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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. Am planning on cladding the external walls of a property in Cedar and have been asked whether it will rate better than 60/60/60.

Sounds as if the external wall is required to be fire-resisting, presumably because of proximity to the boundary or an adjacent building. Western red cedar cladding of normal dimensions would not meet the 60/60/60 requirement. However, it is possible to create a fire-resistant external wall by installing the cladding over the top of moisture-resistant fire-grade plasterboard. Details are shown in a technical manual that is available as a download via this link: http://www.woodsolutions.com.au/Resources/Design-Construction-Guides. Refer to page 31 in Guide no. 4.

Q. Could you please contact me on 03 53343045 to discuss your reference material with building in bush fire prone areas.

Telephone advice is not available through this service, but if you would like to leave a more detailed question we can give you a written reply. If you particularly want to discuss the topic, a telephone advisory service is available from the Australian Forest Products Association (AFPA). Their Help Line number is 1800 007 463.

Q. I'm currently doing some research for some timber cladding to go into a lift lobby in a multi res. project. Our fire engineer has referred us to this quote from the BCA, "For a Class 2, unsprinkled building, along public corridors, materials must be either a Group 1 or 2 material". However, almost all the listed available species are in group 3. I have read on timber.net.au that if the timber veneer is applied to a treated MDF substrate it can qualify them for group 2. Could you please elaborate on this ? If that is true/current, what treatment must the MDF undergo? and are there any test results to support this ?

As far as we are aware all untreated wood products will fall into Material Group 3 when tested in accordance with AS/NZS 3837. However, fire retardant treated MDF is available which complies with Material Group 2 requirements when overlaid with a natural wood veneer. This is explained in more detail in a new manual published by the Timber Veneer Association of Australia (TVAA), available as a free download from www.timberveneer.asn.au or in hard copy on request to the TVAA. Test certificates can be downloaded from the Briggs Veneers website at http://www.briggs.com.au/flameblock.php.

Q. We've used Hyne OS Brace - an oriented strand board product for wall linings. I noticed you have had various timbers tested as required for BCA C1.10a. Have you tested OSB? I have contacted Hyne and as it's a bracing product - not a wall lining per se - they haven't tested it. Any advice would be greatly appreciated!

We do not carry out tests ourselves on timber products, but certainly a number of timbers have been tested for their fire hazard properties. Actually Specification C1.10a no longer exists - Specification C1.10a was incorporated into Specification C1.10 in the 2011 edition of the BCA and requirements for linings are now set out in Specification C1.10. Since OSB is not manufactured in Australia and is not normally used as an exposed lining material it has probably not been tested for compliance with C1.10. If Hyne don't have this information then it's likely it is not available.

Q. Is there such a thing as a fire rated weather board? I'm building a garage on the boundary and I think it has to be fire proof.

There are various different kinds of "fire ratings". Some timbers are deemed to be bushfire-resistant on the basis that they are relatively difficult to ignite, but we assume your local authority is looking for more than this. Perhaps a rating in terms of the wall's Fire Resistance Level (FRL) is required. This would be in the form 60/60/60 where the three numbers refer to structural adequacy/integrity/insulation (or 90/90/90, or some other combination of numbers denoting time in minutes). If you could find out exactly what the local authority is calling for we may be able to advise you further.

Q. Hi I'm an architect in Melbourne. I have a project - 8 levels - where were are wanting to use Ironbark timber as a decorative cladding to the external. It will not form the sealing of the façade - it will be a decorative layer only applied over a fully sealed wall system. I'm having trouble getting any information related to the fire prevention issues in doing this - our fire engineer has never come across this use before - he has requested information specifically to the AS 1530.1 and AS 1530.3 I was wondering if you were able to assist with this? Many thanks,

AS 1530.1 specifies a combustibility test, but as far as we are aware no untreated wood product would pass this test so as to be classified "non-combustible". A number of timbers have been tested to AS 1530.3. Ironbark is not one of them, but would be expected to perform well on account of its density. However, ironbark has been tested to AS/NZS 3837 which showed that it complies with the criteria in AS 3959 for fire retardant treated timber, even without such treatment.

Q. I am design manager for an apartment building but a part of it contains 2 storey apartments so I wanted to utilise some of the detailing contained in your Technical Design Guide 01. My building surveyor not having any knowledge of your publications wants information or certification of independent tests for compliance.

Technical Design Guide 01 was prepared for Wood Solutions by the Timber Development Association (NSW), who arranged the necessary tests. We suggest you contact the TDA on (02) 8424 3700 for copies of the relevant certificates and/or reports.

Q. Could you please tell me if you can recommend a product that is a clear fire retardant timber coating that has been tested in accordance with AS 3959-2009 in relation to making it a fire retardant product to comply with BAL ratings in Australia?

Cyndan claim to have a clear fire retardant suitable for timber in areas up to BAL-29. You can find out more from their website if you paste this link into your browser: http://cyndan.com.au/en/specialty-coatings/38-fire-retardant-liquid-timber-flame-retardant-chemical-protection.html. Note that it has the necessary fire-retardant qualities but has not passed the weathering test specified in AS 3959 and therefore is only suitable for weather-protected surfaces. This includes exterior timber, as long as it is shielded by a 30° roof overhang, verandah or similar. We are not aware of a clear application that is suitable for fully weather-exposed surfaces.

Q. I am looking to assist a sawmill with MSG timber out of Europe. Grades to be MGP10 and or MGP12. Can you advise what the structural requirements are for MSG graded framing (through the MSG machine)? Or where could I find this information?

Reference to a number of Australian Standards will be required. The characteristic values of the MGP grades (defined as "a percentile value of a statistical distribution, estimated with a specified level of confidence"), can be found in Table H3.1 of AS 1720.1-2010 "Timber structures, Part 1: Design methods". The grading process is carried out in accordance with AS/NZS 1748 "Timber - Solid - Stress-graded for structural purposes, Part 1: General requirements" and Part 2: "Qualification of grading method". Production is then monitored according to AS/NZS 4490-2011 "Timber - Solid - Stress-graded for structural purposes - Verification of properties" to make sure the output is achieving the required strength and stiffness levels. Australian Standards can be purchased on line from the SAI Global bookstore.

Q. Just looking at the Timber Framed Construction for Multi Residential Buildings. In particular the details towards the end of the guide. There are quite a few references to solid timber blocking in lieu of carrying a fire rated sheet through (at floors, roof, etc). Is this a DTS solution or would it need to be justified as an alternative solution?

The references to solid blocking in the Multi Residential Building guides are supported by technical manual no. 6 in the Wood Solutions series. The manual is available for free download via this link http://www.woodsolutions.com.au/fwpa/article_downloads/Design_Guide_06_Sacrificial_Joints_2-2_MB.pdf. Since Wood Solutions Design Guide 6 is based on testing by a Registered Testing Authority it satisfies Part A2 of the BCA volume 1.

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Did you know?

About 6% of Australia’s 147 million hectares of native forests are public forests potentially available for timber harvesting. Timber is harvested from about 1% of those public native forests each year.