Fire safety regulations and codes
Fire safety in New Zealand buildings is controlled by the Building Act 2004 which requires that buildings be designed and constructed to provide safety to occupants and fire fighters in the event of a fire, and to prevent fire from spreading to other occupancies.
The Building Act requires that the Building Regulations (known as the Building Code) be met. The Building Code specifies objectives, functional requirements and performance for fire safety. These are mandatory requirements which can be achieved in three different ways:
- An approved Verification Method, or
- The Acceptable Solution published in the Compliance Document for NZBC Clauses C1, C2, C3 and C4 (fire safety), or
- An alternative solution using specific fire engineering design
There is not yet an approved Verification Method for fire design, so most buildings are designed using the Acceptable Solution with alternative solutions used in special cases.
Because the Building Code is a “performance-based code” it does not specify particular materials or construction methods, but concentrates on the required performance. This generally allows timber to be used on a “level playing field” with other materials.
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Fire safety regulations and codes
Approved documents
The compliance document published by the Department of Building and Housing includes the Acceptable Solution C/AS1 which is a prescriptive method of meeting the performance requirements of the Building Code.
The Acceptable Solution specifies fire resistance ratings for walls and floors in buildings, depending on the occupancy, the height of the building and the active fire protection measures installed.
In many cases the required fire resistance is in the range from half an hour to 2 hours, easily achieved with timber construction.
The Acceptable Solution C/AS1 specifies two categories of fire resistance rating that are assigned to parts of the building or structure; the F-rating and S-rating.
The F-rating is intended to provide sufficient protection for the life safety of occupants and fire-fighters by delaying fire spread from floor to floor, or from any floor to protected escape routes, and it depends on the height and use of the building and the other fire protection features installed.
The S-rating may also be required to prevent fire spread to neighbouring property, so it applies to external walls and supporting structure when the building is close to a property boundary and to walls or floors between separate ownerships, in the same building.
It also applies to primary structural elements in high-rise buildings (with escape height above 25 m).
The S-rating depends on the expected fuel load and the size of window openings and the rating period is intended to prevent fire spread or structural collapse for the complete burnout period of the firecell.
For rooms with high fuel load and small windows the S-rating may be much greater than the F-rating.
In addition to fire resistance of structural elements, the Approved Documents specify requirements for the fire properties of surface finishes of walls, floors and ceilings, to control the early spread of fire and the production of smoke in certain buildings.
These requirements become particularly important if exposed wood panelling or other wood based materials (or plastics) are used as finishing materials.