Issue 48 – April 2013
In general, garage walls within 1 m of the boundary require a 30/30/30 fire rating. That is a wall system that has been tested or assessed to provide a minimum of 30/30/30 fire rating by a recognised authority. There is no specific requirement within the new New Zealand Building Code clause C Protection from Fire Acceptable Solution for either risk of roof collapse or direction of wall collapse as stated in paragraph 4.4.1 of Bulletin 557 Timber-framed garages. Also B1/VM1 paragraph 2.2.4 modifies clause 4.2.4 of AS/NZS 1170 Structural design actions or specific design by stating that 'after a fire a wall must be designed to withstand the most critical of the two situations listed in b(ii) and b(iii) – typically this is b(iii), a uniformly distributed horizontal face load of 0.5 kPa in any direction.
Summarised from BRANZ Guideline, March 2013.