What is Building Code clause E2 weathertightness?
Short answer
E2 is the Building Code clause covering exterior weathertightness — keeping water out of buildings. It sets minimum standards for cladding, flashings, windows, and roof junctions. The Acceptable Solution E2/AS1 is the safe-harbour route most designs use; alternative solutions are possible but need extra documentation. E2 is the most-litigated clause in NZ — leaky-home claims pivot on it.
Source: Building Code clause E2. Updated May 2026.
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- Sets standards for cladding, flashings, window/door junctions, roof penetrations
- Acceptable Solution E2/AS1 is the safe-harbour route
- Alternative solutions need engineer / designer sign-off
- Risk score (E2/AS1 Figure 8) determines cladding choice eligibility
- Most leaky-home cases pivot on E2 non-compliance
The risk score and why it matters
E2/AS1 calculates a 'risk score' based on wind zone, height, complexity, cladding type, and eaves. The higher the score, the more limited the cladding options.
A high-risk score house (no eaves, lots of corners, multi-storey, high wind) can't use direct-fixed monolithic cladding under E2/AS1 — it needs a drained cavity. Get this wrong at design and you'll fail consent or worse, build a leaky house.
Common E2 failures
Inadequate or missing head flashings above windows. Direct-fixed cladding on high-risk junctions without a cavity. Wrong sealants used at junctions. Roof flashings cut short. Penetrations not properly weather-sealed.
Most of these are visible on the finished build if you know what to look for — but only specialists do. Independent inspections during framing and pre-cladding are standard on careful builds.
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Related questions
Sources: Building Code clause E2; E2/AS1 Acceptable Solution. General information for NZ homeowners, not legal advice. Building rules change and vary by council, so confirm critical details on the official source before acting. Last updated 2026-05.