Using fire retardant timbers and treatments

Posted: September 20, 2010 by DIY Big Boss in Timber Decking / Cladding / Fencing, Timber Structural / Construction / Other
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Photo from timber for bush fire prone areas report (click on image for link). Photo by Paul Harr (architect) extracted from report

If you live in a part of Australia that is subject to the threat of bush fires, then using timber that resists fire is of extreme importance.  So today we thought we would explore which timbers are best for this purpose.

Basically all houses that are built in bushfire areas (as determined by the applicable State Government) are subject to Australian Standard AS3959 and covers “the most effective means for addressing the threat to houses” as a result of fire and related heat, sparks etc.  Houses are then categorised as to their level of risk.  If you live in such an area it is wise to pick up a copy.

Now it is necessary to silence the rumblings which suggest that having a deck in a bush fire prone is the most likely thing to cause the property to be vulnerable to a bushfire.  It is not true, the single biggest danger actually comes from a failure to adequately clear vegetation from around the home.  All homes in such areas should have a moat of non vegetated land.  If you have a deck then your land moat should extend around it.

This information is backed up by a report by Warrington Fire Research Australia, which confirms the CSIRO’s earlier findings that even where houses are made of wood or have external wooden features like a deck, that the destruction was not caused by the timber igniting, but rather from ember entry into the house.  The summary is that houses tend to burn from the inside to the out, using household furnishings as their main fuel.

All that said, there are still ways to ensure that the timbers you use are the best for your area.  There are seven high-density native hardwood timbers which have significant natural fire resistance.  These timbers are classified as fire retarding by the AS3959 so can be used without treatment in bush fire areas:

  • Blackbutt
  • Kwila (Merbau)
  • Red Iron Bark
  • Red River Gum
  • Sivertop Ash
  • Spotted Gum
  • Turpentine

These timbers are fairly readily available and you can find them also in the DIY Bargain Bin Timber Decking, Cladding and Fencing Section along with in the DIY Bargain Bin Timber Structural, Construction and Other section.

Blackbutt wood from Timeless WA Hardwoods

If you have already built your deck and are in a bush fire prone area to a category 3 level you can use a product called Firetard120, which is a fire retardant for timber.  It has been tested by the CSIRO and approved up to this level.  Using an alternative treatment like this can be a less expensive option for some, and also allows a wider range of timbers to be used.  For example if you have your heart set on a particular type of timber, treating it with this product, which dries clear, will assist in making your timber fire resistant.

Of course you do not have to be in a fire prone area to want to treat your external timber decks and other structure.  That is why such products are great.

For more information, about Building with timber in fire prone areas and use of Fire Resistant Technology, click on these two links.


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