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NZ Building Code guide

💧 Weathertightness — the plain-English guide

E2/AS1 cavity construction, building wraps, flashings, brick veneer, internal gutters, roof underlay. Free, plain-English NZ Building Code reference for builders — 10 topics.

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E2/AS1 Cavity ConstructionThe 20 mm drained-and-vented cavity behind the cladding is the single biggest lesson of the leaky-homes era, and the…
E2 Risk MatrixThe E2/AS1 §3.4 Risk Matrix is how you prove , elevation by elevation, how weathertightness-risky a wall is — and…
Risk Matrix — Worked ExampleThe E2/AS1 risk matrix scores each elevation of a building. Worked example below — a typical 2-storey beachfront…
Building Wraps & UnderlaysThe building wrap (wall underlay) is the second line of defence behind the cladding: if water gets past the cladding,…
Flashings & JunctionsFlashings are the shaped sheet-metal pieces that bridge every junction and opening to throw water back out of the…
Brick Veneer CavityBrick veneer is a single skin of masonry standing in front of the real structural wall, separated by a 50 mm drainage…
Internal GuttersInternal gutters — the top cause of leaky home claims. AVOID where possible. If unavoidable, follow E2/AS1 §8.1.6 to…
Roof UnderlayRoof underlay is the breather membrane that drapes over the rafters/purlins below the roofing. It does two jobs:…
Wet Areas (E3/AS1)NZBC clause E3 Internal Moisture is about containing the water generated inside the house — showers, baths, splashing…
Waterproofing AS/NZS 3740AS/NZS 3740:2010 is the cited standard for waterproofing residential wet areas — bathrooms, ensuites, laundries,…

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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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