While timber is a combustible material, it can perform well in fire in comparison to other materials when properly specified. Woodform Architectural specially commissioned Wood & Grieve Engineers (WGE) to produce an independent report clarifying the compliance requirements under the Building Code of Australia (BCA) for acceptable timber fire resistance.
Founded in 1961, WGE is a multi-awarded engineering consultancy based in Australia. Its in-depth knowledge of the BCA and fire-engineering expertise has helped numerous architects fulfill their overall design vision while still complying with the BCA.
In their concise report, you will find a basic overview of the following:
- Performance requirements of timber products
- Applicable BCA deemed-to-satisfy provisions
- Alternative solutions relating to wall and ceiling linings, as well as external wall cladding, that meet fire regulations
Here are excerpts from the report:
- Timber products are generally Group 3 or 4 materials, fire retardant timbers are expected to be Group 2 materials. The Group material of specific products needs to be confirmed by compliance testing provided by the manufacturer.
- Following the Lacrosse fire in Melbourne in November 2014, Fire Brigade and governing bodies have adopted a stance not allowing Alternative Solutions relating to the use of combustible material in external building façades. Therefore all combustible external façades in Type A and B buildings have to be constructed in accordance with the Deemed-to-Satisfy Provisions and be attachments to fire rated external walls.
- When wood is exposed to fire or high temperature, the surface of the wood initially ignites and burns rapidly. The burned wood forms a layer of char which acts as a layer of insulation for the solid wood below. The initial burning rate decreases to a slower steady rate which continues throughout fire exposure.
- The char layer does not usually burn because there is insufficient oxygen in the flames at the surface of the char layer for oxidation of the char to occur. The insulating qualities of timber mean that although the temperature at the char layer may be 300°C, the temperature of the inner wood is considerably lower.
- Depending on the thickness of the timber and type of timber used, a fire may cause charring of the outer layer while the inner layer maintains structural stability of the structure.