Your timber knowledge database from Market Timbers
Purchasing timber can be a daunting experience especially with the endless combinations of sizes, grades, classes and species. Coupled with the tonne of timber terms used in the timber industry, finding the right timber to suit your needs can be a very daunting experience. Market Timbers has over 67 years experience with timber and all our staff are more than happy to point you in the right direction. Whether you’re worried about a pair of stilettos indenting the floor or finding the right species of timber to build in your bushfire affected home, our friendly staff at Market Timbers can help you with your requirements.
Technical information is available on the topics listed below. Please click one of the following headings for more information about that related topic. If there is any further information you require regarding anything timber related, please email our office on [email protected] or contact our toll free number on 03 9314 9999.
- Timber Grading
- Natural Features of Timber
- Janka (Hardness) Ratings
- Floor Slip Resistance
- BCA Building Classes
- Fire Ratings
- Limits for Bow, Spring, Twist & Cup
The grades specified in Australian Grading Standard are primarily based on the features and desired aesthetic appearance. Each piece of hardwood product shall be graded on the face, back, edges and ends, as appropriate, in accordance with the requirements of this Standard, sawn or milled to ordered dimensions, and within the tolerances appropriate to the product.
The grading names in Australian Grading Standard are not intend to indicate a ranking of quality. For some applications and species, an increasing proportion of features may make a product more desirable rather than less.
1. Select Grade
Providing a floor where the feature present or natural discolouration will not dominate the appearance of the floor, this timber flooring is classified as select grade. Select grade has the least number of natural features such as gum veins and pin holes.
MARKET TIMBERS provides select grade timber flooring with limited variation in natural characteristics. All our products have been carefully selected and graded, floorboard by floorboard, to ensure that it meets strict quality standards
2. Medium Feature – Standard Grade
Providing a floor that may have significantly more character than a Select Grade floor, it is classified as standard grade. Standard grade has a moderate amount of natural features. To some degree this will depend on the features present in a particular species. In one species gum veins may naturally be prevalent while in another there may be few gum veins but past borer activity may be more prevalent. Therefore, this grade can be expected to have greater character than Select Grade, and contain an increased amount of gum vein, past borer activity, knots and natural discolouration.
MARKET TIMBERS provides meadium feature – standard grade timber flooring with interesting and distinctive variations and markings, to enhance the look of a timber floor and give it a unique character as individual signature.
3. High Feature Grade
High Feature Grade is also known as Rustic Grade. Providing a floor that contains boards with similar features to Medium Feature – Standard Grade but where the length of features such as gum veins may be longer and past borer activity may be more frequent. Again depending on the species, features will vary and in some instances boards meeting high feature grade may only appear moderately featured. It should be note that the difference in appearance between a Select Grade floor and a Medium Feature – Standard Grade can be quite significant whereas the difference in appearance between a Medium Feature – Standard Grade floor and a High Feature Grade floor can be quite small.
MARKET TIMBERS provides high feature grade timber flooring with unique natural features. Although high feature grade has always been considered the cheapest grade, it is now becoming more popular due to the beauty of its natural look. Modern techniques in the finishing of these floors make them aesthetically stunning.
Knots are the remnants of branches that have been captured by the growing trunk of the tree. The size of the knots is defined as the width which is measured between lines parallel to the length of the timber piece with the knot.
Timber is a natural product. It is allowed to have a certain amount of holes on the timber surface. The size of the holes is measured by their length and width when they appear on the surface of the timber.
In timber industry, the term grain means the general direction of wood fibres relative to the length of the timber piece. Grain also refers to the direction, size, arrangement, appearance, or quality of wood fibres. There are straight grains, irregular grains, wavy grains, and etc.
The most common grain variation is the pattern of the growth rings on the surface, which is determined by the ways the timber is cut. The most two common cutting methods include Quarter sawn and Back sawn.
The grains in quarter sawn timber piece are relatively straight, even and parallel running along the board. The grains in back sawn timber piece have mixed direction that can include cathedrals, crowns or swirls along the face of the board.
According to the specifications in AS/NZS 1080.2.1 – 1080.2.3, the measurement of the grain is to determine the slope. General grain slope calculation is the ratio of the height the grain rises and the distance it travels to reach that height.
4. Gum Veins and Gum Pockets
Gum Veins and gum pockets are common characteristics in most hardwoods. They are the build-up of resin or tree sap and can be easily identified by their colour difference on the same timber piece. The centre of gum veins, generally white in color, has very few wood fibres and is soft in texture. As moving towards the edges of the gum veins, the colour becomes darker and the amount of wood fibres increases.
In Australian Grading Standard, the width of the gum vein and gum pocket shall be measured on the surface of the timber and the length shall be measured along the timber piece. The depth shall be measured at 90o to the surface on which it appears.
5. Checks and Splits
Checks and splits of timber refer to the appearance of cracks in wood. As timber dries out over time, checks and splits are likely to appear. There are different types of cracks in timber, including surface check, normal check, internal check and split.
The width of the check is measured on the surface of the timber piece perpendicular to the longitudinal direction of the check. The length of the split and the length of the check are measured parallel to the length of the timber piece.
In Australian Grading Standard, it is considered inappropriate to include internal checks as part of the grading rules since they cannot always be seen by the grader.
6. Want, Wane and Sapwood
The sapwood of a tree is the youngest wood in a tree’s trunk and is located in the outermost rings. All wood that exists in a tree either currently is or was once sapwood until it reaches a certain age. Sapwood is generally in comparison with heartwood that is the older wood that is deeper in the trunk of the tree and close to the center. Sapwood is also called “living wood” because it is the wood that conducts water from the roots underground to the leaves in the branch. Not only does sapwood conduct water throughout the tree, but it is also responsible for storing water and rationing out the stored water during dry spells.
Wane refers to the presence of bark or lack of wood from any cause on the edge or corner of a piece of timber. Want refers to the absence of fiber on the edge of timber. Want, wane and sapwood are measured as the amount of the deficiency of the cross-section of the timber piece.
Reference: AS 2796.2-2006 Timber – Hardwood – Sawn and milled products – Grade description
For more detailed information, please refer to pdf ‘Australian Grading Standard – Timber Hardwood – Market Timbers’. Click here to view the pdf
The hardness of a timber is measured by the Janka hardness test. The first Janka rating results were created in 1922 in units of pressure Pascal (Pa). The test was standardized in 1927, and after that the results were in units of force (F). This test measures the resistance of a sample of wood to denting and wear. It measures the force required to embed an 11.28mm (0.444 in) steel ball to half its depth into wood. So with this rating system, the higher the number the harder the wood. The Janka hardness test is the industry standard for determining the ability of a particular timber species to withstand denting and wear.
Wood hardness is important since one of the key considerations in selecting the species of wood floor your floor should be how much resistance the wood has to scratches and indentations.
While the Janka Hardness Scale only helps to classify woods based upon hardness and density, it can be a good indication of how much wear and tear a particular wood can withstand. The woods in the upper portion of the Janka Scale, such as 12 and higher tend to resist denting more than softer woods with a rating of 6 and under . The Janka rating can also help determine how difficult a particular wood will be to saw or nail.
Harder wood types can be found in the upper portion of the Janka Scale and are generally recommended for high-traffic areas in homes and businesses. Woods that have a high ranking include Iron Bark and Grey Box
Medium density woods are good for most home applications, such as living rooms and dining rooms. Certain woods may not be recommended for high traffic kitchen use. Some common types are Blackbutt , Brush Box, Blue Gum, and Ash.
Wood types on the lower end of the Janka Scale are best for low-traffic areas such as bedrooms and closets. Softer wood types include American Oak, Black Cherry, Teak, Ash, Rose Wood and Chestnut.
Some understanding of the Janka Hardness Scale can help you decide which hardwood flooring will stand up to your particular needs
The natural durability rating of a timber species is a rating of the timber’s natural resistance to attack by wood destroying fungi and wood destroying insects. Due to the natural characters of the sapwood of all timber species which has poor resistance, the timber durability rating applies only to the heartwood of a timber species.
The reason that the sapwood of all species is non-durable is because sapwood has life-supporting starches and sugars and majority of species contain sapwood which is comparatively easily penetrated by preservatives. As a result, for timber exposed to the weather or in ground contact, the sapwood is normally either removed or preservative treated. When sapwood grows into heartwood over time, extractives are formed which are the factors that mainly determines the degree of timber resistance to attacks by wood destroying fungi and insects.
The timber durability rating takes into consideration the testing of stakes and poles embedded in the ground and the professional opinions of historical performance.
The rating can reflect the life expectancy of a timber species, but it is not intended to predict a precise life span since there are variations within a species and there are differences in conditions between sites and applications where the timber species might be used. Even though the durability ratings do not provide an exact life expectancy, the ratings can be used as indices in broad comparisons between species.
There are two factors that affect the durability of timber products. One is the environment the timber is exposed to, and the other is the natural durability characteristic of particular species.
The natural durability of timber species is divided into 4 classes:
Class 1: Timbers of the highest natural durability.
Class 2: Timbers of high natural durability.
Class 3: Timbers of only moderate durability.
Class 4: Timbers of low durability. These timbers have about the same durability as untreated sapwood, which is generally regarded as Class 4, irrespective of species.
In a given site and application, a class 1 species will last longer than a class 2 species and so on. It should be noted that a class 2 species in a less hazardous situation may last longer than a class 1 species in a different but more hazardous situation.
For each of the four classes there is an expected service life range. The above ground ranges are different from the in-ground contact ranges.
Floor slip rating, also known as floor slip resistance, is a measurement of the coefficient of friction (or resistance to slip accidents) of flooring surfaces. The floor slip resistance test can either be conducted in a laboratory (before or after installation) or on floors in site. Slip resistance testing (or floor friction testing) is usually desired by the building’s owner or manager when there has been a report of a slip and fall accident, when there has been a report of a near accident, or (preferably) before the flooring is installed on the property. Flooring is tested using a floor slip resistance tester to discover if there is a high propensity for slip and fall accidents on it, either dry or (most often) when wet with water or lubricated with other contaminants such as kitchen grease, hydraulic oil, etc.
According to the Building Code of Australia (BCA), the slip resistance of timber flooring is generally acceptable when the surface is dry. The slip resistance of timber flooring can be poor if the surface is wax polished. On stair treads, a slip resistant nosing should be used.
The coefficients of friction required in BCA are:
dry surface : > 0.5
wet surface : 0.2 – 0.4
There are different slip resistance tests which are specified in the following standards:
. Wet pendulum test (Appendix A, AS/NZS 4586; AS/NZS 4663)
. Dry floor friction test (Appendix B, AS/NZS 4586; AS/NZS 4663)
. Wet barefoot test (Appendix C, AS/NZS 4586)
. Oil wet ramp test (Appendix D, AS/NZS 4586)
With time, a timber flooring surface will deteriorate and become more slippery. It is recommended to replace or treat the surface again instead of bearing the increasing risk of slipping.
|Class 1||Class 1a||A single dwelling being a detached house, or one or more attached dwellings, each building, separated by a fire-resisting wall, including a row house, terrace, town house or villa unit|
|Class 1b||A boarding house, guest house, hostel or the like w the a total area of all floors not exceeding 300m2 and where not more than 12 reside. and is not located above or below another dwelling or another Class of building other than a private garage.|
|Class 2||A building containing 2 or more sole-occupancy units each being a separate dwelling.|
|Class 3||A residential building, other than a Class 1 or 2 building, which is a common place of long term or transient living for a number of unrelated persons. Example boarding-house, hostel, backpackers accommodation or residential part of a hotel, motel, school or detention centre.|
|Class 4||A dwelling in a building that is Class 5, 6. 7. 8 or 9 if its the only dwelling in the building.|
|Class 5||An office building used for professional or commercial purposes, excluding buildings of Class 6, 7, 8 or 9.|
|Class 6||A shop or other building for the sale of goods by retail or the supply of services direct to the public. Example: café, restaurant, kiosk, hairdressers, showroom or service station.|
|Class 7||Class 7a||A building which is a car park|
|Class 7b||A building which is for storage or display of goods or produce for sale by wholesale.|
|Class 8||A laboratory, or a building in which a handicraft or process for the production, assembling, altering, repairing, packing, finishing or cleaning of goods or produce is carried on for trade, sale or gain.|
|Class 9||Class 9a||A health care building, including those parts of the building set aside as a laboratory.|
|Class 9b||An assembly building, including a trade workshop, laboratory or the like, in a primary or secondary school, but excluding any other parts of the building that are of another class.|
|Class 9c||An aged care facility.|
|Class 10||Class 10a||Non Habitable Building. Private garages, carports, utility sheds etc.|
|Class 10b||Non Habitable Building. Structure being a fence, mast, antenna, retaining or free standing wall, swimming pool etc.|
|Class 10c||Non Habitable Building. A private shelter.|
According to the Building Code of Australia (BCA), Fire Resistance Level (FRL) is the grading period in minutes for three criteria: structural adequacy, integrity and insulation. Structural adequacy is the ability of a structure to maintain its stability and load bearing capacity. Integrity is the ability of a structure to resist the passage of flames and hot gases. Insulation is the ability of a structure to maintain a temperature below specified limits on the surface not exposed to fire.
Fire resistance levels (FRL) are assigned as performance criteria, in minutes, for structural adequacy, integrity and insulation. This important parameter is defined by three numbers, e.g. 30/30/30 for which the:
– First number relates to structural stability, i.e. the time to elapse before collapse;
– Second number is an integrity requirement, i.e. flames must not pass through the component for this number of minutes;
– Third number is an insulation value, i.e. limits heat transfer through the component.
Timber will decompose to provide a layer of Char to insulate from heat when it is exposed to high temperature. The rate of Char composition slows down as the depth of the Char increases due to the increasing insulation. The FRL of timber means that even though the temperature at the Char layer is high, the temperature of the inner wood is considerably low. The area without the Char layer remains at a low temperature and is able to carry more loads.
The Australian Standard AS 1720.4 Timber Structures: Fire-resistance of structural timber members provides a method of calculating a conservative char depth. This method is considerably accurate and compliances with the BCA requirements.
The Notional Charring Rate is given by C = 0.4 + (280/D)2, where C refers to the Notional Charring Rate, in millimeters per minute (mm/min); D refers to the timber density at a moisture content of 12% in kilograms per cubic meter (kg/m3).
Critical Radiant Flux
Critical Radiant Flux (CRF) is another measurements of fire resistance ability of timber flooring required by BCA. The Critical Radiant Flux test measures the radiant energy required to just sustain burning. It is used in Australia, and in some parts of the USA and some parts of Europe to regulate floor coverings.
The test involves the product being held horizontally under the influence of a radiant heat source at one end. It is ignited at that end and the radiant heat flux at the point at which combustion ceases is determined. This is the Critical Radiant Flux. During the test the floor covering is allowed to burn under the influence of the radiant heat source. There is just sufficient air movement in the test chamber to remove the products of combustion into the flue.
Heat Evolved Index
Heat Evolved Index is also one of the BCA requirements. The heat evolved index relates to the amount of heat released by a burning material, and allows, by its linear scale, distinctions to be drawn between materials on the basis of whether or not the amount of heat evolved from them would be sufficient to cause ignition of nearby combustibles. The higher the index, the more likely is the fire involvement of nearby combustible materials.
The ignitability index relates to the time taken for the volatiles from the test specimens, irradiated at increasing intensity, to form an ignitable gas mixture and be ignited by a small flame. The index is zero if ignition does not occur under the maximum impressed radiation of the heat and could be as high as twenty (20) if ignition occurs within 30 seconds of the test commencement.
Material Group Numbers
Materials that do not reach flashover following exposure to 300kW for 600 seconds, after not reaching flashover when exposed to 100kW for 600 seconds.
Materials that do reach flashover after exposure to 300kW for 600 seconds, after not reaching flashover when exposed to 100kW for 600 seconds.
Materials that reach flashover in more than 120 seconds but less than 600 seconds after exposure to 100kW.
Materials that reach flashover in less than 120 seconds after exposure to 100kW.
Bushfire Affected Zones
If you are concerned about which timbers can be used in bushfire affected areas of Australia, please contact Market Timbers for advice.
Reference:Australian Timber Flooring Association
Under AS 2796.1 bow, spring, twist and cup of hardwood products shall be evenly distributed and within the limits given in the tables below. Values for lengths, widths and thicknesses other than those given in the tables shall be obtained by interpolation and extrapolation.
Note: The limits given for bow, spring, twist and cup are the maximum for each product. Tighter limits may be required for applications such as bargeboards, fascia, joinery, hand rails and similar products.
ADDITIONAL FIRE INFORMATION
- Fire Hazard Properties – info and definitions (non single dwelling)
- Fire Hazard Properties – CRF
- Fire Hazard Properties – Wall and Ceiling Linings/Coverings
- Timber Spread-of-Flame & Smoke-Developement Indexes
- Bushfire Affected Zones – Bushfire Attack Level (BAL)
The Building Code of Australia (BCA) regulates materials that are used in construction of Class 2 to 9 buildings (not single family homes). These are stipulated by “Specification C1.10”.
In addition, the BCA regulates materials that are used for floor, wall and ceiling coverings separately in Class 2 to 9 buildings (not single family homes). These are stipulated by “Specification C1.10a”.
The term that is used is Fire Hazard Properties and the reference clause in the BCA is “C1.10 Fire Hazard Properties”.
The BCA requires any material or assembly used for flooring, floor covering and wall and ceiling lining materials to comply with Specification C1.10a. All other materials (i.e. whatever holds up the floor covering or lining) are required to comply with Specification C1.10.
Some products may require different specifications depending on use. An example of this is plywood flooring used on joists and bearers. The plywood is required to comply with Specification C1.10a when the plywood is the topmost layer, i.e. exposed plywood flooring. When it has a carpet, decorative timber or tiles etc over it, then the plywood is required to comply with Specification C1.10. The topmost layer of carpet or other floor covering is required to comply with Specification C1.10a as it is the covering.
Similarly for walls, a lining such as timber linings or panels are required to comply with Specification C1.10a. The studs that are used to support the linings are required to comply with Specification C1.10.
BCA Specification C1.10a requires floor materials and floor coverings to comply with the required critical radiant flux (CRF) and wall and ceiling linings to have the required material group number.
Critical radiant flux (CRF) – means the critical heat flux at extinguishment as determined by AS ISO 9239.1
Material Group Number – means a number assigned to materials when exposed to different levels of irradiation for different periods of time when determined in accordance with AS ISO 9705 or AS/ NZS 3837
Specification C1.10 – covers materials used in the assembly / construction of flooring (eg: plywood, birch, eucalypt base or subfloor)
Specification C1.10a – covers floor coverings which is the timber exposed at the top.
Building class 2 – 9 Properties of Floor materials and Floor coverings
Specification C1.10a of the BCA 2007 states that a floor material or floor covering’s Critical Radiant Flux (CRF) cannot be less than the value stated in the table below for each building class. Values are stated in kw/m².
Note: Buildings without sprinkler systems cannot have a smoke development rate greater than 750 %-minutes.
|CRITICAL RADIANT FLUX (CRF KW/M2) OF FLOOR MATERIALS AND FLOOR COVERINGS|
|Class of building General||General|
|Without Sprinkler System||With Sprinkler System||Fire- Isolated Exits|
|Class 2, 3, 5, 6, 7, 8 or 9b excluding accommodation for the aged||2.2 kw/m²||1.2 kw/m²||2.2 kw/m²|
|Class 3 Accommodation for the aged||4.5 kw/m²||2.2 kw/m²||4.5 kw/m²|
|Class 9a Patient care areas||4.5 kw/m²||2.2 kw/m²||4.5 kw/m²|
|Class 9a Areas other than patient care areas||2.2 kw/m²||1.2 kw/m²||4.5 kw/m²|
|Class 9c Resident use areas||–||2.2 kw/m²||4.5 kw/m²|
|Class 9c Areas other than resident use||–||1.2 kw/m²||4.5 kw/m²|
The tables below sort species when in 19 mm thick or greater T&G flooring
|SPECIES WITH A CRITICAL RADIANT FLUX (CRF) OF 4.5 KW/M2 OR GREATER|
|Beech, myrtle||Gum, red, river||Karri|
|Blackbutt, New England||Gum, spotted||Mahogany, red|
|Bloodwood, red||Gum, yellow||Pine, white cypress|
|Box, brush||Ironbark, grey||Tallowwood|
|Box, grey||Ironbark, red||Turpentine|
|Gum, blue, Southern||Jarrah||Wattle, silver|
|SPECIES WITH A CRITICAL RADIANT FLUX (CRF) MORE THAN 2.2 AND LESS THAN 4.5 KW/M2|
|Ash, alpine||Gum, blue, Sydney||Pine, celerytop|
|Ash, mountain||Gum, Manna||Pine, radiata|
|Ash, silvertop||Gum, rose||Stringybark, brown|
For 12 mm thick T&G flooring, all species listed in tables above have a CRF of more than 2.2 and less than 4.5kW/m2, where they are backed by particleboard or laid on a non-combustible substrate such as concrete. All species in tables above have a smoke development rate less than 750%-min.
Wall and ceiling linings are required to meet different prerequisites for different building types, location within the building and whether it is sprinkled or not.
Material used for wall and ceiling linings is required to have a Group Number of 1, 2 or 3 and buildings not fitted with sprinklers are required to have a smoke development rate not more than 100, or an average extinction area less than 250m 2/kg.
Group 3 materials refer to timber products,
Group 2 materials are predominately fire retardant timber and
Group 1 materials are non-combustible or near non-combustible.
|SPECIES TESTED WITH A MATERIAL GROUP NUMBER 3|
|Ash, alpine||Gum, blue, Sydney||Mahogany, red|
|Ash, mountain||Gum, blue, Southern||Marri|
|Ash, silvertop||Gum, Manna||Merbau|
|Beech, myrtle||Gum, red river||Messmate|
|Blackbutt||Gum, rose||Pine, radiata|
|Blackbutt, New England||Gum, shining||Pine, cypress, white|
|Blackbutt WA||Gum, spotted||Sheoak|
|Blackwood||Gum, sugar||Stringybark, yellow|
|Bloodwood, red||Gum, yellow||Tallowwood|
|Box, brush||Ironbark, grey||Turpentine|
|Box, grey||Ironbark, red Wattle, silver||Box, grey, coast|
All these species have a maximum Average Extinction Area less than 250m2/kg. Also, with the exception of Blackbutt WA, which was nominally 12mm thick, all the species tested were nominally 19 mm thick, tongued and grooved and with a dressed surface.
Veneered panels that have a veneer density greater than 500kg/ m3 and are on MDF or particleboard 12 mm thick or greater, have a Group No 3 and an Average Extinction Area of less than 250 m2 / kg. This covers most timber veneers, but specific test data may be available for some selected low density veneers.
Building Class Types where GROUP 3 MATERIALS allowed (meeting BCA standards)
|Class of building||Fire-isolated exits||Public corridors||Specific areas||Other areas|
|Class 2 or 3 – excluding accommodation for the aged, people with disabilities and children|
|Unsprinklered||1||1, 2||1, 2||1, 2, 3||1, 2, 3||1, 2, 3|
|Sprinklered||1||1, 2, 3||1, 2, 3||1, 2, 3||1, 2, 3||1, 2, 3|
|Class 3 or 9a – accommodation for the aged, people with disabilities and children|
|Unsprinklered||1||1||1||1, 2||1, 2||1, 2, 3|
|Sprinklered||1||1, 2||1, 2||1, 2, 3||1, 2, 3||1, 2, 3|
|Class 5, 6, 7, 8 and 9b schools|
|Unsprinklered||1||1, 2||1, 2||1, 2, 3||1, 2||1, 2, 3|
|Sprinklered||1||1, 2, 3||1, 2, 3||1, 2, 3||1, 2, 3||1, 2, 3|
|Class 9b other than schools|
|Unsprinklered||1||1||1||1, 2||1, 2||1, 2, 3|
|Sprinklered||1||1, 2||1, 2||1, 2, 3||1, 2, 3||1, 2, 3|
|Sprinklered||1||1, 2||1, 2||1, 2, 3||1, 2, 3||1, 2, 3|
|Common Name||Spread-of-Flame Index (0-10)||Smoke-Developed Index (0-10)|
|Blackbutt, New England||7||3|
|Cedar, Red, Australian||8||3|
|Cedar, Red, Western||10||4|
|Fir, Douglas (Oregon)||9||3|
|Gum, Blue, Sydney||7||3|
|Gum, Grey, Mountain||5||3|
|Gum, Red, River||6||3|
|Gum, Rose (plywood)||8||3|
|Gum, Spotted (plywood)||8||3|
|Pine, Hoop (plywood)||9||3|
|Pine, Slash (plywood)||8||3|
Note: Nominal thickness of samples tested: red baltic 21.5 mm; white baltic 44mm; plywoods 12mm; mountain grey gum 15 mm; silvertop ash, New England blackbutt, red bloodwood, grey box, brownbarrel, Sydney blue gum, river red gum, rose gum, shining gum, grey ironbark, red ironbark, karri, kwila, slash pine silvertop stringybark, yellow stringybark and turpentine 19mm.
In the Australian Standards As 3959, they have classified different bushfire intensity levels that a home may experience during a bushfire. These are referred to as Bushfire Attack Levels, or BAL’s for short.
There are 6 bushfire attack levels in total, these are:
- BAL Flame Zone – The risk is considered to be EXTREME
There is an extremely high risk of ember attack and burning debris ignited by windborne embers, and a likelihood of exposure to an extreme level of radiant heat and direct exposure to flames from the fire front.
The construction elements are expected to be exposed to a heat flux greater than 40 kW/m²
- BAL 40 – The risk is considered to be VERY HIGH
There is a much increased risk of ember attack and burning debris ignited by windborne embers, a likelihood of exposure to a high level of radiant heat and some likelihood of direct exposure to flames from the fire front.
The construction elements are expected to be exposed to a heat flux not greater than 40 kW/m²
- BAL 29 – The risk is considered to be HIGH
There is an increased risk of ember attack and burning debris ignited by windborne embers and a likelihood of exposure to an increased level of radiant heat.
The construction elements are expected to be exposed to a heat flux not greater than 29 kW/m²
- BAL 19 – The risk is considered to be MODERATE
There is a risk of ember attack and burning debris ignited by wind borne embers an a likelihood of exposure to radiant heat.
The construction elements are expected to be exposed to a heat flux not greater than 19 kW/m²
- BAL 12.5 – The risk is considered to be LOW
There is a risk of ember attack.
The construction elements are expected to be exposed to a heat flux not greater than 12.5 kW/m²
- BAL Low – The risk is considered to be VERY LOW
- There is insufficient risk to warrant any specific construction requirements but there is still some risk.
These individual levels are based on:
- The region where you live.
- The vegetation type around your property.
- The distance from your home to individual vegetation types.
- Slope on the property.
Once you have worked out your bushfire attack level, you are then able to refer to the relevant section of the Australian Standards AS 3959. These sections guide you on the steps that should be taken during the construction or retrofitting of your home, this will lower the risk associated with living in a bushfire prone area.