IN BUILD 141 (pages 36–38), External fire spread on houses set out the external wall fire resistance requirements for houses and small residential buildings. These were as they applied to the New Zealand Building Code Acceptable Solutions for fire safety, C/AS1, 19 December 2013.
Changes to C/AS1
Since then, changes have been made to the Acceptable Solutions for fire safety, issued as amendment 3, 1 July 2014, and amendment 4, effective 1 January 2017.
The most significant change is the requirement for a notional boundary between two buildings on the same site when it is a sleeping risk group, for example, another house or a sleepout.
Other changes are mostly editorial and clarification with one additional figure to explain fire rating on boundaries.
Notional boundary introduced
The boundary between two buildings on separate titles is the relevant boundary and will be marked on title plans.
For buildings on the same section under one title and the same ownership, a notional boundary exists between the two buildings, for instance, between the main house and sleepout. The requirements may apply to each building.
Choose location of notional boundary
The notional boundary can be located to give the best solution. For example, it may be easier or cheaper to provide a fire resistance rating (FRR) on one building than another on the same property. Therefore, the location of the notional boundary can be selected to take advantage of this.
FRR when buildings less than 2 m apart
The requirements for a FRR for buildings on the same title are the same as for buildings across a relevant boundary:
- If the buildings on the same title are 2 m or more apart, no FRR is required.
- If the buildings are less than 2 m apart, one of the buildings will require an FRR of 30/30/30.
- The location of the notional boundary can be selected by the owner but, once selected, cannot change.
Figures 1 and 2 show how this can apply.
Figure 1 Fire resistance ratings for various sleeping risk group buildings on the same title. (Amended 01/03/17)
Figure 2 Fire resistance ratings for three sleeping risk group buildings on the same title.
The distance is measured from the face of the cladding, not the framing line.
Clarification (added 15/3/17)
In this article it says, ‘The most significant change is the requirement for a notional boundary between two buildings on the same site when it is a sleeping risk group, for example, another house or a sleepout.’
The change was to narrow the requirement for a notional boundary between all buildings to only the sleeping risk group.
With this change, the notional boundary does not apply from garages or sheds to a sleeping risk building. In other words, garages or sheds can be at any distance without the need for a fire separation.