At 650kg m3, Australian Oak (ASH’s brand of Tasmanian Oak) is an inherently bushfire resistant hardwood – naturally rated at Bush Fire Attack Level 19 (BAL-19). This means that Australian Oak, and our uniquely externally durable IronAsh treated Tasmanian Oak, can be used in areas of BAL-19 or lower (12.5 and LOW).
While this is widely accepted for the window and door market, the waters become a little muddy when we talk cladding, decking and screens. Let us explain.
The table below is taken from WoodSolutions Design Guide #4 – Building with Timber in Bushfire-Prone Areas. This document is available for download on the WoodSolutions Technical Design Guide page. You will need to sign in (which is free).
BAL-19 materials begin at page 15 and explain that ‘Windows, Shutters and Screens’ above 400mm from the ground can be any ‘timber as usual’ while ‘Windows, Shutters and Screens’ starting from within 400mm of the ground must be manufactured using at least BAL-19 or higher materials. This is the sweet spot for Australian Oak because most species with a higher BAL rating are harder, less stable, expensive and less predictable according to window manufacturers.
What is even more interesting is that the table then details cladding and screen requirements – listed as ‘External walls, lightweight cladding’. The cladding or screening in a BAL-19 area must, in fact, be of a higher resistance to bushfire attack unless situated 400mm or above the ground. At which case the table states that we can use all ‘timber products as usual’.
So, IronAsh cladding and screening can be used in BAL‒LOW, BAL‒12.5 and BAL‒19 provided it is not installed within 400mm from the ground. Therefore consider elevating your building 400mm or using a deemed bushfire resistant product such as fibre-cement or corrugated metal sheeting or stone to compliment your stunning purchase of IronAsh cladding.
Refer to WoodSolutions Technical Design Guide 4 – ‘Building with Timber in Bushfire-Prone Areas’ for more.
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