firewood and building materials in the corners increases the likelihood of ignition. 2 Vertical surfaces Ignitions can occur if the surfaces are timber or abut horizontal timber surfaces. Stacking combustibles against the vertical surfaces increases the likelihood of ignition. 3 Horizontal or near horizontal surfaces Ignitions can occur if the surfaces are timber or abut vertical timber surfaces. In the case of roofs, verandahs and gutters which are generally made from non-combustible materials, accumulated embers and burning debris can make their way into the roof space and ignite combustible materials there (see below). Leaving combustibles, such as outdoor furniture and doormats, on horizontal surfaces, such as decks and landings, increases the likelihood of ignition.

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Ignition and destruction of buildings

4 Under buildings Ignitions can occur if the floor or its supporting structure is timber. Storage of combustibles under the building increases the likelihood of ignition. 5 Inside buildings Embers and burning debris can be blown inside the roof and living spaces of buildings in the same way as described for ‘kindling’ above. Under bushfire conditions, the breakage of windows by heat and wind-blown objects greatly increases the likelihood of this happening. In addition, the very strong winds can loosen roof and wall cladding materials and again open up the building to ignition. Once inside, the embers and burning debris can ignite the timbers in the roof space and the contents of rooms. 6 Around, on, under and inside outbuildings The places where embers and burning debris can ignite outbuildings are the same as those described above for the main buildings. Outbuildings are often not built or maintained to the same standard as the main buildings and are therefore more vulnerable. In fact, burning outbuildings can provide a source of ignition for main buildings.

Heat radiation ignition Radiation can ignite timber directly on the outside of a building, but this only happens when a large quantity of fuel, such as an outbuilding, a heavily overgrown garden, or forest-like vegetation burns close to the building. Radiation plays a significant role however in heating up fuel so that ignition by embers or flame is easier. There are other serious consequences of heat radiation. Windows can be cracked or broken allowing embers to enter, and plastics such as wall cladding can be distorted badly or melted to expose combustible framing. Most serious is the danger of radiation to people, and this will be discussed below under ‘attack period’.

Direct flame contact ignition Ignition of a building by direct flame contact can occur if hazardous vegetation or other fuel such as an outbuilding, garden refuse, or a wood heap burns against or very close to it. A building set in a forest or in heavy scrub, or in an overgrown garden is a good candidate for ignition by flame. 17

Ignition and destruction of buildings

Attack period The attack of a bushfire on a building goes through three stages: • pre fire front, • impact of the fire front, and • post fire front.

Pre fire front The attack begins when embers and and burning debris blown ahead of the fire reach the building and its surroundings (see figure below). As the fire comes closer, the attack by embers and burning debris increases. Generally this attack can last for up to half an hour before the fire front itself arrives. Since there is no radiation from the fire front around the building during this period, it is relatively safe for people to be outside, putting out any ignitions in the vegetation, on the exterior of the building or under the building. The inside of the building, including roof spaces, should also be monitored for embers and burning debris. Timescale of attack: pre fire front

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Ignition and destruction of buildings

Impact of the fire front The second stage starts when the fire front arrives (see figure below). Ember and burning debris attack, heat radiation, flames and smoke are at their maximum, but this may only last for 5 to 10 minutes depending on the fuel type while the fire front passes. In a grass fire this period may be only 1–2 minutes. During this time the noise of the wind and the fire can be terrifying, and conditions outside are usually lethal due to the radiant heat. Everyone should shelter inside, watching for ignitions and putting them out as they occur. Timescale of attack: impact of the fire front

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Ignition and destruction of buildings

Post fire front After the fire front has passed (see figure below), embers and burning debris continue to be blown from burning tree trunks, outbuildings, fence posts and wood heaps. This final stage may last for several hours, and the risk of ignition remains high for a long time. When the level of radiation outside has fallen sufficiently, properly clothed people can go outside and put out fires on and around the building. A check should be kept inside the building, and in concealed spaces in the roof and under the floor, and a watch kept for a change in wind direction. If people who have evacuated before the bushfire return during this period, they can also carry out these fire-fighting activities. Many buildings are ignited and destroyed during this final stage, and it is often the most important period for building survival. Timescale of attack: post fire front

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Comparative frequency of ignition types Research indicates that buildings are more frequently ignited by embers and burning debris than by radiation and flame contact. There are many parts of a building vulnerable to ignition by embers and burning debris. The probability of ignition by this mode of attack is increased because the risk is present for several hours: before, during and after the impact of the fire front. In contrast, ignition by radiation and flame contact only occurs during the few minutes of the impact of the fire front.

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Ignition and destruction of buildings

Effects of wind The ignition and destruction of buildings by embers and burning debris are helped by strong winds. The wind drives litter, embers and burning debris against buildings, underneath and inside them. The wind carries debris such as branches and sheets of roofing iron which can break windows and skylights, allowing embers and burning debris to enter. It can also loosen roof materials, or in extreme cases lift off roofing.

Modes of attack As described above, there are three ways by which a bushfire can ignite a building. When wind damage to a building — allowing the entry of embers and burning debris — is added, there are four modes of attack. These are: • embers and burning debris carried by the wind, • heat radiation from the fire, • direct flame contact, and • wind damage to the building allowing ember and burning debris entry.

Buildings as refuges from bushfires An understanding of how buildings are ignited and destroyed is the basis for designing or modifying buildings and their immediate landscape settings to increase the chances of survival of the buildings. The buildings can then be better refuges for people sheltering inside from the bushfires. A better knowledge of the stages which a bushfire attack on a building passes through would help to inform decisions about what people should do, when they should do it, and why. There are also many other important factors that influence these decisions, including peoples’ behaviour in these situations, but these are outside the scope of this manual.

21

Chapter 4: Evaluation of vegetation for use in landscaping When designing the landscape near buildings, decisions have to be made about which species of plants are to be retained, removed, or planted anew. These decisions are influenced by the many different attributes each species possesses. This chapter deals in some detail with these considerations.

General considerations Vegetation provides most of the fuel for bushfires. All plants, no matter how green or succulent they are, will eventually burn if the fire is intense enough. Vegetation can be in the form of growing plants, dead plants or as litter on the ground. In choosing plants for the landscape their performance in bushfires is of course not the only characteristic to be taken into account. Other characteristics that should be considered to make a balanced choice include: • functionality (such as provision of shade and protection from wind, screening of undesirable views and visual privacy), • suitability for the area, • drought resistance, • growth rate, • ability to support wildlife, and • appearance and character.

Dual role of vegetation Vegetation can have a dual role in bushfires. As well as providing fuel for the fire, many plants also possess properties which help to protect 22

Evaluation of vegetation for use in landscaping

buildings. If the plants themselves can be prevented from igniting, they can improve the defence of buildings by: • filtering out wind-driven burning debris and embers, • deflecting wind-driven debris and embers up and over, or around, a building, • acting as a barrier against radiation and flame, and • reducing wind forces which might damage the building.

Need for a systematic approach to the performance of vegetation There are at present a number of publications which provide advice about the use of vegetation to reduce bushfire hazard near buildings. They often refer to ‘bushfire-resistant’ plants and describe some of the characteristics that are considered to make them ‘bushfire-resistant’. A list of such plants is often provided, and many of these are imported species. Where the term ‘bushfire-resistant’ is used it is probably intended to mean that the plant is not very flammable. In this manual the term ‘flammability’ is preferred when describing the ability of a plant to ignite and burn in a fire. When referring to the ability of a plant to survive fire and live afterwards, the term ‘fire tolerance’, or its reciprocal ‘fire sensitivity’ is preferred. However this concept is not within the scope of this manual. Flammability is not the only characteristic of a plant which affects its performance in a bushfire. Many attributes of plants affect bushfire attack on buildings and, as a step towards a systematic approach, fourteen attributes of plants have been identified.

Attributes of plants which affect a bushfire attack There are fourteen attributes of plants which can affect the bushfire attack on a building (see table on next page). These can be divided into two groups — those that belong to the growing plant and those that belong to the ground litter produced by the plant. Within the growing plant group there are two sub-groups — attributes that describe the chemical composition of the leaves and those that describe the architecture of the plant. Architecture refers to the size and shape of the overall form, the parts such as the branches and leaves and the arrangement of these parts in relation to each other. 23

Evaluation of vegetation for use in landscaping

Growing plant attributes: Chemical composition of leaves

Growing plant attributes: Architecture

Ground fuel attributes

Moisture content

Leaf fineness

Volatile oil content

Density of foliage

Quantity of ground fuel available in fire season

Mineral content

Continuity of plant form

Fineness of ground fuel

Height of lowest foliage above ground

Compacting ability of ground fuel

Size of pla nt in terms of its volume and spread

Mineral content of ground fuel

Dead foliage on plant Bark texture

The fourteen plant attributes

Moisture content of leaves The presence of water in fuel retards ignition and the rate of combustion. In addition, the presence of water vapour in flames substantially reduces the radiant heat output. Since radiant heat is important to the spread of fire through heating fuel ahead of the flame, this reduction of radiant heat, combined with the reduced rate of combustion, explains why moisture content is so important to fire behaviour. Most Australian trees and shrubs have a low moisture content (80–150% of their oven-dried weight) compared with a high moisture content (250–400%) in exotic deciduous trees. Introduced evergreen hardwoods and conifers fall between these two extremes.

Volatile oil content of leaves The heat of combustion of volatile oils is high but their concentration in forest fuels is so small that they can make only a slight contribution to the total heat output. However, the effect of the oils is most apparent in the early stages of burning when the rate of combustion is slow, particularly in the presence of water. The oils are readily volatile and with their high calorific output, they promote combustion in the early stages of a fire. Their presence encourages burning even when the leaves are green.

Mineral content of leaves The higher the level of total minerals present in leaves, the lower the flammability. In tests to compare the effect of mineral content on flammability of a varied selection of species, eucalyptus leaves were found to be the most flammable, even after the volatile oils were removed.

24

Evaluation of vegetation for use in landscaping

Leaf fineness In general terms, the finer the fuel particles the more rapid the rate of spread of fire, provided there is sufficient continuity of fuel to sustain combustion. The ratio of area-to-volume of leaves is one of the Broad Narrow main factors affecting ease of ignition and intensity of burning. A narrow leaf has a greater areato-volume ratio than a broad leaf and will therefore be more easily ignited and burn more intensely. This may be attributed to an ‘edge-factor’, the narrow leaf being more readily enveloped by flames and thus burning more rapidly (as shredded paper does compared to flat sheets).

Density of foliage Density is an indication of the amount of foliage material in a given volume of space within each branch or homogeneous concentration of foliage. Fuel distribution affects the means of heat transfer, Closely spaced Sparse radiation being more important than convection horizontally and less important than convection vertically. Combustion is most efficient when fuel is scattered enough to let ample supplies of oxygen to reach the flame zone, but dense enough for efficient heat transfer by both means. Dense foliage will filter out windblown debris and embers, block radiation and flame, and reduce or deflect wind forces better than less dense foliage. However, wind breaks require some permeability to eliminate the undesirable negative pressure on the lee-side of wind barriers.

25

Evaluation of vegetation for use in landscaping

Continuity of plant form A broken form of plant is one which has large spaces between separate branches or concentrations of foliage. The greater the separation, the less likely is the spread of fire by radiation and flame. A broken, open Connected form of plant will be a poor barrier.

Broken

Height of lowest foliage above ground The nearer to the ground that the foliage of trees and shrubs is, the easier it is for the transfer of heat and flame from fire burning on the ground up into the foliage above. Pruning lower branches High Low can modify this attribute, but this may reduce the ability of the plant to act as a wind barrier. A height of two metres above the ground has been suggested as a suitable height for pruning but this would depend on the situation.

Size of plant Volume and spread have different effects. The greater the volume of a plant, the larger the amount of embers, radiation and flame it can produce when it is burning. The greater the spread of a plant, the better it Wide Narrow performs as a barrier. Generally a wide-spreading tree is a better barrier than a tall narrow tree, even if they have similar volumes. 26

Evaluation of vegetation for use in landscaping

Dead foliage on plant Dead leaves and twigs still attached or suspended in a plant increase flammability. As trees grow, the canopy closes and lower inside branches become suppressed and die. Many deciduous trees and the Light eucalypts and other natives Heavy shed the dead lower limbs naturally. This is known as ‘self-pruning’. Conifers, however, are either not commonly self-pruning or do so only over a long period.

Bark texture Bark which is loose, flaky, stringy, papery or ribbonlike will provide a path for fire to spread up into the foliage. Bark texture can be as important as the continuity of under-storey shrubs under trees in the propagation of crown fires. Loose Tight Loose bark will also contribute to flame and radiation, and burning debris can originate from bark as it does from leaves and twigs.

Quantity of ground fuel available in fire season In most forest or grassland fuel types, the rate of spread of ground fire increases in direct proportion to the quantity of fine fuel available. Almost all fuel in grasslands may be Heavy described as fine but in

Light

27

Evaluation of vegetation for use in landscaping

forests fine fuel means dead fallen material such as leaves, bark, twigs and branches up to 6 mm in diameter. Only fuel which is present during a fire season need be considered. Most of the fuel that has fallen from deciduous trees in the autumn is not available as flammable fuel in the fire season following, due to compaction, decomposition and dispersal. Many Australian native species, on the other hand, drop fuel throughout the year, and the process is accelerated in the summer and under heat and drought stress. However, only a percentage of the total fuel on the ground will burn in the passage of the fire front, and this is termed ‘available’ fuel. The percentage available is influenced by the fineness and compaction of the particles, and in some cases a stage may be reached where compaction compensates for the addition of further fuel. The quantity of ground fuel is expressed in tonnes per hectare, and grass fuel is expressed in terms of its height, which can be related back to weight if necessary. Observers soon become accustomed to estimating fuel quantities from general appearance.

Fineness of ground fuel The finer the fuel the greater is the rate of spread of the fire. Radiated or convected heat cannot penetrate a fuel surface beyond a fraction of a millimetre, and therefore has a much greater effect in pre-heating grass and Fine leaves than bulkier material.

Coarse

Ignition is almost instantaneous throughout a piece of dry grass, but dry wood will light up only along its surface. Coarse material is not readily ignited unless fine fuels are also present and, when ignited, it adds little to the initial phase of combustion. Where the fuel is of varying fineness, the finer fuel is consumed during the passage of the fire front and the coarser fuels continue to burn later.

28

Evaluation of vegetation for use in landscaping

Compacting ability of ground fuel The parameters of fuel compactability appear to be particle size, stiffness and physical and chemical decomposition. Stiffness applies not only to leaves, but also to twigs and Packed closely Packed loosely branches in the litter. Hardness or stiffness is a quality common to much native Australian vegetation. Sclerophyll forests are composed mostly of hard-leaved species (from the Greek, skleros = hard, phyllon = leaf). The placement of individual pieces of fuel in relation to one another influences heat transfer and thus the rate of spread of fire. It is possible for fuels to be so compacted that oxygen is not readily available. The very slow burning of peat beds is an example of this.

Mineral content of ground fuel As already stated, for the mineral content of leaves on growing plants, the greater the mineral content the lower the flammability of leaves in ground litter. Once the leaves become ground fuel, the moisture and volatile oils dry out sufficiently to not be relevant.

Modes of attack As described on page 21, there are four modes of attack against a building. These modes are: • embers and burning debris carried by the wind, • heat radiation from the fire, • direct flame contact, and • wind damage to the building allowing ember and burning debris entry. Each species of plant will, because of its combination of attributes, influence the operation of these four modes and thus promote and/or reduce bushfire attack on a building. For example, a tree that has loose fibrous bark on its trunk will provide fuel more readily for ember and

29

Evaluation of vegetation for use in landscaping

burning debris attack than a tree with smooth tight bark. A tree with dense foliage will, other things being equal, be a better barrier against wind than another with more sparse foliage. Exactly how each of the fourteen attributes affect the attack through the four modes is difficult to establish at present. For example, the effect of moisture content of leaves on the production of embers is complex and would require much research.

Performance characteristics With our present state of knowledge, we can take only a simple approach to compare the effects of different plants on bushfire attack on buildings. We can consider how the degree to which any one attribute (for example bark texture) would tend to affect the performance of that plant in a bushfire, by either increasing or decreasing the attack on a building. The performance of a species can be described in terms of three characteristics: • flammability, • provision of ground fuel, and • barrier-forming ability.

Flammablity Flammability is a composite of ease of ignition, rate of burning and total heat output. The more flammable a plant is, the more it will promote bushfire attack. Flammability of a plant will not be taken here to include the nature of the ground fuel as that is considered separately.

Provision of ground fuel The greater the quantity of ground fuel persisting into the fire season, and the more flammable that ground fuel is, the more the plant dropping that fuel promotes bushfire attack. The leaves of many deciduous trees fall in the autumn, but they are decomposed and/or dispersed in the cooler months that follow. Most do not persist into the next fire season. Many Australian native plants, however, are evergreen, and heavy leaf drop occurs in the hotter dry period when the plants may be stressed due to lack of water. These leaves, along with dropping twigs and branches, are ready fuel for bushfires. 30

Evaluation of vegetation for use in landscaping

Barrier-forming ability The plants which form the best barrier against bushfires are those which can best filter out wind-driven debris and embers, reduce wind forces, and deflect wind and wind-driven debris up and over, or around a building. Attributes such as ‘large size (spread) of a plant’ and ‘dense foliage’ contribute towards barrier-forming ability, other things being equal. The effectiveness of a barrier of plants depends on they themselves not igniting and becoming part of the attack. Low flammability does delay and slow down burning and methods for delaying or preventing ignition will be described later under ‘vegetation management’ (see page 42). The effectiveness of a barrier is also influenced by its location and this is also dealt with later (see page 61).

Use of the performance characteristics The combined effect of the fourteen attributes on the performance characteristics is shown in the table on the next page. The effect is shown as a tendency to either increase or decrease the performance characteristic. For example, an increase in the density of foliage would tend to increase its barrier-forming ability, all other attributes being kept constant. Similarly, increasing fineness of leaves would tend to increase flammability. The table should not be used to add up the scores for any particular species to get an overall picture of the usefulness or otherwise of that species for landscaping near buildings. That cannot be done because both the attributes and the performance characteristics have different weightings. What the table does is enable us to identify the significant attributes (and combinations of attributes) of particular species and begin to understand their effect on the performance of that plant in a bushfire attack on a building. The table can be used as a checklist to identify problems and opportunities for a species. Anyone with enough experience, or access to knowledge about the nature and habits of individual species could use this approach. When one or more attributes of a species are known to be very serious, it is possible to ‘red-flag’ it for particular applications. This approach could be used to indicate whether a species is suitable or unsuitable for a given use.

31

Evaluation of vegetation for use in landscaping

Effect of attributes of plants on their performance characteristics

Performance characteristic Plant attribute

Degree of attribute

Flammability

Provision of ground fuel

Barrier-forming ability

Moisture content of leaves

high low

decrease increase

*

negligible

Volatile oil content of leaves

high low

increase decrease

*

negligible

Mineral content of leaves

high low

decrease increase

*

negligible

broad narrow

decrease increase

*

increase decrease

closely spaced sparse

increase decrease

*

increase decrease

Continuity of plant form

connected broken

increase decrease

*

increase decrease

Height of lowest foliage above ground

high low

decrease increase

*

decrease increase

Size of plant (volume)

large small

increase decrease

*

increase decrease

Size of plant (spread)

wide narrow

increase decrease

*

increase decrease

Dead foliage on plant

heavy light

increase decrease

*

negligible

Bark texture

loose tight

increase decrease

*

negligible

Quantity of ground fuel available in fire season

heavy light

increase decrease

increase decrease

negligible

Fineness of ground fuel

fine coarse

increase decrease

increase decrease

negligible

Compactability of ground fuel

packed closely packed loosely

decrease increase

decrease increase

negligible

Mineral content of ground fuel

high low

decrease increase

decrease increase

negligible

Leaf fineness Density of foliage

* Effect considered elsewhere in the table

32

S e c t i o n

t w o

Designing for bushfire areas This section describes a method for designing landscapes and buildings to overcome the problems of living in a bushfire area. It presents a range of options to assist in the design of the most important elements of landscapes and buildings.

33

Chapter 5: Design – general This chapter explains the general method for designing landscapes and buildings. The chapters that follow give specific guidelines for the landscape and for buildings.

Priorities for design It is unlikely that anyone would start designing their property with bushfire survival as their first priority because surviving a bushfire is not the main reason why people build. Hazards are problems that people would rather not have to think about and removing them does not give any positive enjoyment other than perhaps peace of mind. Nevertheless, the penalties for ignoring the risk of bushfire in hazardous areas can be severe. In the final analysis, design for bushfire can never be treated in isolation from all other requirements. Buildings and their surrounding landscaping should satisfy many requirements including human comfort and satisfaction, social, economic and environmental criteria, to mention just a few. Undue emphasis on the bushfire aspects would distract attention away from other fundamental requirements. Successful design for bushfire will only be achieved if it is seen as part of the wider context. The aim of this manual is to help people to include design for bushfire along with all of their objectives rather than as something added on afterwards. The key to integration of any objective is to include it early in the design process. If this is not done, it may be disruptive and expensive later when all of the other objectives have been dealt with. If bushfire objectives are acknowledged early in the process the design of buildings for bushfire need not necessarily compromise other objectives or lead to expensive or unconventional buildings. Design for bushfire survival applies not only to new buildings, but includes the modification of buildings and their surroundings over the whole of their lifetime. Therefore designing for bushfire is done by all those involved in that ongoing process, not just the design professionals. 34

Design – general

Design options In all designing, there is hardly ever a situation in which there is not more than one way of achieving an objective or solving a problem. The process of designing is not just a sequence of irreversible decisions taken one after another. A designer usually goes back and forth, trading off different options until a suitable solution is achieved. The approach taken in this manual is to state objectives first and then provide design options for meeting them. These options are based on design principles which have been derived from a consideration of how to combat each of the modes of attack which have been described in Chapter 3, ‘Ignition and destruction of buildings’. This approach offers designers the flexibility they need to meet their individual situations and is better than giving them a straight list of ‘do’s’ and ‘don’ts’. If designers understand what each objective is, they can choose the option or combination of options that suits them best.

Ready made bushfire house designs Both single-concept and ready-made bushfire house designs cannot be generally applied. In the case of single-concept solutions, such as building underground or relying on roof-top sprinklers, weak links will remain and a combination of design options is needed. Off-the-rack bushfire house designs are not readily adaptable to different lots and may include excessive or expensive features that are not appropriate for a given situation. Model display bushfire houses have contained such features in the past and may actually discourage people from designing for bushfire because they are restrictive. Furthermore the focussing of attention on the building as the means of improving the chances of survival will deflect thought away from what can also be achieved by the use of siting and landscaping. In fact, exploiting the assets of the landscape to provide some degree of protection and also modifying some undesirable aspects of it offers many opportunities to reduce destruction of buildings in a very cost-effective manner.

Conflicting objectives When bushfire design objectives conflict with other objectives, it is usually possible to trade off options between them. For example, someone may have a desire to have very large windows to capture a view and to allow sunshine to penetrate. These windows could be a serious weakness in a

35

Design – general

bushfire because they could be cracked by heat radiation or broken by wind-blown objects thus allowing embers to enter. There are various options, some of which may be used together, to resolve the conflict. For example, the designer could: • use special glass resistant to breaking (e.g. toughened glass), • reduce the size of panes of glass to increase strength, • use metal shutters externally (e.g. sliding, hinged or rolling vertically), • avoid locating combustible structures (e.g. pergolas) close to the windows, • avoid locating highly flammable vegetation close to the windows, and • protect the windows externally with plants that are suitable for forming a barrier against wind, embers, burning debris and radiation.

Landscape and building approaches The first four options listed in the example given for the protection of large windows involve the building itself, whereas the remainder require modification of the landscape. All of the design options that can be taken to improve the chances of survival of a building in a bushfire can be classified under two main approaches: • the landscape approach, and • the building approach. The landscape approach consists of choosing a suitable lot and landscaping the surroundings of the building to reduce the attack of a bushfire and the wind on the building. The building approach consists of designing the building so that it does not ignite readily when subjected to the attack of a bushfire and the wind. Either the landscape or the building approach used alone could conceivably provide a safe situation but only if taken to extreme. The well-watered exotic garden is an extreme example of the landscape approach and a concrete bunker would be an extreme example of the building approach. At one end of the scale, a person who wishes to live in an area which already has heavy flammable vegetation and who also places a high value on keeping the landscape virtually intact would have to rely on the building for survival (building approach). 36

Design – general

At the other end of the scale another person might have a building in which the design of the building itself cannot be compromised to accommodate bushfire objectives. Examples of this could be a historic building which must be preserved intact, or a new building which is required for some reason to have fully glazed walls. In both of these cases, the owners may have to rely largely on the design of the landscape (landscape approach). In nearly all cases, people would have the opportunity to choose a combination of both landscape and building approaches and to select a combination that suits them.

Maintenance Both the landscape and the building approaches require ongoing maintenance to remain effective. However, the landscape approach can require more attention, especially when it is being relied on. The need for maintenance of the building is often more evident, especially when the day-to-day use of the building is affected. For example, loose roofing, draughty gaps and decaying timber soon demand attention. On the other hand a garden may become overgrown quite quickly and present an increasing bushfire hazard. In particular, the original landscape design intentions may be forgotten through the passage of time or changing ownership. There is a way to solve this problem, at least partially, by using the concept of robustness in the choice of design options.

Robustness The best way to counter the tendency to lose the original intentions of a design is to choose design options that have the inherent quality of robustness. This applies to both landscape and building options. Robust design options are preferable to those that require ongoing effort and resources. Robust options are those which are likely to remain in place and operate effectively for a long time with little or no intervention by people. Examples of this are large cleared areas which have a long-term designated purpose such as parking areas or tennis courts. Some elements of a building are inherently more vulnerable to ignition or damage in a bushfire than others. For example, an internal roof gutter

37

Design – general

towards which the roof slopes inwards, (rather than outwards towards the external walls) can collect litter and burning debris, be out of sight and very difficult to clear, especially during a bushfire attack. To try to alleviate the problem, for example by enlarging the gutter, or making it more accessible for clearing, will not be very effective and is not a robust option. A better approach would be to eliminate the problem as early as possible in the design stage by using a roof design without internal gutters — a robust option. Robust options for the landscape and for the buildings are described fully in Chapters 6 and 8, ‘Landscape design’ and ‘Building design’.

38

Chapter 6: Landscape design This chapter explains the method developed in this manual for designing landscapes around buildings. The practical working details or landscape design options are given in the next chapter: ‘Landscape design options’.

The landscape approach In areas which are prone to bushfire, the design and management of the landscape in the immediate vicinity of buildings have great potential to improve the chances of survival of people and buildings. In most developments, the design of the building is treated first and the landscape comes later. In areas prone to bushfire it is better to start with the landscape, at least for some major issues. By starting with the landscape, there are greater opportunities to reduce bushfire hazard through siting of the building and by ‘vegetation management’. For a full description of the term ‘vegetation management’ see page 42. If the building has been located on site and constructed before consideration of the landscape, those opportunities may be lost through poor siting, loss of protective vegetation, or having insufficient space in the right areas for protective landscape works. When the landscape approach has been used effectively there is less need for the use of the building approach. There seems to be an increasing desire for people to live in closer contact with natural landscape for the second home and also for permanent living. For many of these people substantial modification of the native vegetation is not seen as acceptable. Many local councils have restrictions on the removal of native vegetation. However after several bushfires in recent years there have been knee-jerk reactions against the extensive retention of native vegetation in some areas. In both cases, there is a need to know more about the truth of the situation, and to be able to use the landscape approach in an intelligent fashion.

39

Landscape design

Lot size The landscape which affects a building may extend well beyond the lot boundaries. If one is dealing with a farm, the owner has many opportunities to use a range of design options. If the lot is small, such as an urban-sized lot, two problems may arise: • the opportunities to modify the potential for bushfire attack within the boundaries are limited by lack of space, and • the owner has no direct control over neighbouring land which may be a fire hazard. If neighbouring land is privately owned, co-operative communal action is needed. If the neighbouring land is public land such as a roadside or park, an approach to the controlling authorities is needed. A co-operative approach between a community and the local government or government department responsible for the management of the public land can mitigate bushfire hazard. In some areas the management of bushfire fuels may be controlled through hazard reduction notices.

Cluster principle Proper sub-division planning will assist in providing protection against bushfire. As an example, the principle of cluster sub-division could be applied in suitable areas.

Cluster-style sub-division

minor access road cluster courts

major access road 40

Landscape design

People who wish to build and live close to the bush in bushfire areas without necessarily being right in the bush may develop village-type or cluster land sub-divisions. In such sub-divisions, individual dwellings would be clustered together and the land which is close around them would be substantially cleared of hazardous vegetation. Buildings would still be within reasonable walking distance of the bush, but far enough from it to mitigate radiant heat and direct-flame contact ignition of buildings and to reduce the attack of wind-driven embers and burning debris. Large contiguous areas of vegetation could thus be kept relatively intact as a habitat for wildlife. When bushfire does come, the bush will burn but the cluster of buildings will have a very good chance of survival. This scenario would not be possible with the same land divided into suburban-sized lots, each with its own little piece of bush severely modified to reduce bushfire hazard.

Attitudes to vegetation In the past, a common approach to achieving safer landscapes around buildings has tended towards eliminating the problem. In many cases most of the mature vegetation was removed and replaced with exotic plants and garden styles. At present, the advice given on what to do about landscaping around buildings emphasises the need for fuel reduction. The advice about what to plant often lists many imported species, such as English oaks and so on. Many people have been following this course of action for a long time, but it is difficult to tell whether they are doing so for bushfire safety or for cultural reasons. This ‘imported garden’ approach has many attractions and can work successfully, provided there is: • enough space on smaller lots to plant effective barriers of these imported species, • a suitable environment to grow them, and • a reliable supply of water to sustain them. Even if the above three conditions are met, the question arises as to whether this is the best way ahead. It is one which is becoming less favoured in Australia. With increasing appreciation of our native animal and plant life there is a need to develop a more sympathetic approach based on managing the problem rather than eliminating the problem. 41

Landscape design

Despite its reputation, Australian vegetation is not wholly bad when it comes to bushfire attack on buildings. Although it is widely known that many Australian native plants have certain attributes that promote bushfire attack, there are also attributes that help to provide protection to buildings. Furthermore some of the ‘bad’ attributes can be modified — for example by pruning in specific ways without removing the whole plant. In cases where some fire-hazardous attributes are too difficult to modify, removal of the whole plant may be justified. These plants can then be replaced with less fire-hazardous natives which are compatible with the area. As has been mentioned previously some species of native vegetation can be used in a positive way to provide a barrier against bushfire attack provided they themselves can be prevented from igniting in a bushfire. These design techniques need to be reinforced with regular maintenance, particularly the clearing of litter on the ground.

Vegetation management The terms ‘vegetation management’ and ‘manage vegetation’ will be used frequently in this manual and they have quite specific meanings. In general terms, they mean both reducing the opportunities for vegetation to ignite and restricting the spread of fire in vegetation. ‘Vegetation management’ includes a number of techniques. While some of these techniques are design decisions, for example, the choice of type and location of plants, others are regular maintenance techniques. Some vegetation management techniques are described below. • Plant or retain species which have low flammability. For a full explanation of ‘flammability’ see page 30. • Plant or retain species which do not drop much litter in the bushfire season and which do not drop litter that persists as ground fuel into the bushfire season. • Plant or retain species which possess attributes which make them a good barrier against bushfire and wind attack, provided they themselves can be prevented or delayed from igniting. For further information on barrier-forming ability see page 31. • Create discontinuities or gaps in the vegetation to slow down or break the progress of fire towards the buildings, including spread of fire from tree-top to tree-top (so-called ‘crown fires’). This principle is 42

Landscape design

embodied in the requirements of some authorities to provide a fuelfree or fuel-reduced area of prescribed minimum widths. • Reduce the opportunities for a ground fire to burn a pathway up into the canopy of trees (which facilitates crown fires). This can be achieved in several ways:

Removal of lower branches.

Clearing the understorey.

It has been suggested that this be done up to about two metres above the ground.

This restricts the opportunities for a ground fire to ignite lower branches and loose bark.

Removal of loose bark.

Removal of dead twigs, leaves etc.

The removal of loose bark is most effective if done lower down and some distance above understorey vegetation.

Removal is easier to carry out nearer the ground. However, consideration should be given to their removal higher up as well. 43

Landscape design

If trees can be prevented from being ignited by some of the techniques of vegetation management described above, many trees need not be the bushfire hazard they would be otherwise. In fact, the same trees may perform a positive role, acting as a barrier which helps to protect buildings from wind-driven burning debris and wind forces. Knowledge of the characteristics of the various species is the key to the practical application of the techniques of vegetation management. See Chapter 4, ‘Evaluation of vegetation for use in landscaping’ for a description of the performance characteristics of plants.

Robust landscape options Robust design options are those that are likely to remain in place, operating effectively for a very long time with little or no intervention by people and are not likely to be removed by people. While other elements around them may change, the robust elements will remain even though preparedness for bushfire may be far from the minds of the residents. Robustness may be achieved in a number of ways: • Choose a suitable overall landscape style, for example, a park-like setting. • Use options for which a minimum of maintenance is required for them to remain effective, for example, a masonry wall, a noncombustible fence, protective earthwork such as an earth mound, and major protective planting such as a large hedge or shelterbelt planting. • Use elements that satisfy important long term needs, other than bushfire survival, which are therefore likely to be retained and maintained, for example, cleared open spaces such as parking areas, playing fields and large paved areas. • Use elements that are difficult to remove or change, such as a very large hedge, a masonry wall or protective earthwork such as an earth mound.

44

Landscape design

A methodology for landscape design As explained in Chapter 5, ‘Design – general’, the approach taken in this manual is to state the OBJECTIVES and then provide DESIGN OPTIONS to meet them. The DESIGN OPTIONS are worked out by applying PRINCIPLES of design to each of the DESIGN ELEMENTS of the landscape to meet these OBJECTIVES.

Methodology for landscape design

DESIGN OPTION PRINCIPLE DESIGN OPTION OBJECTIVE

DESIGN OPTION DESIGN OPTION PRINCIPLE DESIGN OPTION ETC.

OBJECTIVES The OBJECTIVES of design for any one DESIGN ELEMENT of the landscape will include one or more of the following four OBJECTIVES.

OBJECTIVE 1: Reduce attack by embers and burning debris driven by the wind. Because the major cause of ignition of buildings is attack by embers and burning debris, this objective deserves special attention. Reductions can be achieved by dealing with the plants which are the source of embers and burning debris, clearing litter on the ground near buildings and by providing protective barriers. Embers and burning debris may be generated some distance away from a property and may attack a building regardless of whether fuels are appropriately managed in the immediate vicinity of a building.

OBJECTIVE 2: Reduce attack by heat radiation Although heat radiation may not be a major cause of ignition directly, it does dry out and pre-heat the vegetation and the buildings, making them easier to ignite. Reducing the effect of radiation can be achieved by controlling the type and amount of vegetation used, by barriers and by distancing fuel from buildings. 45

Landscape design

OBJECTIVE 3: Reduce attack by direct flame contact This potential means of ignition is probably the easiest to identify as a hazard, because it requires fuel very close to or in contact with the buildings. The main approach is to keep fuel at an appropriate distance from buildings.

OBJECTIVE 4: Reduce attack by wind The major landscape approach to reducing wind attack is through the use of shelterbelt and windbreak planting and barriers of various other types such as walls, fences and mounds.

PRINCIPLES There are two PRINCIPLES that can be applied to the design of landscape elements to achieve the OBJECTIVES listed above.

PRINCIPLE 1: Manage vegetation In general terms, this means reducing the opportunities for the ignition of vegetation and restricting the spread of fire in the vegetation. There are several techniques for doing this and these are described in ‘Vegetation management’ on page 42.

PRINCIPLE 2: Provide barriers Barriers of various types are useful against all four modes of attack (embers and burning debris, radiation, direct flame contact and wind).

DESIGN ELEMENTS For the purposes of developing DESIGN OPTIONS for the design of the landscape around buildings in bushfire areas, a number of DESIGN ELEMENTS have been identified. These include DESIGN ELEMENTS such as landform, screen planting, and open spaces; a full list is given on page 52 in the next chapter. The figure below illustrates how a DESIGN OPTION may be developed for a DESIGN ELEMENT such as ‘Trees and Shrubs’.

Example of the development of a DESIGN OPTION

46

OBJECTIVE Reduce attack by embers and burning debris driven by the wind

PRINCIPLE

DESIGN OPTION

Manage vegetation

Use plants without heavy litter drop persisting into fire season

Chapter 7: Landscape design options In this chapter, we consider each of the main component elements of the landscape and give options for their design. Designers can adopt any one design option to meet a specific objective and can also use more than one design option in combination, if they choose to do so, because the design options are not mutually exclusive.

Planning requirements – a cautionary note Before proceeding with any proposals the designer should check first to see if there are any planning requirements to be met covering factors such as zoning, siting of buildings and management of vegetation. These are in addition to building regulations and they may vary according to the administrative area, both State and local.

Choosing a suitable lot Landscape design really starts with the choice of a lot because this choice defines the design options possible. This applies to the choice of vacant land for new development and also to the choice of an established lot.

The general locality The choice of a suitable lot is a two-stage process. The first step is to find a suitable general locality. One way of doing this is to consult fire brigades and local government or regional planning authorities who may have maps indicating the fire hazard. These maps vary in the range of factors taken into account but may include one or more of the following: • amount of fuel, • type of fuel, • slope of land, and • aspect of slope.

47

Landscape design options

As well as these, there are many other factors which may be relevant to the risk of the fire. These include: • frequency of fires in the area, • amount of existing development, • accessibility of the area, and • fire fighting facilities. ‘Frequency of fires in the area’, may not be a good indicator of risk. In areas which have frequent fires, fuels are often reduced, fire services are generally better equipped, trained and experienced, and members of the community may be better prepared. Outcomes may be directly opposite in areas which have had very few fires: high fuel loads, a community that is not well prepared, and a fire brigade that is ill-equipped and trained. In these areas, the risk of a fire that causes loss of buildings may be greater. The factor ‘fire fighting facilities’ may be an important variable under moderate fire conditions. However, during severe fire conditions, where most building losses have occurred in the past, fire services may not be in a position to provide adequate protection. This factor may thus be misleading and may encourage a sense of safety which could lead to householders not undertaking the necessary mitigation measures. The safest lots should be in areas which are mapped as not having significant fire hazard. However, this should not be taken to discourage development in areas with some bushfire hazard. The main purpose of this chapter is to provide methods for alleviating the attack of a bushfire on a building through modification of the landscape, especially in areas where some hazard exists. Although the safest lots may be in areas which are mapped as not having a significant fire hazard, it is possible that a poorly designed and/or poorly maintained landscape and building in a low risk area may be more vulnerable to bushfires than a well designed and maintained one in a high risk area.

The individual lot After finding a suitable general locality, the next step towards finding a suitable lot is to consider each of the possible lots for their potential. The advantages and disadvantages of each lot can be listed systematically but in the final analysis it is a personal decision about the relative 48

Landscape design options

weighting which people attach to the various factors — both those that relate to bushfire survival and also all of the others that do not. A sensible balance will need to be achieved between the level of risk and the level of treatment one is prepared to apply.

Analysis of the chosen lot When an individual lot or property has been chosen, you can carry out a detailed ‘site analysis’ as a preparation for designing. This analysis should include all of the factors that might have a bearing on the design of the buildings and their surroundings. The factors which relate to a bushfire attack are listed below. Those factors that tend to alleviate bushfire attack or assist building survival are described as positive (+), and those that tend to promote attack or hinder building survival are described as negative (-). • Potentially protective vegetation barriers. (+) • Space for planting of protective barriers, including suitable distances between barrier and proposed building (see ‘Screen planting’, page 61). (+) • Possible location of protective open spaces such as car parks. (+) • Suitable type and location of additional water supply, such as dams, to supplement town mains supply. (+) • Access and egress routes for people and vehicles. (+) • Hazardous vegetation outside the lot. (-) • Hazardous vegetation inside the lot. (-) • Steep slopes which increase fire speed uphill. (-) • Potential loss of services in bushfire (e.g. overhead wires). (-)

Landscape style When designing or modifying a landscape setting, one may approach the task with an overall style or type of environment in mind — for example, bush setting or exotic garden — rather than tackling one element at a time. The initial choice of a style should take account of its appropriateness to the area and the ability to maintain it because the different approaches vary greatly in the effort and resources needed to maintain them, especially in harsh environments.

49

Landscape design options

Four landscape or garden styles are described below, and then compared (in the table on the opposite page) in terms of various attributes. Some are related to bushfire and others are related to ecological and the visual considerations. The four styles are idealised and in reality a combination of them would be most likely. The selection and location of vegetation would hardly ever be kept to such precise categories and would be chosen to meet a wide variety of needs, preferences and local conditions. For example, on a large property an open park-like landscape approach may be used further away from the buildings and a different approach taken for the closer surrounds of the buildings. The four styles are: • Uncleared bush or forest setting This consists of much flammable vegetation and heavy litter on the ground. Little (if any) control is exercised over the vegetation by people. There are likely to be few open spaces. • Modified Australian landscape This contains mostly native species, some selected for their particular attributes to perform specific functions such as shading or screening. Placement of vegetation is considered and there may be some clearing to create open spaces. • English-style landscape Here much of the native vegetation has been cleared and replaced with low flammability imported species, larger deciduous trees, lawns and open spaces. • Park-like landscape This is characterised by larger trees spaced widely apart, sometimes in clumps or belts, with large spaces between them. There is an absence of understorey plants except in small amounts well away from trees and buildings. Mowing or slashing of grass is made easier by lack of obstructions. Differing individual preferences and changing ownership of properties over time usually result in a wide variety of approaches to landscape and garden designs. A thoughtful, well-informed approach that takes into account at least all major factors is the ideal. When a successful model has been developed for a particular set of circumstances, other people tend to follow. In rural areas, particularly where bushfires have occurred, this process is going on all the time. However, when urban dwellers move to the country they may not have the benefit of such accumulated experience. 50

Landscape design options

Suitability of landscape styles in terms of their attributes

Park-like landscape

English-style landscape

Modified Australian landscape

Uncleared bush or forest setting ✸✸

✸

✓

—

Regrowth, recovery after fire

✓

✓

✸✸

✓

Need for cutting back or mowing due to rapid growth

✸

✸

✓

—

Fire hazardous fuel

Demand on water supply

✓✓

✓

✸✸

✓

Support for native wildlife

✓✓

✓✓

✸✸

✓

Promotes native flora

✓✓

✓✓

✸✸

✓

Fits in visually with native landscapes

✓✓

✓✓

✸

✓✓

✸

✓

✸✸

✓✓

Suitable for smaller lots (e.g. residential subdivisions)

✸✸

✓✓

✓

■

Opportunity for protective screen planting

✸✸

✓

✓

✓✓

Suitability for large areas (e.g. farms, hobby farms)

Key ✓✓ ✓ — ✸ ✸✸ ■

very suitable suitable variable unsuitable most unsuitable suitable for whole sub-division only

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Landscape design options

Design options In the following pages, a number of DESIGN OPTIONS for each landscape DESIGN ELEMENT which might be used in the design of new properties or the alteration of existing properties, are described and illustrated. The DESIGN ELEMENTS covered are: • trees and shrubs (including vegetation under trees), • landforms, • ground cover and mulches, • screen planting, • open spaces (lawns, gravelled areas, paving, parking areas, driveways and paths), and • fences and garden walls. For each landscape DESIGN ELEMENT, there are four OBJECTIVES and two PRINCIPLES relevant to bushfire attack:

OBJECTIVE 1: Reduce attack by embers and burning debris driven by the wind OBJECTIVE 2: Reduce attack by heat radiation OBJECTIVE 3: Reduce attack by direct flame contact OBJECTIVE 4: Reduce attack by wind PRINCIPLE 1: Manage vegetation PRINCIPLE 2: Provide barriers These OBJECTIVES and PRINCIPLES are used to categorise the DESIGN OPTIONS. This design methodology has been discussed in some detail in Chapter 6, see page 45. It is unlikely that any landscape DESIGN OPTION other than the elimination of all vegetation would eliminate the bushfire hazard. Even if all vegetation were eliminated from an allotment, the vegetation outside the boundaries may not be eliminated. Use of the DESIGN OPTIONS presented can only alleviate the hazard and a combination of DESIGN OPTIONS will be most effective. The DESIGN OPTIONS are not mutually exclusive and as many as are appropriate or affordable may be used together.

52

Landscape design options – Trees and shrubs

Trees and shrubs Trees and shrubs can have a dual role in the attack of bushfires on buildings:

OBJECTIVE 1 Reduce attack by embers and burning debris driven by the wind PRINCIPLE 1 Manage vegetation

•

a harmful role by providing fuel for the fire, both on the trees and shrubs, and as the source of litter on the ground; and

•

a protective role by shielding the building from the fire and the wind, provided that the trees and shrubs themselves can be prevented from igniting and becoming part of the attack (see also ‘Screen planting’ on page 61).

Design Option 1: Use low flammability plants Low flammability plants do not ignite easily or burn fiercely. There are many attributes that influence their flammability, some more strongly than others. A full list of these attributes is given on page 32. Even though some of these attributes in one species of tree favour low flammability, some other undesirable attributes, which are weighted more heavily in importance, may override the others and cause that species to be classified as highly flammable. Fine leaves and loose bark would be good examples of this. Similarly some attributes can reduce the overall flammability of a species even though some other undesirable attributes are present. For example, a species may have very dense foliage, but if this is located very high above the ground on a tall smooth trunk, the overall flammability is much reduced.

Design Option 2: Use plants without heavy litter drop persisting into the fire season Bushfires are fuelled in large part by the fuel on the ground. Many Australian native trees and shrubs drop large amounts of litter, including branches, twigs and leaves, especially in the hot dry season.

53

Landscape design options – Trees and shrubs

Trees which drop litter should not be planted or allowed to remain overhanging roofs and roof gutters, or so close that leaves can flutter across onto roofs. If such trees are left near buildings regular clearing will be required. Regular clearing is not a design option in the sense that it is not done in the initial design stage. However, it is always highly important. Regular clearing, as well as cutting back of vegetation, can maintain the effectiveness of good design and neglect can greatly reduce its value.

Design Option 3: Keep space under trees and shrubs cleared of flammable fuel The area under flammable trees should be kept-clear of scrub and long grass to prevent a ground fire pre-heating the leaf canopy above (preheating facilitates ignition). This option includes both planting design and ongoing maintenance. Clearing can be by both controlled burning in safe periods and by mechanical means. Mechanical means includes slashing and mowing. The cut material will decompose more readily when compacted on the ground or it can be composted in a safer place.

Design Option 4: Create large gaps between groups of trees Very large gaps between groups of trees and shrubs may restrict the spread of fire horizontally towards buildings. Partial clearing to create gaps or planting of trees and shrubs in groups with large gaps between them will help to break the spread of fire, although there will still be some combustible material such as grass between the groups.

Design Option 5: Reduce opportunities for upward spread of fire Ground fires can burn up into tree canopies and ignite them although a very intense fire is required to get a crown fire. This upward path of the fire can be restricted by the following means (see figures on page 43): • removal of lower branches, • clearing the understorey, • removal of loose bark, and • removal of dead twigs, leaves etc.

54

Landscape design options – Trees and shrubs

OBJECTIVE 1 Reduce attack by embers and burning debris driven by the wind

Design Option 1: Use trees and shrubs with good barrier-forming attributes Trees and shrubs can be used to provide barriers provided they can be prevented from being ignited and becoming part of the attack. Attributes of plants which favour their barrier-forming ability include: • dense foliage,

PRINCIPLE 2 Provide barriers

• continuous plant form, • low flammability, and • large size. For a full description of barrier-forming ability, see page 31.

Design Option 2: Use groups of plants selected and located so as to deflect winddriven attack Groups of low-flammability plants, if located and shaped correctly, can deflect wind-driven embers and debris, and also the wind forces themselves, up and over buildings. For the location and design of these barriers see ‘Screen planting’ on page 61.

OBJECTIVE 2 Reduce attack by heat radiation PRINCIPLE 1 Manage vegetation

Design Option 1: Create fuel-reduced area around building Heavy concentration of fuel close to buildings should be avoided to prevent high levels of radiation. High radiation can break windows, allowing embers to be blown in. It can also ignite the building directly or assist ignition by other means. High radiation outside a building can be fatal for people trying to escape from the building, especially if the amount of fuel continues to burn long after the fire front has passed. Examples of such situations where heavy concentrations of fuel occur are: • a building in a forest, and • a building close to combustible outbuildings.

55

Landscape design options – Trees and shrubs

OBJECTIVE 2 Reduce attack by heat radiation PRINCIPLE 2 Provide barriers

OBJECTIVE 3 Reduce attack by direct flame contact PRINCIPLE 1 Manage vegetation

Design Option 1: Use low-flammability planting and non-combustible fences and walls Windows are vulnerable to breakage by radiation and could be protected by low-flammability planting close to them. However, this would block views and light. Walls and fences are similarly obstructive and these seem unlikely options in many cases.

Design Option 1: Create clear space around buildings Combustible fuel should not be touching or be close to combustible parts of buildings. Such fuel includes the following: • bushes and shrubs, especially those with attributes which make them very flammable; and • climbing plants in contact with fascia boards, weatherboards, pergolas, posts, beams and trellis; many climbers retain much dead material inside the outer foliage. Combustible fuel may not be just removed but can be replaced by creating more permanent clear spaces such as paths, lawns and paving.

OBJECTIVE 4 Reduce attack by wind PRINCIPLE 1 Manage vegetation

OBJECTIVE 4 Reduce attack by wind PRINCIPLE 2 Provide barriers

56

Design Option 1: Remove wind-vulnerable trees or limbs of trees Trees or limbs which are likely to fall onto and damage buildings in high winds should be removed. Annual inspections should be carried out to determine vulnerability.

Design Option 1: Retain or plant screen planting Wind forces on buildings can be destructive. They can be reduced by retaining or planting screen planting of an appropriate height and located correctly to deflect wind and hot air from the fire up and over buildings (see ‘Screen planting’, page 61).

Landscape design options – Landforms

Landforms Landforms can be either naturally occurring, such as hills, ridges and gullies, or constructed, such as earth mounds, cut-and-fill, terracing, and excavation into or underground.

OBJECTIVE 1 Reduce attack by embers and burning debris driven by the wind PRINCIPLE 2 Provide barriers

Design Option 1: Build underground When buildings are built partly or wholly underground, the earth can be used as a barrier against wind-driven embers and burning debris. This approach can be useful provided the potentially weak points such as doors, windows, skylights and other necessary openings, are protected. However there are a number of disadvantages with underground buildings. • Underground buildings with their extensive waterproofing are likely to be more expensive than conventional buildings. Better value for money all round may be achieved by making a more conventional building safer. • Occupants may have a false sense of security if weak points have not been made safe. • It may be difficult to see the progress of the fire outside and to know when it is safe to go outside. Cellar refuges under buildings have similar drawbacks to those listed above, and people may be trapped if the building burns above them.

Typical weak points in an underground building

57

Landscape design options – Landforms

Design Option 2 : Use earth mounds Earth mounds, if placed correctly, can help to block and deflect embers and wind-driven debris clear of a building in a manner similar to screen planting described on page 61. Advantages of earth mounds are that they cannot ignite and they are also extremely robust. However, large mounds are expensive to construct, occupy a lot of space which might be better used, are likely to obstruct views, traffic and other normal activities, and may interfere with natural surface drainage patterns. Constructing earth mounds using the cut-and-fill method may be the most feasible approach. Earth mound construction using cut-and-fill

Design Option 3: Cut-and-fill, and terrace the ground Cut-and-fill of sloping land in preparation for slab-on-ground floor construction for a new building removes potentially hazardous under-floor spaces. Cut-and-fill of sloping ground for slab-on-ground construction

58

Landscape design options – Landforms

Cut-and-fill and terracing of land can result in retaining walls or embankments which can act as a barrier against a fire burning uphill, particularly a ground fire. This technique can be used for existing buildings (see figure below), irrespective of the floor construction. Cut-and-fill of sloping ground

OBJECTIVE 2 Reduce attack by heat radiation PRINCIPLE 2 Provide barriers

Design Option 1: Build underground Radiation against the external walls of buildings, even those which are clad with weatherboards is not often likely to be a direct cause of ignition, although radiation can pre-heat them for ignition by other means. The expense of building underground would hardly seem justified if done just as a precaution against radiation.

Design Option 2: Use earth mounds Constructed landforms such as these would need to be very high to protect a whole building from radiation, although they could be useful in special circumstances.

Design Option 3: Use existing landforms such as hills and gullies There is limited opportunity to exploit these features but their use could be considered early in the selection of an allotment.

Design Option 4: Cut-and-fill, earth banks, terracing and retaining walls Cutting and filling and terracing across sloping ground helps to block radiation (see figures opposite and above).

59

Landscape design options – Ground cover and mulches

Ground cover and mulches The term ground cover applies to those plants whose foliage grows only close to the ground and includes grasses and ground-creeping plants. It also includes mulches of various types.

OBJECTIVE 1 Reduce attack by embers and burning debris PRINCIPLE 1 Manage vegetation

OBJECTIVE 1 Reduce attack by embers and burning debris PRINCIPLE 2 Provide barriers

Design Option 1: Provide lawns and areas of cut grass Lawns which are cut short do not provide much fuel for the progress of a ground fire, particularly when green. Large areas of grass, including paddocks, can be grazed by live stock or mown or slashed, so that the fuel compacts more readily and decomposes. It may also be burned in safe periods (with appropriate permits), or may be collected and composted. Compost heaps should be contained and located well away from buildings.

Design Option 1: Use ground cover planting Some low flammability plants such as ivy, if planted over sufficiently large areas, may become a partial barrier to embers by providing more resistance than a smooth surface to burning debris blown across the ground. Falling leaves may also lodge in and under the foliage of ground cover plants rather than being blown together and accumulating against buildings.

Design Option 2: Use mulches to maintain moisture content of vegetation Mulches on the ground in gardens helps to maintain water in the ground, thus helping to maintain the moisture content in plants, and keeping them alive. Some mulches such as pine bark, wood chips and pea straw are flammable when dry and provide ready fuel for fire burning on the ground. Such mulches should not be used close to flammable parts of buildings. Pebbles are a non-combustible ground cover. 60

Landscape design options – Screen planting

Screen planting Screen planting such as hedges and windbreaks are often planted for privacy and protection against wind for people, animals and gardens. If suitable plants are used and maintained and the screen planting is located appropriately, such screens can be very cost-effective as barriers against bushfire by catching embers and debris and reducing the force of the wind. Screen planting should not include species that are highly flammable or drop litter which persists into the bushfire season. Screen planting consists of rows of closely-grouped planting, either trimmed as a hedge, or untrimmed. Shelterbelt planting is a form of screen planting used where there is sufficiently large space as on farms, large sub-divisions and lots, and community areas. Where there is sufficient space available, there may be one, two, or three rows of shelterbelt planting.

OBJECTIVE 1 Reduce attack by embers and burning debris PRINCIPLE 2 Provide barriers

Design Option 1: Use species which have good barrier-forming attributes Screen planting can filter out a large proportion of the vast quantity of burning embers and burning debris that are swirled around in the high winds associated with bushfires. To work effectively as barriers, the species used should have good barrier-forming attributes. They should have low flammability and not produce much ground fuel in the bushfire season. These attributes are described fully in Chapter 4 on pages 23 to 29.

Design Option 2: Design and locate screen planting to be most effective All low-flammability vegetation has some barrier-forming capability, particularly if it is managed and maintained to remain of low flammability. To be most effective against ember and burning debris attack, screen planting should be designed and located as explained below and shown in the diagrams.

61

Landscape design options – Screen planting

When winds accompanying a bushfire hit a barrier they are slowed down and also deflected up and over the barrier to descend again some distance downwind. A protected area is created for some distance behind the barrier. If the barrier is very dense, there is some turbulence on both the windward and the leeward sides. On the leeward side some air is drawn down into the reduced air pressure space immediately behind the barrier and some of the air-borne embers and burning debris will be carried with it. A very dense barrier creates turbulent flow

If a dense barrier is slightly permeable, some of the wind will pass through the barrier and tend to restore normal air pressure behind the barrier. The airflow will then be less turbulent over and beyond the barrier for some distance. On the windward side the turbulence can be reduced by sloping that face of the barrier by using plants of gradually increasing heights starting with very low growing species that retain their foliage down to ground level. A slightly permeable barrier creates a less turbulent flow

62

Landscape design options – Screen planting

If a barrier is too close to a building, there is a threat from the radiation and flames if the barrier itself ignites. If the barrier is too far from the building the embers and burning debris will fall into the space before the building or onto it. The objective of the barrier is to deflect the wind and wind-driven embers and burning debris up and over the building. The patterns of wind flow in these situations are well known but there are so many variables affecting each situation that an exact recommendation for the location of barriers cannot be given. One recommendation is that for protection from bushfire, a barrier of dense planting be located within 1.5H and 5H from the building, where H is the mature height of the trees. The maximum protection is obtained immediately behind the barrier but a distance from the building of at least 1.5H is needed. One reason for this separation is the risk of a tree being blown down onto the building. The other reason for keeping a minimum separation of a barrier from a building is the risk of radiation and flame attack on the building if the barrier itself should ignite. Recommended location of a barrier

max 5H min 1.5H

H

If the likely direction of bushfire attack could be predicted (by noting the location of hazardous fuel and also likely wind directions) then the term ‘windward’ as used above would have a specific meaning. However, changes in wind direction during a bushfire, and also the possibility of long-distance spot fires starting ahead of the main fire and burning close to the building both mean that bushfire can attack from any direction. The best barrier is therefore one which surrounds a building on all sides. Such a barrier needs openings for access of course, and these would be a weakness. They could be protected by overlapping them. However, a barrier around all sides may not be practicable or desirable in many cases, and a barrier in the direction of the most likely attack is next best. 63

Landscape design options – Screen planting

OBJECTIVE 2 Reduce attack by heat radiation PRINCIPLE 2 Provide barriers

OBJECTIVE 3 Reduce attack by direct flame contact PRINCIPLE 1 Manage vegetation

OBJECTIVE 4 Reduce attack by wind PRINCIPLE 2 Provide barriers

64

Design Option 1: Use screen planting as a barrier to protect parts of buildings particularly vulnerable to radiation Glass can be cracked and broken by intense heat radiation and barriers of low-flammability planting can alleviate this. The barriers would need to be close to the windows, to be effective, but not so close that the barrier could set fire to the building if the barrier itself should ignite.

Design Option 1: Locate screen planting appropriately Screen planting should be located at a suitable distance from buildings (including outbuildings) so that, if ignited, the flames generated do not contact the buildings.

Design Option 1: Provide screen planting to reduce wind forces on buildings The winds associated with bushfires are very severe and the reduction of them will help to keep buildings intact. It is helpful to locate screen planting in the direction from which fires are most likely to come, given knowledge about bushfire winds for that region, concentrations of fuel nearby and the fire history of the area. However, it is possible for bushfires to attack from all points of the compass, especially when winds change direction suddenly.

Landscape design options – Open spaces

Open spaces Open spaces and clearings can be of great value in the defence against a bushfire, especially if well located as explained below. The choice of landscape design style as described earlier on page 49 will influence the use of open space. Open spaces include lawns, paddocks mown or grazed closely by livestock, gravelled areas, paving, parking areas, driveways and paths.

OBJECTIVES 1, 2 & 3 Reduce attack by embers and burning debris driven by the wind, heat radiation and direct flame contact PRINCIPLE 1 Manage vegetation

Design Option 1: Create open spaces in the area immediately around buildings This can be done using lawns, gravelled areas, paving, parking areas, driveways and paths. Vegetable gardens may also be considered as semi-cleared areas. The use of a fuel-reduced area around a building reduces the attack by wind-driven debris, radiant heat and direct flame contact. A fuel-reduced area around a building also provides an area where air-borne debris can fall without starting new fire outbreaks. The size of the fuel-reduced area will be influenced by the type of vegetation and the slope of the land. The location and size of screen planting to deflect wind up, over and around buildings is given under ‘Screen planting’ on page 61, and this will influence the size of the cleared areas inside that planting. The creation of open spaces within areas of extensive vegetation will break the continuity of tree canopies and help to slow down or stop the spread of fire through the tree canopies. The result would be a series of groups of trees with large gaps between them, giving the appearance of a ‘park-like’ landscape (see page 51). The creation and maintenance of clear driveways and paths is also important to allow egress from buildings and to provide access for fighting fires. A single access and egress driveway or pedestrian path can be blocked by fire. An alternative route may provide an escape route for people and vehicles and also access for firefighters. 65

Landscape design options – Fences and garden walls

Fences and garden walls Non-combustible walls and fences can provide a barrier against all four modes of attack (embers and burning debris, radiation, flame and wind) if they are designed and located correctly. However, combustible fences such as timber and brushwood can provide fuel for the bushfire.

OBJECTIVES 1, 2, 3 & 4 Reduce attack by embers and burning debris driven by the wind, heat radiation, direct flame contact and wind PRINCIPLE 1 Provide barriers

66

Design Option 1: Use non-combustible materials Brick, stone and metal are all suitable. For the location and design of these barriers, see the earlier section on ‘Screen planting’ (page 61). The performance of walls and fences would not be the same as very dense screen planting but there are some similarities.

Design Option 2: Treat timber fences with a fire retardant The fire retardant used should have been proven to withstand weathering.

Chapter 8: Building design This chapter explains the method developed in this manual for designing buildings. Details for building design are given in the next chapter, ‘Building design options’.

The building approach The two previous chapters have described how to design the landscape to reduce the bushfire attack on buildings — the landscape approach. This chapter and the next will describe how to design the buildings to reduce the possibilities of them igniting and being damaged or destroyed in bushfire — the building approach. The landscape approach and the building approach are not mutually exclusive and should be used in combination, the extent of each being determined by each individual situation. The design of the buildings to prevent ignition has to carry most of the responsibility in situations where the landscape surroundings remain hazardous. The points summarised below are from Chapter 5 ‘Design – general’ and relate to building design specifically. They form the basis for the approach used in this chapter and the next. • The safest design for a new development in a bushfire-prone area can be achieved by starting with the landscape design, at least in broad principle, before the building design. • Design for bushfire should be included early in the designing process, at least in broad principle again. • Designers need flexibility and choice in designing — hence the design options approach used in this manual. • Conflict between design for bushfire design objectives and other design objectives can be resolved by trading off design options between them.

67

Building design

• Single-concept solutions on their own, such as building underground or relying on roof-top sprinklers, will still have weak links and a combination of design options is always needed. • Off-the-rack, so called ‘bushfire house’ designs are not adaptable to different sites and may be unnecessarily expensive. • Combinations of landscape design options and building design options, depending on the site and the building design objectives, will yield cost-effective solutions. • Maintenance of landscapes and buildings is always highly important and a supplement to good design. • Robust design options are preferable over those that require ongoing effort and resources.

Exterior refuges A purpose-built exterior refuge for people is often thought to be the answer to providing for safety of building occupants, making improved design for the building itself redundant. However, there are some serious drawbacks to the use of such refuges. • People may be tempted to leave the main building and enter the refuge at the very time when the bushfire attack is most severe and this could be fatal. • Maintenance of an exterior refuge would need to be kept up as the infrequency of bushfires can lead to neglect. • The cost of building an exterior refuge could be high and it may be better to spend that effort and money in making the main building and its surroundings a safer place. This manual does not attempt to provide detailed advice on the construction of exterior refuges because of a lack of definitive knowledge and their inherent drawbacks mentioned above.

Robust building options Robust design options are preferable to those that require ongoing effort and resources. Robust options are those that are likely to remain in place and operating effectively for a long time with little or no intervention by people. 68

Building design

Some building design options are robust because they require little or no maintenance to remain effective. For example, masonry wall cladding, concrete decks, simple outline shape of building and roof form, once adopted, require minimal maintenance. Some other building design options are robust because they do not require people to operate them in the event of a bushfire. They may be described as ‘passive’ design solutions. An example of this is toughened glass in windows rather than shutters. Roof-top sprinklers on the other hand are ‘active’ rather than passive because they generally require people to operate them in the event of a bushfire. They would also require regular maintenance to keep them in working order.

A methodology for building design As explained in Chapter 5, ‘Design – general’, the approach taken in this manual is to state the OBJECTIVES and then provide DESIGN OPTIONS to meet them. The DESIGN OPTIONS are worked out by applying PRINCIPLES of design to each of the DESIGN ELEMENTS of the building to meet these OBJECTIVES Methodology for building design

DESIGN OPTION PRINCIPLE

DESIGN OPTION DESIGN OPTION

PRINCIPLE

DESIGN OPTION

OBJECTIVE DESIGN OPTION PRINCIPLE DESIGN OPTION

DESIGN OPTION PRINCIPLE

DESIGN OPTION ETC. 69

Building design

OBJECTIVES The OBJECTIVES of design for any one ELEMENT of a building include one or more of the following four OBJECTIVES.

OBJECTIVE 1: Reduce ignitions by embers and burning debris driven by the wind Embers and burning debris appear to be the major cause of ignitions and therefore this objective deserves special attention.

OBJECTIVE 2: Reduce ignitions by heat radiation Although radiation is not the most frequent cause of ignition directly, it does dry out and heat combustibles and makes them easier to ignite by other means (embers and direct flame contact). Radiation can penetrate through the glass in windows, and heat the interior. It is important that people are able to take refuge in a building away from excessive radiation through glass. Other effects of heat radiation are the breaking of glass and the melting of plastics such as p.v.c. wall cladding and roof gutters.

OBJECTIVE 3: Reduce ignitions by direct flame contact Many combustible external parts of a building are vulnerable to being ignited when flame is applied to them. The flame may come from some burning vegetation or outbuilding close to the building or from accumulated litter which has caught fire.

OBJECTIVE 4: Reduce wind damage The very strong winds usually associated with bushfires are made worse by the convection currents caused by the hot air rising from the fire and cooler air rushing in to take its place. These winds can damage or loosen parts of a building, roof sheeting or tiles for example, allowing embers and burning debris to enter and ignite building contents. The winds may also carry debris heavy enough to break windows, again opening up the building to ember and burning debris attack.

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Building design

PRINCIPLES There are four PRINCIPLES that can be applied to the design of building ELEMENTS to achieve the OBJECTIVES listed above.

PRINCIPLE 1: Minimise litter and ember accumulation points These points are described and illustrated in Chapter 3 ‘Ignition and destruction of buildings’ on page 14. These are of great importance.

PRINCIPLE 2: Minimise use of combustible materials externally Wood is by far the most common combustible material used externally on buildings in Australia. It is much more vulnerable when it is split, rotting or has a rough (off-the-saw) finish.

PRINCIPLE 3: Prevent entry of embers and burning debris driven by the wind Wind-driven embers and burning debris can enter in or under a building before, during, and after a bushfire. They enter through small openings such as gaps in the roof covering or through openings made when wall cladding or roof fixings are loosened by the wind. They can also enter through windows which have been broken by radiant heat or wind driven objects.

PRINCIPLE 4: Provide and maintain services Services include the means for fighting the fire such as mains water supply, emergency water storage, water pumping and electric power. Telephone and TV communications can provide information to and from occupants of a building.

DESIGN ELEMENTS For the purposes of designing or altering a building to survive bushfire, the building may be considered as consisting of a number of DESIGN ELEMENTS such as plan shape, roof profile and underfloor spaces. A full list of the DESIGN ELEMENTS will be given in the next chapter, ‘Building design options’.

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Chapter 9: Building design options In this chapter each of the main component elements of buildings in bushfire areas will be considered and options given for their design. Designers can adopt any one design option to meet a specific design objective and they can use more than one design option in combination if they choose to do so. In addition to the principles given here, there are two primary sources of information, Australian Standard AS 3959, Construction of Buildings in Bushfire-prone Areas, and Standards Australia Handbook, SA.HB36 (1993), Building in Bushfire-prone Areas.

Building regulation requirements — a cautionary note Before proceeding with any proposals, designers should check first to see if there are any building regulation requirements to be met in regard to bushfire design. These may vary according to the administrative area covered. The Building Code of Australia is nationwide, but there may be State or local government variations. However, the design options can also be used in an ‘alternative solution’ under the BCA performance approach.

Design options In the same way that the landscape design options in Chapter 7 are intended to give designers choices and the opportunity to be flexible in their approach, this chapter is intended to provide similar opportunities for choice in the design and modification of buildings that fit in with their other design objectives. Designers do not work by considering each element in isolation from other elements. The method presented in this manual, in which different options are offered to overcome difficulties that may arise with an element, allows designers to trade off between different options for different elements to find a balance that suits them best. 72

Building design options

In some situations, a number of troublesome elements might be eliminated by taking a broader view of things. For example, a complex roof shape with inward slopes, internal gutters, difficult junctions and numerous leaf litter accumulation points could be replaced with a simple outward-sloping roof with external eaves gutters In the following pages, a number of options for each building element, which might be used in the design of new buildings or the alteration of existing buildings, are described and illustrated. These BUILDING DESIGN ELEMENTS are: • plan shape, • roof profile, • roof cladding, • roof gutters, • floors and underfloor spaces, • verandas, decks, steps, landings, pergolas and trellis, • walls, • windows, doors and vents, • outbuildings and storage facilities, and • services. For each building DESIGN ELEMENT, the relevant OBJECTIVES and PRINCIPLES are used to categorise the DESIGN OPTIONS (see table on next page). This design methodology has been discussed in some detail in Chapter 8. Some of the four design principles are not applicable to all of the objectives. For example, preventing the entry of embers and burning debris (PRINCIPLE 3) has no significant effect on the reduction of attack by direct flame contact from the bushfire (OBJECTIVE 3). In some instances, a design option has the capacity to eliminate vulnerability to ignition or damage. In others, an option may only alleviate the vulnerability. Elimination is obviously preferable to alleviation and this distinction is made in discussing design options in the following pages. For example, ignition in underfloor spaces can be eliminated by the use of slab-on-ground construction, whereas, enclosing the underfloor spaces, may only alleviate the vulnerability. 73

Building design options

Availability of design options for a building in terms of objectives and principles

PRINCIPLE 1

PRINCIPLE 2

PRINCIPLE 3

PRINCIPLE 4

Minimise litter and ember accumulation points

Minimise use of combustible materials externally

Prevent entry of embers and burning debris driven by the wind

Provide and maintain services

✓

✓

✓

✓

Reduce attack by heat radiation

–

✓

–

✓

OBJECTIVE 3

✓

✓

–

✓

–

–

✓

–

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind

OBJECTIVE 2

Reduce attack by direct flame contact

OBJECTIVE 4 Reduce wind damage

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Building design options – Plan shape

Plan shape Decisions about the shape of a plan are only taken at the beginning of a building program or when alterations and additions are contemplated. Generally speaking a relatively simple plan shape has the potential to eliminate many ignition points at the outset.

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind PRINCIPLE 1 Minimise litter and ember accumulation points

Design Option 1: Use a plan shape with as few re-entrant corners as possible A simple plan shape without re-entrant corners is preferred to a plan shape with multiple re-entrant corners. Problems can occur at these re-entrant corners when bottom edges of walls meet horizontal surfaces such as the ground or the top of a deck or verandah.

A plan without re-entrant corners (left) and plans with re-entrant corners (circled)

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind PRINCIPLE 2 Minimise use of combustible materials externally

Design Option 1: Use non-combustible materials at re-entrant corners The problems with re-entrant corners can be overcome if non-combustible materials are used in these corners. However, complicated plan shapes with re-entrant corners can lead to complex roof forms which may be undesirable (see Roof profile, page 76).

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Building design options – Roof profile

Roof profile The roof profile is largely dictated by the plan shape of a building. However, there are many instances where unnecessarily complicated roof profiles are placed on relatively simple plan shapes. A complicated roof profile will inevitably bring with it a number of details which are potential ignition points. The aim should be to have a roof which is self-shedding of litter and debris. It has been suggested that low-pitched roofs are preferable to steeper sloping roofs because the lower slope is less subject to radiation but there is no evidence to substantiate this. Steeper roofs are more able to shed litter.

OBJECTIVE 1 Reduce ignition by embers and burning debris driven by the wind PRINCIPLE 1 Minimise litter and ember accumulation points

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Design Option 1: Simplify roof profile This may be achieved by sloping the entire roof outwards in a continuous fashion without breaks in profile. Internal gutters and parapet gutters collect litter and embers especially if trees overhang the building or are close to it (within leaf fluttering distance). Fires can start there out of sight and access may be difficult as well. The figure opposite shows undesirable roof profiles and how they can be simplified.

Building design options – Roof profile

Simplify undesirable roof profiles: circles indicate the ember and burning debris accumulation points

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Building design options – Roof profile

When additions are made to existing buildings the new roof is often made nearly flat because of the need to maintain enough ceiling height inside. The junction of the new roof with the existing building is extremely vulnerable due to the accumulation of leaf litter there. It can be made worse by the junction being out of sight under the eaves of the old roof and hard to get at. One option is not to use an almost flat roof for the addition but to cut back into the existing roof and match the slope of the new roof with the old (see the figure below). This has the disadvantage of producing valley gutters but these can be designed to alleviate any problems (see next section on Roof cladding, page 79).

Roof profile for an extension showing non-preferred option (left) and preferred option (right)

OBJECTIVE 1 Reduce ignition by embers and burning debris driven by the wind PRINCIPLE 2 Minimise use of combustible materials externally

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Design Option 1: Use non-combustible materials at ember and burning debris accumulation points The problems with the roof profiles shown in the figures above (and on the previous page) can be alleviated if non-combustible materials are used at the points circled in the figures. Where timber fascias, barge boards etc. are needed for structural reasons or for fixings, they may be protected by a non-combustible material (such as sheet metal).

Building design options – Roof cladding

Roof cladding Many fires in buildings start on roofs and in roof spaces where they may progress undetected until it is too late to extinguish them. Leaf litter and embers and burning debris can be blown through gaps in and around the roof cladding and build up inside the roof space. Leaf litter can build up inside a roof space over a long period before a bushfire and be ignited by embers during the bushfire. Roof tiles may lift off in high winds and may crack if limbs fall on them. Sheeted roofing may also loosen in high winds, allowing embers and burning debris to enter the roof space. The more steep the slope of a roof, the more it will shed litter and embers and burning debris but this will only alleviate the problems and sealing of the roof space is still necessary. To establish and maintain a sound roof covering is therefore very important and all cladding should be fixed securely and sealed in accordance with manufacturers recommendations. There are three main types of roof cladding: • tiles, • sheeted roofing, and • timber shakes and shingles. Timber shakes and shingles are not suitable for use in bushfire areas and are not considered here.

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Building design options – Roof cladding

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind

Design Option 1: Replace or protect timber components adjacent to areas where debris and embers could accumulate Timber used for fascias, bargeboards, etc. can be replaced with metal or protected with non-combustible material such as sheet metal.

PRINCIPLE 2 Minimise use of combustible materials externally

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind PRINCIPLE 3 Prevent entry of embers and burning debris driven by the wind

The preferred location of sarking for tiled roofs (top) and metal sheeting roofs (bottom).

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Design Option 1: Provide sarking All roofs should be provided with sarking over the whole roof area as a barrier against embers and debris which may penetrate gaps in the roof covering. The sarking used should have flammability properties which conform to the requirements of the current Australian Standard. The figures below show the preferred location for the sarking of eaves and ridges for tiles and sheeted roofing respectively.

Building design options – Roof cladding

Design Option 2: Seal the roof space Where roof cladding is penetrated to provide for roof vents, ventilated ridges, evaporative air conditioning systems, skylights and the like, measures should be taken to prevent entry of embers using appropriate flashing and sealing techniques. In addition, attention needs to be given to the sealing of vulnerable areas such as ridges and eaves which are common to most roofs. In the case of tiled roofs, there are at least two methods. The first is to use a thin layer of flexible pointing over the conventional mortar pointing to alleviate the cracking of the mortar at ridge cappings, hips and valley gutters. The second method is to use a dry self-adhesive fixing strip; such strips are available in different shapes to match popular tile profiles. For sheeted roofing, sealing of gaps can be done in a variety of ways and as shown in the figures below.

Ridge cappings and across-the-slope flashings for corrugated (left) or ribbed (right) sheeting are notched out and turned down

Eaves gaps in corrugated roofing (left) are sealed with profiled non-combustible, nonabsorbent filler strips Eaves gaps in ribbed roofing (right) are sealed with rib end-stops

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Building design options – Roof cladding

Design Option 3: Protect roof lights Thermoplastics materials used for roof lighting may melt and fall away under high heat loads, thus allowing the entry of embers and burning debris. The Australian Standard AS 3959 provides measures, including the use of a special glass diffuser at ceiling level, to protect the interior of the building.

OBJECTIVE 4 Reduce wind damage PRINCIPLE 3 Prevent entry of embers and burning debris and driven by the wind

Design Option 1: Design and construct roof cladding and its supporting structure to withstand gale-force winds Weaknesses in roof cladding design, installation and maintenance can suddenly be exposed in a bushfire by extreme wind forces. Manufacturers recommendations for gale-force winds should be followed. All fixings should be inspected and maintained regularly to check for any looseness of the roof cladding. Sealing the cladding as described above also reduces the opportunity for wind to loosen it.

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Building design options – Roof gutters

Roof gutters Roof gutters are a natural accumulation point for litter and embers both before and during a bushfire. Their design, size, construction, visibility and accessibility for regular clearing are therefore important.

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind PRINCIPLE 1 Minimise litter and ember accumulation points

Design Option 1: Eliminate roof gutters In locations where the collection and disposal of roof drainage water is not required, as in a picnic shelter for example, roof gutters can be eliminated provided the roof profile is outward sloping, not inwards towards internal gutters or behind parapets. If collection and disposal of water is required, water from the roof can be collected in pebble or rubble-filled trenches with agricultural pipes at the bottom of the trenches

Elimination of roof gutters and collection of water in a trench

Design Option 2: Avoid narrow gutters It is difficult to clear leaves and other combustible debris from narrow gutters. Narrow valley gutters, especially those with uneven projections of roofing materials, provide places which will readily trap embers and leaf litter.

Design Option 3: Make roof gutters readily visible and accessible Roof gutters which are out of sight or are not readily accessible (for example, gutters behind parapet walls) are not likely to be cleared of litter frequently enough, if at all. For high gutters which are difficult to reach, permanent access, such as a ladder stored nearby, can be provided.

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Building design options – Roof gutters

If downpipes and rainwater drains become blocked, the litter in the roof gutters will not drain away and will build up. One method of keeping downpipes clear is to discharge the downpipe into a drain which is topped by a grating, with a gap between the downpipe and grating. This enables leaves to clear and the proper functioning of the downpipe to be seen. Discharge of rainwater into a drain covered by a grating

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind PRINCIPLE 4 Provide and maintain services

Design Option 4: Use covers or filters over roof gutters to reduce entry of litter Various devices, including the following, are available: • sheet metal covers • metal and plastic meshes • slotted plastic guards All of these covers and filters may allow some litter to enter the gutter and litter may also collect on top of the device. Regular maintenance is therefore still needed.

Design Option 1: Provide for blocking the downpipes and filling the roof gutters with water A well-known technique is to block off circular downpipes with tennis balls or a piece of rolled cloth and fill the roof gutters with water before the fire front arrives. The availability and correct placing of taps with hoses, appropriate blocking devices and ladders (or other means of access ) are needed to facilitate the use of this technique. A blocking device nearer ground level may be an alternative but this requires that all joints above the blocking device are sealed, including the joint between the gutter and downpipe.

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Building design options – Floors and underfloor spaces

Floors and underfloor spaces Floors and underfloor spaces are often out of sight and their maintenance neglected. During a bushfire attack, embers and burning debris can be blown in and ignite unprotected combustible floors and their supports and any combustible items which may have accumulated or been stored there. Buildings are often constructed high above the ground either to capture a view or to deal with steeply sloping ground, or both. The spaces under these ‘elevated buildings’ often contain considerable quantities of combustible items which, if ignited, put the building at risk.

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind PRINCIPLE 1 Minimise litter and ember accumulation points

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind PRINCIPLE 2 Minimise use of combustible materials externally

Design Option 1: Eliminate underfloor space This can be achieved by the use of slab-on-ground floor construction. Although this can be done most readily on level ground, sloping ground can be cut-and-filled to provide a level support.

Cut-and-fill provides a level building surface

Design Option 1: Replace or protect combustible floors with non-combustible material Concrete floors are not limited to level ground and can be built above sloping ground using formwork on which to pour the concrete. Line the underside of timber floors with non-combustible material. Cement sheeting is one possible non-combustible material to use.

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Building design options – Floors and underfloor spaces

Design Option 2: Use non-combustible materials for walls, columns and posts which support floors Concrete, concrete block, stone and brick are suitable for supporting floors. Steel is non-combustible but may distort under intense heat.

Design Option 3: Protect combustible columns and posts Timber columns and posts can be protected by any one of the following: 1 protective metal sheathing, minimum thickness 0.6 mm extending to at least 300 mm above the ground; the metal should be suitably protected from rusting, e.g. by galvanizing; 2 mounting on galvanized metal supports with a minimum clearance of at least 100 mm for the timber above the ground; 3 mounting on top of concrete footings which project above ground level at least 300 mm; and 4 treating the timber with a fire retardant, proven to withstand weathering, for at least 300 mm above the ground. Combustible posts can be protected in a variety of ways

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind PRINCIPLE 3 Prevent entry of embers and burning debris driven by the wind

Design Option 1: Enclose spaces under timber floors with non-combustible materials The space between the ground and floor can be enclosed by either masonry or non-combustible sheeting. Sub-floor ventilation is required and openings such as sub-floor vents and weep-holes should be covered with noncorroding fine mesh to prevent entry of embers. All other openings, such as sub-floor access doors and wall penetrations for pipes, should be sealed to prevent entry of embers and debris driven by the wind. This option is more suitable for buildings on stumps rather than elevated buildings because enclosing the underfloor space can be costly for the latter.

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Building design options – Verandahs, decks, steps, landings, pergolas and trellis

Verandahs, decks, steps, landings, pergolas and trellis All of the above attachments to buildings are often made of timber and can provide horizontal, or near-horizontal, surfaces on which litter can build up before a bushfire and embers and burning debris can lodge during a fire. The hazard is increased when the horizontal surface, a deck for example, abuts a combustible vertical surface such as a timber wall, a timber door or a window frame. In addition, these attachments, if made of timber, are prone to ignition by radiant heat and flames. Once ignited, they can transfer the fire to the building itself or heat the building, making other combustible elements more prone to ignition

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind

Design Option 1: Eliminate vulnerable junctions Attachments such as verandahs and pergolas may abut a vertical surface, such as a wall, and create areas where embers and burning debris may lodge and cause ignitions. These junctions may be removed by redesign.

PRINCIPLE 1 Minimise litter and ember accumulation points

Elimination of accumulation points on verandahs

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Building design options – Verandahs, decks, steps, landings, pergolas and trellis

Design Option 2: Eliminate or minimise the use of attachments to the building Consideration should be given to how essential these attachments really are. In some cases, one or more attachment may be eliminated or replaced by an alternative which serves the same function. For example, extending the eaves overhang may provide the summer shade given by a pergola. Elimination of unnecessary attachments

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind PRINCIPLE 2 Minimise use of combustible materials externally

Design Option 1: Use non-combustible materials Non-combustible materials, such as masonry, cement sheet or steel, may be used for the construction of these attachments. Where attachments with horizontal surfaces, such as decks and landings (combustible or not), abut combustible vertical surfaces, such as timber walls and doors, non-combustible materials, such as sheet metal or cement sheeting, should be used to protect the vertical surfaces for at least the lower 300 mm.

Design Option 2: Separate the attachment from the building Although this option does not stop the attachment from igniting, it does mean that any ignition and burning of the attachment is not readily transferred to the building if the attachment is placed at a suitable distance. Decks, landings, pergolas and trellis may sometimes be treated as part of the landscape around a building and may be separated from the main building.

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Building design options – Verandahs, decks, steps, landings, pergolas and trellis

Decks, landings, pergolas and trellis may be separated from the main building

Some attachments, such as steps and decks, may need to be connected to the building in order to fulfil their function. This could be done using noncombustible materials, such as concrete paving or steel gratings, to form a link with the building. Non combustible materials should be used to connect to the building

OBJECTIVES 2 & 3 Reduce ignitions by heat radiation and direct flame contact

Design Option 1: Use non-combustible materials See discussion above on this Design Option.

Design Option 2: Separate the attachment from the building PRINCIPLE 2 Minimise use of combustible materials externally

See discussion above on this Design Option.

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Building design options – Walls

Walls Although vertical, timber wall claddings are still subject to ignition by embers and burning debris driven by the wind, particularly where the wall meets a horizontal surface and if the cladding is rough-sawn, splintered, cracked, weathered or decayed. Damage to wall cladding materials, such as timber, PVC or cement sheet, by radiant heat or objects carried by the wind can allow embers and burning debris to enter the building. Timber cladding may also be ignited by radiant heat and flame contact but the risk of this happening, particularly if suitable landscaping measures are used, is generally small.

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind

Design Option 1: Eliminate vulnerable junctions The walls may form junctions with other building elements where embers and burning debris may lodge and cause ignitions. These junctions may be removed by redesign.

PRINCIPLE 1 Minimise litter and ember accumulation points

Minimising litter accumulation points at walls

Design Option 2: Coat timber cladding Embers and burning debris can be trapped on rough sawn, splintered, cracked, weathered or decayed timber. Filling and painting the timber provides a smoother surface to minimise this entrapment and also reduces decay of the timber.

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Building design options – Walls

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind PRINCIPLE 2 Minimise use of combustible materials externally

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind

Design Option 1: Use materials which are non-combustible Brick, stone, concrete block, pise, rammed earth, steel and aluminium are all non-combustible. They also have the advantage of requiring little or no maintenance. Timber walls may abut horizontal or near-horizontal surfaces, such as the ground, a verandah roof, a deck, or projections from the walls, to form junctions on which embers and burning debris can accumulate. In such cases, the first 300 mm of the wall may be clad with a non-combustible material such as sheet metal or cement sheeting.

Design Option 1: Provide sarking Walls clad with material such as timber, PVC or cement sheet, which are subject to damage by radiant heat or by wind-born objects, should have sarking installed in the wall cavity. The sarking material used behind wall cladding should meet the requirements of the current Australian Standard.

PRINCIPLE 3 Prevent entry of embers and burning debris driven by the wind

It is good practice for all framed walls to be sarked because the cladding may have gaps and service penetrations which could allow the entry of embers and burning debris.

OBJECTIVES 2 & 3 Reduce ignitions by heat radiation and direct flame contact

Design Option 1: Use materials which are non-combustible See discussion above on this Design Option.

PRINCIPLE 2 Minimise the use of combustible materials externally

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Building design options – Doors, windows and vents

Doors, windows and vents All openings in walls have particular problems associated with them. For example, doors are often made from combustible materials, have gaps under them and thresholds on which embers and burning debris may accumulate. Glass doors and windows are liable to break under the impact of heat and wind-borne objects, thus allowing the entry of embers and burning debris, and the frames are often made from combustible materials. Vents and other small openings provide opportunities for the entry of embers and fine burning debris.

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind PRINCIPLE 1 Minimise litter and ember accumulation points

External doors, windows (or an insect screen) flush with the external edge of the threshold or sill

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Design Option 1: Protect door thresholds and window sills External doors and windows should be flush with the external edge of thresholds and sills to prevent litter and ember accumulation on these horizontal surfaces. Installation of an insect screen on the external edge of the threshold or sill is a suitable alternative.

Building design options – Doors, windows and vents

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind PRINCIPLE 3 Prevent entry of embers and burning debris driven by the wind

Design Option 1: Use special glass to prevent breakage Toughened glass can be used in doors and windows but information about the performance of laminated glass in bushfire conditions is not available. Wired glass is suitable but its use may be restricted to bathrooms, laundries and the like because of its appearance and its obstruction of views. Glass bricks could be used where only light is needed, not a view. Another option is to use glass in small panes so that they are less likely to break.

Design Option 2: Use shutters to prevent breakage Shutters of various types can be used outside doors and windows to protect the glass. Although shutters can be very effective, they have the disadvantage of being an ‘active’ system ( as opposed to ‘passive’ ) because they require people to close them ( and to maintain them between bushfire seasons ). Shutters, however, provide the additional benefits of shade in hot weather and heat retention in cold weather. The best types of shutters are those made from non-combustible materials such as steel or aluminium. They maybe either hinged, sliding or roll-down with the latter having the advantage that they generally have slots which enable people to see what is happening outside during the passage of a bushfire front.

Design Option 3: Use metal mesh insect screens to prevent breakage It is common for doors to have metal screen doors fitted on the outside to protect against insects. Such doors are suitable for bushfire protection if the screen is made from non-rusting metal mesh, of aperture size not more than 2 mm, and a self-closing device is fitted. Normally insect screens are fitted only to opening window sashes but all windows should have such protection (preferably on the outside) using non-rusting metal mesh of aperture size not more than 2 mm. Minor openings in walls include room wall vents, sub-floor vents, weep holes and exhaust fan openings. These should all be screened using nonrusting metal mesh of aperture size not more than 2 mm.

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Building design options – Doors, windows and vents

Design Option 4: Install weatherstripping Doors should be weatherstripped, as shown in the figure below, to seal the gaps under the doors. Weatherstripping doors

OBJECTIVES 2, 3 & 4 Reduce ignitions by heat radiation and by flame contact and reduce wind damage

Design Option 1: Use special glass to prevent breakage See discussion above on this Design Option.

Design Option 2: Use shutters to prevent breakage See discussion above on this Design Option.

PRINCIPLE 3 Prevent entry of embers and burning debris driven by the wind

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Design Option 3: Use metal mesh insect screens to prevent breakage See discussion above on this Design Option.

Building design options – Outbuildings and storage facilities

Outbuildings and storage facilities Most buildings have outbuildings and other types of outside storage facilities associated with them. These include detached garages, garden sheds and sheds used for various agricultural purposes. The ignition of outbuildings and storage facilities can add to the bushfire attack on the main building, especially if they are close. Outbuildings and storage facilities are often built to lower standards than the main building and may even lack doors or window glazing, especially if the openings are large. Basic firefighting equipment may also be lacking and maintenance of these buildings may be neglected. The storage of combustibles such as paper, wood, rags and flammable liquids is common on or near the floor of such buildings, making them even more vulnerable to ignition in a bushfire. The problem of burning outbuildings and storage facilities acting as a source of ignition for the main building can be solved, to some extent, by locating the buildings as far apart as is convenient. However, embers and burning debris from a burning outbuilding or storage facility will still pose a threat to the main building. Therefore, attention still needs to be paid to the design of outbuildings and storage facilities to improve their performance under bushfire attack The Design Options for outbuildings are substantially the same as those for the main buildings already described but there are several other Design Options that may be used. The following section emphasises these other Design Options.

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Building design options – Outbuildings and storage facilities

OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind PRINCIPLES 1, 2 & 3 Minimise litter and ember accumulation points and combustible materials externally; prevent entry of embers and burning debris driven by the wind OBJECTIVE 1 Reduce ignitions by embers and burning debris driven by the wind

Design Options: As for main building already described Attention needs to be given to the provision of doors and window glazing. For large openings, various types of doors are available, including lift-up, roller shutter, horizontal sliding, horizontal folding (concertina) and around-the-corner folding and sliding doors. Gaps under and around the doors should be sealed with suitable devices such as flexible flaps or strips. In addition, facilities such as cupboards and shelves should be provided so that combustible materials are stored well above floor level (where embers and burning debris might accumulate if the seals fail).

Design Options: As for the main building described in the next section Firefighting facilities such as taps and hoses that are long enough to reach the outbuildings should be provided.

PRINCIPLE 4 Provide and maintain services OBJECTIVES 2 & 3 Reduce ignitions by heat radiation and direct flame contact

Design Options: As for the main building already described

PRINCIPLE 2 Minimise the use of combustible materials externally OBJECTIVE 4 Reduce wind damage PRINCIPLE 3 Prevent entry of embers and burning debris

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Design Options: As for the main building already described

Building design options – Services

Services There are a number of services which are considered separately below. They include water, electricity, gas, telephone, radio and television. The protection and maintenance of all of these services are important.

Water An adequate and reliable supply of water could be critical to the survival of buildings in a bushfire. It is highly desirable to have an alternative source of supply because, during a major fire, the town water supply may fail or lose pressure. Even if there is an adequate water supply, its distribution should be kept intact and reliable.

Design Option 1: Provide alternative sources of supply Alternative sources may be dams, swimming pools, and storage tanks filled from roof drainage. These alternative sources will generally require a pumping device if they are to be used effectively: • Diesel driven pumps are the best option. • Petrol engines may be cheaper and more readily available than diesel but, unless protected from radiant heat, they are prone to stoppages caused by fuel vaporisation. • Electric pumps may be cut off from power supply during a fire but a generator (using diesel or petrol as fuel) can be used to provide emergency power.

Design Option 2: Protect piping from damage by heat. The use of metal piping is preferred but plastic piping may be used below ground.

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Building design options – Services

Design Option 3: Provide fire fighting facilities Taps and hoses that reach all parts of the main buildings and outbuildings should be provided. However, because plastic hoses may be damaged by heat, their length should be minimised by installing multiple taps (including taps located near outbuildings).

Electricity The electricity supply may be interrupted during a bushfire for a number of reasons. Overhead supply wires are vulnerable to strong winds which may cause short-circuiting and blow trees against wires, damaging them. Timber poles carrying the wires may be ignited and collapse, breaking the wires. In addition, the supply may be disconnected by the authorities for the safety of those nearby and to prevent ignition of vegetation.

Design Option 1: Put supply wires underground Although expensive, this option prevents damage to the wires discussed above and should be used, at the least, for new sub-divisions and allotments

Design Option 2: Provide an electricity generator A generator will enable electricity to be maintained to operate pumps, lighting and communications. Generators with a diesel engine are preferable to those with petrol engines (see discussion under Design Option 1 for ‘Water’ above).

Design Option 3: Manage vegetation to keep it clear of overhead wires This should be done in accordance with the regulations and recommendations of supply authorities by qualified people (because of the danger of electrocution). The management of vegetation is helped by planting only species with suitable growth habits.

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clearance space

Building design options – Services

Design Option 4: Prevent ignition of poles supporting overhead supply lines This may be achieved by using non combustible poles or by protecting timber poles with a sheet metal collar up to at least 300 mm above ground level.

Gas The loss of the gas supply during a bushfire may only cause inconvenience but the rupturing of supply pipes or storage cylinders due to the bushfire attack could cause ignition of buildings.

Design Option 1: Locate and fix storage cylinders in a safe manner Storage cylinders must be installed in accordance with the applicable regulatory requirements. In any case, they should be located at a suitable distance form the building and have an underground supply to the building. Cylinders should be secured to stop them falling over, and the pressure relief valve should point away from any combustible material on or near the building.

Design Option 2: Provide protection for storage cylinders Non-combustible enclosures such as low brick walls or metal screens will protect gas storage tanks from intense radiation.

Design Option 3: Protect supply lines from damage by heat All piping should be buried and, where exposed, be made of metal (not plastics).

Telephone A telephone provides an essential avenue for communication and information during a bushfire emergency. Cordless phones, phone/faxes and answering machines require electric power, whereas a conventional telephone requires only the telephone line to remain functioning. Mobile phones are independent of both.

Design Options: The Design Options for the protection of telephone wires are the same as Design Options 1, 3 and 4 for ‘Electricity’ discussed above. 99

Building design options – Services

Radio and television Radio and television provide essential information during a bushfire emergency. Generally both require electric power but radios are frequently battery operated.

Design Option 1: Provide an electricity generator See Design Option 2 for ‘Electricity’ above.

Design Option 2: Provide appropriate fixing for antennas Antennas for radio and television reception should be securely stayed against high winds, and fixed to non-combustible parts of the building.

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Glossary

burning debris

flaming or smouldering branches, twigs, bark or other pieces of ignited material

bushfire

a fire involving grass, scrub or forest (also known as a ‘wildfire’)

cladding

the material which forms the external surface of a building over wall or roof framing

combustion

exothermic reaction of a substance with an oxidizer, accompanied by flames, or glowing, or emission of smoke

conduction

the flow of heat through a body by the transference of energy from molecule to molecule without mixing

convection

the transfer of heat by the circulation or movement of heated liquid or gas

crown fire

a fire spreading from tree to tree in their upper foliage

embers

small particles of ignited material

fascia

a board or panel fixed to the outer end of the rafters and to which the roof gutter is usually fixed

fire front

the leading edge of a moving fire

fire hazard*

the potential for loss of life or damage to property by fire

fire retardant

a substance or a treatment, incorporated in or applied to a material, which suppresses or delays the combustion of that material under specified conditions

fire risk

the probability of a fire hazard being realised

flammable

capable of burning with a flame

ignitability

the ease with which a material ignites

radiation

the transfer of thermal energy by electromagnetic waves

re-entrant corner

the internal angle formed between two vertical surfaces

sarking

a sheeting of waterproof material used beneath the roof covering or behind the wall cladding

* Another interpretation of the term ‘fire hazard’ which is used by fire fighting bodies, is the potential severity of a fire.

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References and further reading Anon. (1991) ‘Tree planting for fire protection on farms’ in The Fireman – Operations supplement No. 229, Country Fire Authority, Melbourne. Barber, J.R. and Morris, W. (1980, 1983) Bushfire Protection for Rural Houses. Ministry for Planning and Environment, and Country Fire Authority, Melbourne. Barrow, G.J. (1945) ‘A Survey of Houses Affected in the Beaumaris Fire, January 14, 1944’. J. CSIR, 18 (1). Campbell, R., Chandler, R. and Thomas, G. (1988) Victoria Felix: Improving Rural Land with Trees. Department of Conservation Forests and Lands, and Monash University, Melbourne. Cheney, N.P. (1981) ‘Fire behaviour’, in Fire and the Australian Biota. (Eds A.M. Gill, R.H. Groves and I.R. Noble), Australian Academy of Science, Canberra, pp. 151–175. Cheney, N.P (1985) ‘Living with fire’ in Think Trees, Grow Trees. Australian Government Publishing Service, Canberra, pp. 69–85. Cole, R.E. (1983) Houses Exposed to Bushfires. A Survey of the Hobart Fire of 1967 and the Blue Mountains Fire of 1968. Technical Record 390 (L), Experimental Building Station and Department of Housing and Construction, Chatswood. Douglas, N. (1983) ‘After Ash Wednesday’. Habitat, Australian Conservation Foundation, June. Downes, R.G. (1983) Fire, Vegetation and Houses. Garden State Committee, and Department of the Premier and Cabinet, Melbourne. Gill, A.M., Moore, P.H.R. and Armstrong, J.P. (Eds) (1991) Bibliography of Fire Ecology in Australia. Department of Bush Fire Services, Sydney. King, N.K. and Vines, R.G. (1969) Variations in the flammability of the leaves of some Australian forest species. CSIRO Aust. Div. App. Chem, Mimeo. Rep. Luke, R.H. and McArthur, A.G. (1978) Bushfires in Australia. Australian Government Publishing Service, Canberra. McArthur, A.G. (1968) ‘Rural fire protection’ in Growing Trees on Australian Farms, Department of National Development, Canberra. McArthur, A.G. (1972) ‘Fire control in the arid and semi-arid lands of Australia’, in The Use of Trees and Shrubs in the Dry Country of Australia, Department of National Development, Canberra.

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References and further reading

McArthur, N.A. (1991) The performance of aluminium building products in bushfires. Fire and Materials 15(3): 117–125. McArthur, N.A. and Lutton, P. (1991) Ignition of exterior building details in bushfires: an experimental study. Fire and Materials 15: 59–64. Pompe, A. and Vines, R.G. (1966) ‘The influence of moisture on the combustion of leaves’, Australian Forest 30: 231–41. Ramsay, G.C., McArthur, N.A. and Dowling, V.P. (1986) Building Survival in Bushfires, Proceedings 4th Australian National Biennial Conference, The Institution of Fire Engineers, Perth, WA 21–24 October 1986. Ramsay, G.C. and Rudolph, L.S. (1988) Buildings and Bushfires – Improving the Chances of Survival. (Videotape, 22 mins), University of Melbourne Ramsay, G.C. and Dawkins, D. (1993) Building in Bushfire-Prone Areas – Information and Advice. CSIRO, Standards Australia Handbook HB36. Ramsay, G.C., McArthur, N.A. and Rudolph, L.S., (1995) ‘Towards an integrated model for designing for building survival in bushfires’. CALM Science Supplement 4: 101–108. Rudolph, L. (1993a) ‘Vegetation and bushfires: Part I – The behaviour of vegetation as applied to the landscaping around buildings in bushfire areas – a review and evaluation’. Landscape Australia 15, 17. Rudolph, L. (1993b) ‘Vegetation and bushfires: Part II – A system for the assessment of the behaviour of vegetation as applied to the landscaping around buildings in bushfire areas’. Landscape Australia 15, 113. Simpfendorfer, K.J. (1984, 1989) Trees, Farms and Fires. Department of Forest, Conservation and Lands, Melbourne. Standards Australia (1991) Australian Standards AS 3959. 1999: Construction of buildings in bushfire-prone areas. Standards Australia, Sydney. Vines, R.G. (1981) ‘Physics and chemistry of rural fires’ in Fire and the Australian Biota. (Eds A.M. Gill, R.H. Groves and I.R. Noble), Australian Academy of Science, Canberra. Webster, J. (1989) The Complete Australian Bushfire Book, Viking O’Neil, Victoria. Wilson, A.A.G. and Ferguson, I.S. (1984) ‘Fight or flee? – A case study of the Mount Macedon bushfire’, Australian Forestry 47 (4): 230–236. Wilson, A.A.G. and Ferguson, I.S. (1986). ‘Predicting the probability of house survival during bushfires’, Journal of Environmental Management, 23: 259–270. In addition to the above references, State Government authorities throughout Australia produce a number of publications in booklet and pamphlet form which are updated over time. These authorities can be contacted for their current materials.

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Index building design, 34–38, 67–71 approach 36–37, 67–68 options 35–36, 72–100 elements 73 methodology 69–71 robustness 37–38, 68–69 building plan 75 building regulations 2, 72 buildings, as refuges 21, 68 ignition of 3–4, 5, 7, 13–21, 70 underground 57, 59 bushfire risk, responses to 4–5 bushfire-resistant plants 23 bushfires, adapting to 3–4 attack period 18–21 causes 8 fuel 10, 27–29, 30,70–71 hazard 2–3 influences on 12 mechanisms of spread 8–9 misconceptions 6–7 modes of attack 21, 29–30 and plant attributes 22–32, 41–42 decks 87–89 design approach 5, 36–37, 39–46, 52, 67–68 design robustness 37–38, 44, 68–69 doors 92–94 earth mounds 58–59 electricity supply 98–99 embers and burning debris 8, 14, 16, 70–71 fences 66 fire front 18–20 flammability of plants 30, 53 flashover 7 floors 5, 85–86 fuel, for bushfires 10–11, 27–29, 30, 70–71 gas supply 99 ground cover 60 gutters 37–38, 83–84 heat radiation 9, 17 hedges 61–64 ignition, of buildings 3–4, 5, 7, 13–21, 70 mechanisms 15–17, 20 kindling 10–11, 13–14, 53, 54 land, suitability and analysis 47–4 sub-division 40–41

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landforms 57–59 landscape design approach 36–37, 39–46, 52 elements 52–66 methodology 45–46 options 22, 47–66 and plant use 41–44 robustness 44 style 49–51 leaf litter see kindling lot size 40 methodology, of building design 69–71 of landscape design 45–46 mulches 60 open spaces 65 outbuildings 95–96 pergolas 87–89 plan shape 75 plant selection 22–23 plants, attributes which affect bushfire attack 22–32, 41–42 bushfire-resistant 23 effects on bushfire attack 30–31 flammability 30, 53 radio 100 refuges 21, 68 robustness of design 37–38, 44, 68–69 roof, cladding 79–82 gutters 37–38, 83–84 profile 76–78 screen planting 61–64 services 71, 97–100 steps and landings 87–89 storage facilities 95–96 telephone 99 television 100 trees and shrubs 53–56 trellis 87–89 underfloor spaces 85–86 vegetation as fuel 10–11, 27–29, 30 vegetation management 42–44 vents 92–94 verandahs 87–89 walls, cladding 90–91 garden 66 water supply 97–98 wind 12, 17, 21, 62–63, 70 windbreaks 61–64 windows 92–94