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I am currently writing our waste management procedure, and would like to know if there is any treated timber that does not come under the classification of "Timber that has been treated with preservatives" under "Schedule 2 Materials that must not be burnt so as to discharge visible smoke into the environment" in the Environmental Protection (Unauthorised Discharges) Regulations 2004. We are looking at what off-cuts of timber can be burned as energy recovery as part of our waste minimisation programme. Many thanks

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The answer to your question turns on what the regulations mean by ‘preservatives’ and what they aim to achieve. There doesn’t appear to be a definition of a ‘preservative’ in the regulations, so a strict interpretation might prohibit the burning of any treated timber. On the other hand the aim of the regulations seems to be to prevent visible smoke in the environment, which suggests that if treated timber can be burned without discharging visible smoke into the environment, then that would be acceptable. It’s not recommended to burn timber treated with arsenic-based preservatives unless it’s done under controlled conditions, because arsenic is given off in the smoke and left behind in the ash. However, the regulations don’t seem concerned with this potential problem. But timber treated with creosote would clearly be prohibited since it gives off a black oily smoke. Then again ‘Blue Pine’ (house framing treated against insect attack) is only treated with a low-level chemical such as permethrin, as used in Mortein, which would not leave a dangerous residue nor produce any more smoke than untreated timber. We feel you really need to get a ruling from the WA Environmental Protection Authority, taking into account the kind of treated timber you propose to burn.

treated timber, burning, waste disposal, waste management, smoke, emissions

Hi, the DA Conditions for my house require compliance with AS3959-2009 level 12.5(BAL). Is there a way of chemically treating my bifold doors and front door (meranti) to make them compliant instead of changing the type of wood from which they are constructed?

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AS3959-2009 allows the application of fire retardant coatings as a means of making timber "bushfire resistant", up to a Bushfire Attack Level (BAL) of 29. Fire retardant coatings have to meet the test criteria described in the Standard, so any product marketed for this purpose should come with a certificate from a recognised testing authority. The Standard also recognises timbers with a density greater than 650 kg/m³ as being suitable for window joinery and door frames in areas up to BAL 19. Meranti is divided into two groups, light red and dark red. Light red meranti is not dense enough, but dark red meranti would meet the density requirement, and therefore would meet the fire resistance rating, with no special treatment or coatings. This assumes you have a solid core front door. If you have a hollow-core front door, or your door is made from light red meranti, another way to comply is to fit a non-combustible kickplate on the outside for the first 400 mm above the threshold. We asume your bifold doors are glazed doors. If the glazing is more than 400 mm above the adjacent external surface, there are no special bushfire requirements for the glass. If the glazing is less than 400 mm from the ground, deck or other adjacent surface, the Standard calls for "Grade A safety glass minimum 4 mm".

For more information about the design, construction and maintenance of timber in bushfire-prone areas, download the free WoodSolutions guide – Building with timber in bushfire-prone areas.

bushfire safety

Hi Wanting to build a small plywood box beam industrial shed, approx ~16-20m x ~40m clear span, N3 wind zone (NSW). I am looking for engineer with plywood box-beam experience?

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The NSW Division of the Institution of Engineers Australia may be able to give you the names of some firms with experience in the design of plywood box beams. Failing that, the staff at Timberbuilt are highly experienced in all aspects of structural timber design. You can visit their website at www.timberbuilt.com.au.

For more information about the design, construction and maintenance of plywood box beams, download the free WoodSolutions guide – Plywood box beam construction for detached housing.

Standards Beam Plywood

Referring to Australian National Timber Dev. Council's web site, we noted that merbau is defined by AS-3959-2009 as bushfire-resisting timber. Could you please advise us is it classified as non-combustible material? Equivalent to BS 476?

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Merbau is classified as a bushfire-resisting timber in Australia because it has fire characteristics similar to timber treated with a fire retardant. This doesn't mean it won't burn, just that the heat released when it does burn is within the limits specified in Australian Standard 3959-2009.

British Standard 476 has a number of parts. The part dealing with non-combustibility is Part 4 which specifies a test to differentiate between non-flammable materials, such as plaster-based wall linings, and materials which undergo flaming combustion, such as wood products. It is most unlikely that any wood product would achieve classification as a non-combustible material as defined in BS 476: Part 4. Of course, "non-combustible" materials may still have undesirable fire qualities in that they may melt, shrink, collapse or change their nature in some other way. However, by definition they will not contribute to the fire load.

For more information about the design, construction and maintenance of timber in bushfire-prone areas, download the free WoodSolutions guide – Building with timber in bushfire-prone areas.

AS-3959-2009, British Standard 476, BS 476, merbau, bushfire-resisting, bushfire, BAL

I'm rebuilding at Kinglake in Victoria, and have ordered windows. My building surveyor said that Jarrah windows are dense enough to be classed as bushfire resistant. I need to comply with BAL29 and noticed that Jarrah is not one of the 7 approved woods. What would you recommend?

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Australian Standard 3959-2009, Construction of buildings in bushfire-prone areas, allows any type of timber to be used for windows in areas rated Bushfire Attack Level (BAL) 29, if bushfire shutters are fitted. If shutters are not fitted, timber window frames and window joinery must be made from "bushfire-resisting timber" as defined in Appendix F of the Standard.

Timber is considered to be "bushfire-resisting" if the material itself passes the specified fire test, or if it is impregnated with fire-retardant chemicals, or if it is coated with a fire-retardant. Timber impregnated or coated with fire-retardant must pass a weathering test as well as the fire test.

As you say, jarrah is not one of the seven types of timber that are deemed to be "bushfire-resisting" on the basis of their material properties. Jarrah is most unlikely to be able to be impregnated with fire-retardant chemicals because of its density. It might be possible to find a fire-retardant coating that has passed both the weathering test and the fire test specified in the Australian Standard, but failing that, in our opinion jarrah could not be classified as "bushfire-resistant" as defined in the Australian Standard. We suggest you discuss this further with your building surveyor.

For more information about the design, construction and maintenance of timber in bushfire-prone areas, download the free WoodSolutions guide Building with timber in bushfire-prone areas.

Bushfire shutters, Bushfire prone areas, Bushfire resisting timber, AS3959, BAL, windows, Jarrah

Building on bushfire-prone land, DA approval requires compliance with AS 3659-1999 re type of timber. Which of the permitted species are best for decking, deck joists, cladding and window awnings? Also, will 'Firetard 120' comply to treat cedar windows?

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The Standard number is actually AS 3959 and it seems your building has been approved under the 1999 edition, rather than the latest (2009) edition. 

All the species considered equivalent to fire retardant treated timber under AS 3959-1999 fall into Durability Class 1 or 2 above ground, and therefore all are suitable for deck joists and bearers.

For the decking we suggest kwila (merbau) or ironbark. For the cladding, it is a question of which species are available kiln-dried and in a suitable profile, since all have the required durability. Silvertop ash would perhaps be the least desirable for cladding, since it commonly contains numerous gum veins.

Regarding the use of 'Firetard 120' as a means of making cedar windows compliant, we were not sure whether this was applied by pressure impregnation or as a brush-on process. The Standard requires fire retardant treatments to pass an accelerated weathering test unless the treated component is shielded from the weather. So if any of the windows are exposed to the weather it will be necessary to obtain a certificate from the manufacturer or supplier to show that the product (a) has the required fire retardant properties, and (b) passes the accelerated weathering test. If the product has not been tested, then the window joinery can be made from a suitable hardwood, eg. kwila.

For more information about the design, construction and maintenance of timber in bushfire-prone areas, download the free WoodSolutions guide Building with timber in bushfire-prone areas.

BAL, AS3959, BAL29, Decking, Cladding, Window awnings, Cedar, Bushfire-prone land, Fire retardant timber, Kwila, Ironbark

We have used your report on particle board to give to our building surveyor to satisfy the BCA for lining material but need to know the smoke growth rate index. Do you have that data on hand?

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A Smoke Developed Index of 3 on a scale of 0-10 is quoted for standard particleboard in a publication of the Engineered Wood Products Association of Australasia (EWPAA), available for download here

For more information about alternative solution fire compliance in internal linings, download the free WoodSolutions guide here.

particle board, fire, smoke developed index, smoke growth rate

I'm trying to find the lightest wood that will comply with Section C 1.10 - for a Class 6 building without a sprinkler system. Our certifier has advised that Silver Top Ash will comply for smoke development and spread of flame index - can you please advise the lightest timber that would comply or a few options as we are restricted by weight on the ceiling.

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To comply with Specification C1.10 of the BCA, our understanding is that wall and ceiling linings in Class 6 buildings must have an average specific extinction area less than 250 m²/kg and fall into the Material Group required for each part of the building. Timber that is not treated with a fire retardant generally falls into Material Group 3. This is satisfactory for some parts of an unsprinklered Class 6 building but not all parts. For example, wall and ceiling linings in fire-isolated exits must fall into Material Group 1, while in public corridors Material Group 2 is required. If your certifier can advise which Material Group is needed for the area under consideration we can look into it further.

For more information about alternative solution fire compliance in internal linings, download the free WoodSolutions guide Alternative Solution Fire Compliance, Internal Linings.

BCA, fire, fire compliance, C1.10, ceiling

I am drawing up a fire rated detail for a class 5 building I am documenting. If you can please send me an email address I can forward that detail to you so you can take a look at it. Basically there is a 190 core filled reinforced block wall with a 90x35 top plate and above that I have drawn 2x45 timber blocking between roof truss. If you can send me a contact email I will send the detail through for you to look over.

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Our service doesn’t extend to approving or disapproving specific construction details – instead we try to provide designers with the tools to do that themselves. Along the way we can give general advice on the properties of timber and suggest how it would perform in a given situation. In this case you might find it helpful to refer to our Technical Design Guide #03 titled “Timber-framed Construction for Commercial Buildings Class 5, 6, 9a & 9b”. The Guide can be downloaded here. It sounds as if you are wanting to make use of the fire resistant properties of timber when exposed to fire. If so, section 3.4 of the Guide explains how to calculate fire resistance taking into account the charring rate of the particular timber species.

For more information about fire precautions during construction of large buildings, download the free WoodSolutions guide – Fire Precautions During Construction of Large Buildings.

fire details, class 5, fire rating

I am looking for information regarding the Australian Standards for Timber Flooring specifically for bowing or bending tolerances. I was hoping you could help me or maybe even point me to the right direction as to where I can find this information.

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There are two sets of Standards for timber flooring, one for softwoods and one for hardwoods. Tolerances for bow, spring, twist and cup are set out in Australian Standard 4785.1 for softwoods and Australian Standard 2796.1 for hardwoods, although in fact the same tolerances apply in both cases. The Standards also include tolerances on tongue and groove dimensions.

For more information about the design, construction and maintenance of timber flooring, download the free WoodSolutions guide Timber flooring – design guide for installation.

flooring, standards, spring, twist, cup

I am documenting some homes in a BAL 12.5 bushfire zone. We were interested in using Pacific teak, but have realised that it is classed as an eco timber, sourced from the Solomon Islands. Are you aware of any suppliers of Pacific teak who have had ATIC certification?

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Some teak production has achieved certification by the Forest Stewardship Council (FSC) but we are not sure that "Pacific teak" is actually teak. Some importers are applying the name "Pacific teak" or "New Guinea teak" to a timber more commonly known as vitex (botanical name: Vitex cofassus). This is a major commercial species of the Solomon Islands, so is probably what you are sourcing. Vitex is available certified under several different schemes, you can find our more if you enter "vitex timber certification" in your browser.

For more information about the design, construction and maintenance of timber in bushfire-prone areas, download the free WoodSolutions guide Building with timber in bushfire-prone areas.

Pacific teak, vitex, certification, ATIC

I have a client that is wanting to use meranti externally as door frames on his house, I have told him it is not durable enough for external use and doesn't meet the standard for external use. I can't seem to find any documentation that states that class 4 timber is not allowed for external use, can you advise me where I might get this to provide him with the documentation. We are based in New South Wales.

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Meranti would be suitable for external door frames if the doors were set back under a verandah or canopy, but in our view it's not the best choice for full weather exposure unless preservative treated by the LOSP process. Some joinery manufacturers treat their meranti window frames in this way.

However, as far as we are aware there's no regulation that says untreated Class 4 timber is not allowed for external door frames.

The Building Code of Australia (BCA) is mainly concerned with structural materials and doesn't cover door frames.

Perhaps reference to Australian Standard 5604 "Timber - Natural durability ratings" might persuade your client. AS 5604 quotes a "probable life expectancy" for Class 4 timbers of up to 7 years in above-ground situations fully exposed to the weather.

For more information about the design, construction and maintenance of timber windows and doors, download the free WoodSolutions guide Timber windows and doors.

meranti, durability, door frame, AS 5604, Class 4

We are building a light-weight Class 3 building and have fire rated walls. Where we have connections between a fire rated wall and a non-fire rated wall/roof/floor, we are wanting to use connection details noted in the Wood Solutions Guide using 45mm solid timber blocking. The details we are wanting to use are figures 39, 49 and 54 of the Wood Solutions Guide 02. The certifier has asked us if Wood Solutions has any test certificates of this system and if the 45mm blocking can be pine?

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The use of sacrificial timber construction joints as shown in Wood Solutions Guide 02 is in accordance with the requirements of the BCA Volume 1 Provision C3.16 Construction joints.  The compliant timber details are described in Wood Solutions Guide 06 Timber-framed Construction – Sacrificial Timber Construction Joint  – Exova Warringtonfire Australia having undertaken the testing. And pine blocking is OK (or any timber with a density not less than 450kg/m³). We can provide a letter from Exova Warringtonfire which should serve the purpose of certification.

Read more about this topic in the WoodSolutions Technical Design Guide 2 MRTFC and Guide 06 Timber-framed Construction

For more information about alternative solution fire compliance in internal linings, download the free WoodSolutions guide – Alternative Solution Fire Compliance, Internal Linings.

Class 3 building, fire rated walls, timber blocking, fire engineering, mrtfc, Sacrificial Timber Construction Joint

We have a project in which a fire wall has been built incorrectly in roof trusses, on top of a block wall. Can the builder build a solid timber wall from 100 to 1.100mm at peak "top of ridge" about 5meters long, wall out of 45mm solid timber = 1 hour to burn through?

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Your solutions sounds workable, on the same basis that timber is accepted as “sacrificial” in party wall construction. Applying formula 2.1 in Australian Standard 1720 Part 4: Fire resistance for structural adequacy of timber members, pine is predicted to char to a depth of 40mm after 60 mins exposure to fire, assuming a wood density of 550 kg/m³, so 45mm pine would be sufficient. Any gaps or construction joints would need to be caulked with fire grade sealant, but otherwise it seems a satisfactory solution.

For more information about the design of sacrificial timber blocks, download the free WoodSolutions guide – Timber-framed Construction – sacrificial timber construction.

Australian Standard 1720 Part 4: Fire resistance for structural adequacy of timber members, char rate, fire grade sealant

I have been asked some questions about a bracing wall table 8.18 type H method B. (ply) fixings at each end of the bracing panel need to be 13 kn minimum. My problem is every connection into the concrete that I research has data relating to 32 mpa concrete (housing generally uses 20 mpa) or specifies a 140 mm slab - again not common internally in housing. I'm just wondering if there are any recommendations for what fixing to use as I must be missing something here.

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Mitek’s Titen HD Anchor THD10100 is rated for 20 MPa concrete and only needs a 65mm or 75mm hole, depending whether it’s a 35mm or 45mm bottom plate. A single stud anchor won’t give you the rating you need, but uplift capacity can be doubled by installing two stud anchors. For technical info write StudAnchor-MiTek in your browser.

For more information about timber in internal design, download the free WoodSolutions guide – Timber in Internal Design.

bracing wall, bracing panels, shear wall, fixings, anchors

Does a door opening in a non-load bearing wall requires a double jamb stud. Wall span is 2200mm and the door is 970mm wide centrally located. Is there a standard provision on this for a non-load bearing wall?

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That’s a fairly wide door – standard interior door widths are usually between 620mm and 820mm. Australian Standard 1684 advises that jamb studs at the sides of doorway openings up to 900mm may be the same size as the common studs, providing jamb linings or other comparable stiffeners are provided. For a doorway opening of 970mm you might want to use 2/90 x 35 studs to ensure sufficient stiffness so the door can shut (or accidentally slam) without shaking the wall.

For more information about the design, construction and maintenance of timber windows and doors, download the free WoodSolutions guide Timber windows and doors.

door studs, door jamb, wide door, AS1684, double studs

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