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External wall requirements for Class 1 buildings

The information here relates to external wall construction requirements for residential Class 1 and 10 buildings if they are required to be fire resisting. The requirements are set out in Part 3.7 of the National Construction Code (NCC) Volume Two – Housing Provisions.

External walls of Class 1 Buildings 

The National Construction Code (NCC) sets out that an external wall of a Class 1 building, and any openings in that wall, must comply with Clause, if the wall is less than: 

  • 900mm from an allotment boundary other than the boundary adjoining a road alignment or other public space, or 
  • 1.8m from another building on the same allotment other than an appurtenant Class 10 building or a detached part of the same Class 1 building. 

The distance from any point on an external wall of a building to an allotment boundary or another building is the distance to that point measured along a line at right angles from the allotment boundary or external wall of the other building. 

Only that part of the wall (parallel to the allotment boundary or another building including any openings) within the specified limits above needs to be constructed to comply with Clause No protection is required for a wall at right angle or more to the boundary which is creating the potential fire source. 

Construction requirements for external walls  

External walls (including gables) that are required to be fire-resisting (as determined from the above section) must extend to the underside of a non-combustible roof covering or non-combustible eaves lining and must: 

  • have an FRL* of not less than 60/60/60 when tested from the outside, or 
  • be of masonry-veneer construction in which the external masonry veneer is not less than 90mm thick, or 
  • be of masonry construction not less than 90mm thick. 

Any openings in external walls required to be fire-resisting must be protected by: 

  • non-openable fire windows or other construction with an FRL of not less than -/60/-, or 
  • self-closing solid core doors not less than 35mm thick.

Sub-floor vents, roof vents, weep holes, control joints, construction joints and penetrations for pipes, conduits and the like must also comply with the openings requirements above. 

There are some concessions available for non-habitable room windows and also separate provisions for carports in certain circumstances . 

These fire-resisting walls must commence from the footings or ground slabs, and extend:

  • to the underside of a non-combustible roof covering, except that a wall may terminate not more than 200 mm from the underside of a non-combustible roof covering, where the area between the external wall and underside of the roof covering is sealed with a non-combustible fascia, gutter or flashing; or
  • to the underside of a non-combustible eaves lining.

*Fire-Resistance Level (FRL) is denoted with three figures – for example, FRL 60/60/60. The first figure denotes a ‘structural adequacy’ period of 60 minutes; the second figure denotes an ‘integrity’ period of 60 minutes; and the third figure denotes an ‘insulation’ period of 60 minutes. A dash indicates that there is no requirement for that criterion such as -/60/- where the criterion is 60 minutes for integrity only.

To find out more, contact HIA’s Building Services team.

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