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Building codes & compliance

Like to know what wood to use building a pergola or framing a barn? How about the difference between tung oil and polyurethane as a floor finish? How to revive decking or deal with merbau stains? Or how to meet the building code or bushfire standards? Or ask about the environmental advantages of wood or forest certification?

Q. I just build a house with a builder in Perth, I worked out that the rafters are longer than allowed by AS1684, and the load on the underpurlin struts is well above the max allowed, now I need help from a competent roof carpenter that has a good working knowledge of AS1684 to advise me (at an affordable rate - not $100's/hour as I would expect from a static/civil engineer). Can you suggest somebody in Perth WA? Many thanks Tom Schnepple

We don't have details of carpenters in WA but we suggest that Greg Meachem might be able to help. We understand his fees are moderate and if he's not suitable he could probably suggest someone as he has been in the WA timber industry for many years. You can contact Greg through Linkedin via this link: https://www.linkedin.com/pub/greg-meachem/41/2a0/398.

Q. Are test reports available on timber stair treads re compliance with BCA slip resistance requirements?

According to BCA 2015, which comes into force on 1st May, dry internal domestic stair treads must have a slip resistance of P3 or R10, OR a nosing strip with a slip resistance of P3 when tested in accordance with AS 4586-2013. We don't know of any raw timber that has been tested, but timber treads are rarely left in the raw state, so it's the surface coating that dictates the slip resistance. Non-slip coatings are available, but note that it must be a coating that has been tested to AS 4586, not just one with a general description as a “non-slip coating”. A suitable product would be Intergrain UltraFloor which has a slip resistance rating of R12 according to the Dulux website at http://www.dulux.com.au/specifier/product/intergrain/interior/flooring-/product-detail?product=2036.

Q. Trying to get a Grade 3 (as assessed under C1.10 of the BCA) timber internal lining up to a Grade 2 by use of intumescent clear varnish coatings...can you help? Does the BCA recognise this as a method? Have you got a contact either in timber or coatings world who I can call? Two projects one in QLD and one in NSW.

We don't know of a clear varnish that will lift timber from Material Group 3 to Group 2. Manufacturers of intumescent paints might have a suitable product. You could try contacting Australian companies such as Resene. Another option is to use timber veneer on fire-retardant treated MDF. This combination achieves Material Group 2, and particular species have even achieved Material Group 1.

Q. I need to determine the FRL of some structural timbers for a building permit and am wondering who can do this and certify it for my building surveyor?

The FRL of structural timber can be determined by reference to Australian Standard 1720 "Timber Structures, Part 4: Fire resistance for structural adequacy of timber members". Note that an FRL may have three components, structural adequacy, integrity and insulation. AS 1720.4 caters only for the structural adequacy component of an FRL, which may be the only requirement, depending on the Class of building and the relevant BCA provision. An FRL that only calls for structural adequacy would be in the form 60/-/-, ie. maintenance of structural adequacy for 60 minutes. A consulting engineer can do the necessary work in accordance with AS 1720.4.

Q. I have used Meranti timber door jambs for an external door. Does this timber comply with or satisfy NSW bushfire Bushfire Attack Level (Bal 12.5) and Building Construction AS 3959-2009?

BAL 12.5 is primarily concerned with protection from ember attack, ie. embers accumulating against the building. Consequently, the lower parts of external elements such as door frames are caught up by the regulations. Any part of a door assembly, including the door frame, that is less than 400mm from the ground, or other horizontal surface such as a deck, must be made from one of the seven timbers classed as "bushfire-resisting", or timber with a density of 650 kg/m³ or greater. Light-red meranti would not qualify, and dark-red meranti is of variable density and therefore difficult to assess.

Q. I am looking for information about New Guinea Rosewood, specifically Fire Hazard properties.

New Guinea rosewood has been tested as solid timber wall and ceiling lining in a thickness not less than 9mm, in accordance with the relevant specification of the Building Code of Australia (BCA). Rosewood falls into Material Group 3 with an average specific extinction area less than 250 m²/kg.

Q. I am doing a university project based on the process involved in using reclaimed/recycled wood for structural purposes. Is there an AS (Australian Standard) to follow/certification process? To my knowledge the majority of the certification is done by an educated visual test? There are also load calculations to determine strength loss and moisture content. But how do I actually certify recycled timber? And is it a costly venture/ if so why? So far to my knowledge salvage yards don't do this for you?

The timber industry has put quite a lot of effort into researching the properties of recycled timber so it can be safely re-used. Grading rules are contained in a document titled Interim Industry Standard Recycled Timber - Visually Stress Graded Recycled Timber for Structural Purposes, which is available for download at this address: http://www.woodsolutions.com.au/Articles/Resources/Interim-standard-Recycled-structural-products. Once the grade has been determined, reference can be made to special span tables for recycled timber (hardwood only at this stage), also available on the net. These documents are not Australian Standards, hence the title "Interim Industry Standard". There is nothing to prevent a salvage yard offering graded timber, and one would imagine this would give them a marketing advantage.

Q. Are there Standards that need to be met in the construction and installation of wooden residential ramps?

It depends what the ramp is for, and what type of residential building you are dealing with. If you just want to build a ramp up to your front door the requirements are fairly general. The Building Code of Australia (BCA) has a performance requirement for private houses (Class 1 buildings) stating that ramps must have safe gradients, suitable handrails and landings, and "be suitable for safe passage in relation to the nature, volume and frequency of likely usage". They must also have a slip-resistant walking surface. Ribbed decking laid at 90° to the direction of travel would be considered adequate. However, if the ramp is required to provide access for people with a disability, in Class 2 to Class 9 buildings, the requirements are very specific, as detailed in Australian Standard 1428.1, "Design for access and mobility, Part 1: General requirements for access - New building work".

Q. Found a Multi-residential timber framed construction book on the timber.net.au web site. Is this still valid? Micjhael Ross - Building Certifier Queensland 0414776163

The MRTFC manuals on the timber.net website are actually the 2001 editions. They are out of date in some respects, particularly with regard to acoustic requirements. We would therefore refer you to the multi-residential construction manuals on the Wood Solutions website where they are available as Technical Design Guides #1, #2 and #3 at this location: http://www.woodsolutions.com.au/Articles/Resources/Design-Construction-Guides.

Q. Having trouble finding a fire indices report on Douglas Fir/Oregon to suit Australian standards. Require this to gain certification for a new shop being built. Can you assist please?

The Early Fire Hazard properties of oregon (Douglas fir) are: Ignitability Index 14; Spread of Flame Index 9; Heat Evolved Index 9; and Smoke Developed Index 3. Data sourced from this publication: http://trove.nla.gov.au/work/9920471?selectedversion=NBD1767125.

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Did you know?

In 2008 seventy percent of known old-growth are in nature conservation reserves.