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NZ Building Code · Fire & AcousticBoundary walls within 1 metre
When an external wall sits close to a boundary, NZ fire rules step up how much fire resistance it needs and how many openings you can have.
An external wall close to a relevant boundary has to resist fire so a blaze can’t jump to the neighbour’s property — and theirs can’t reach yours. For houses and small sleeping uses, C/AS1 sets the rule by distance: the closer to the boundary, the more fire resistance you need and the fewer unprotected openings you’re allowed.
The distance rule
How the wall is treated steps down as it moves away from the boundary:
- Within 1 m of the relevant boundary — the wall needs an FRR of -/60/60, tested from the outside (fire) face, and no unprotected openings (windows, vents) are allowed in that zone.
- 1 m to about 1.5 m — a limited percentage of unprotected area is allowed; beyond that, openings open up as the wall gets further away.
Don’t forget the eaves and cladding
- Eaves and soffits projecting toward the boundary need protecting too — commonly -/30/30 to the underside. It’s an easy thing to miss.
- Cladding over a rated wall can be combustible, as long as the wall structure behind it delivers the FRR.
“Relevant boundary” isn’t always the legal boundary
For fire, the distance is measured to the relevant boundary — which can be a road centreline or an imaginary line between buildings on the same lot, not just the title boundary. Confirm what line applies before you assume you’re clear.
What this looks like on a tight site
Many infill houses on tight Auckland and Wellington sites sit 600–900 mm off the boundary — almost always the -/60/60 build (for example a GIB GBTL boundary system or an engineered alternative). On those jobs:
- Detail the eaves for fire protection where they project toward the boundary.
- Remember windows in that wall are out unless you pull the building back.
Plain-English guide, not advice. This page helps you understand and navigate the rules — it is general information, not design, engineering or consent advice, and it does not reproduce the copyrighted tables of NZS 3604 or any Standard. Always check the current Standard or Acceptable Solution and your BCA, and use a suitably qualified LBP, engineer or QS where it matters.
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Common questions
What FRR does a wall within 1m of the boundary need?
An FRR of -/60/60, tested from the outside (fire) face. No unprotected openings such as windows or vents are allowed within that 1m zone under C/AS1.
Can I put a window in a wall closer than 1m to the boundary?
No. Within 1m of the relevant boundary, no unprotected openings are allowed. From roughly 1m to 1.5m a limited percentage of unprotected area is permitted, and openings open up as the wall gets further away. Windows in a within-1m wall are out unless you pull the building back.
Is the 'relevant boundary' the same as my title boundary?
Not always. For fire, distance is measured to the relevant boundary, which can be a road centreline or an imaginary line between buildings on the same lot rather than just the legal title boundary. Confirm which line applies before assuming you're clear.
Do the eaves and cladding need fire protection too?
Eaves and soffits projecting toward the boundary commonly need protecting to -/30/30 on the underside, which is easy to miss. Cladding over a rated wall can be combustible as long as the wall structure behind it delivers the FRR.
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