Wind loads for housing
Simplified wind classification (N1–N6, C1–C4) for housing that meets geometric limits.
Overview
AS 4055 is the housing-focused simplification of AS/NZS 1170.2. It assigns a wind classification — N1 through N6 for non-cyclonic, C1 through C4 for cyclonic — based on region, terrain category, shielding and topography. The output drops directly into AS 1684, AS 2050, AS 2047 and other product standards.
Key Requirements
- Determine wind region (A, B, C, D).
- Assess terrain category for the site.
- Apply shielding multiplier (TS or FS) if neighbouring buildings shield the site.
- Apply topographic multiplier for hills, ridges, escarpments.
- Combine to find the wind classification.
How it's used in the NCC
The primary deemed-to-satisfy wind classification pathway for housing under Part 6.
Practical Notes
- Geometric limits apply — gable end, roof pitch, ceiling height etc. If the house exceeds these, use AS 1170.2 with an engineer.
- Get the classification documented early — windows, bracing, tie-down all depend on it.
Where to obtain
The full text of AS 4055 is published by Standards Australia and must be purchased — typical price A$150–400 per part. Always work from the current edition referenced in the NCC, not an older one.