AS 4055 Wind Classification for Housing

AS 4055 provides a simplified deemed-to-satisfy method for classifying wind loads on houses and sheds. Instead of a full directional wind speed analysis per AS/NZS 1170.2, this standard assigns a single wind classification based on four site parameters: wind region, terrain category, topographic class, and shielding.

Scope: AS 4055 applies to houses, sheds, and associated structures with roof height ≤ 8.5 m (single & two-storey), Importance Level 2, and 50-year design working life. For taller or more complex buildings, use a full AS/NZS 1170.2 analysis via the WindCode tool.

Site Location Optional

Enter an address to automatically detect the wind region, terrain category, and topographic class. Or skip and select parameters manually below.

1 Wind Region

Select the AS/NZS 1170.2 wind region for the site. Non-cyclonic regions (A) cover most of southern and inland Australia. Cyclonic regions (B, C, D) apply to tropical coastal areas.

2 Terrain Category

Classify the terrain roughness surrounding the site. AS 4055 uses TC2, TC2.5, and TC3. Sites in TC1 (open water) or TC4 (dense CBD) require a full AS/NZS 1170.2 assessment.

3 Topographic Class

Classify the topography at the site. Hills, ridges, and escarpments cause wind speed-up. Flat or gently sloping sites are T0.

4 Shielding

Assess the degree of shielding from surrounding buildings and obstructions. Shielding reduces the effective wind speed at the site.

5 Wind Classification Result

Wind Classification —

V_u (Ultimate) — m/s — 500-year return

V_s (Serviceability) — m/s — 25-year return

q_u (Ultimate) — kPa

q_s (Serviceability) — kPa

Wind Classification Summary

Table 3.1 — Design wind speeds and dynamic pressures for each wind classification.

Class	V_u (m/s)	V_s (m/s)	q_u (kPa)	q_s (kPa)	Typical Site

Classification Lookup Tables

Tables 3.2(A) to 3.2(D) — Wind classification for each combination of terrain category, topographic class, and shielding. The cell matching your current selection is highlighted.

AS 4055 vs AS/NZS 1170.2

When to use each standard for your project.

Use AS 4055 when:

Houses ≤ 8.5 m roof height (1–2 storeys)
Sheds and carports associated with housing
Importance Level 2, 50-year design life
Simple rectangular plan forms
Terrain categories TC2, TC2.5, or TC3
Quick classification without full analysis

Use AS/NZS 1170.2 when:

Buildings > 8.5 m or > 2 storeys
Importance Level 3 or 4 structures
Complex or irregular building shapes
TC1 (coastal) or TC4 (dense CBD) sites
Non-residential (commercial, industrial)
More detailed (potentially more economical) result needed

Note: AS 4055 wind classifications are inherently conservative compared to a full AS/NZS 1170.2 directional analysis. For borderline cases or cost-sensitive projects, a detailed wind assessment via WindCode may yield lower design pressures.

Notes & References

Wind classifications per AS 4055-2021 — Wind loads for housing (Standards Australia).
AS 4055 applies to houses and associated structures (Importance Level 2, 50-year design life) with average roof height ≤ 8.5 m.
Non-cyclonic classifications: N1, N2, N3, N4, N5, N6 (increasing severity).
Cyclonic classifications: C1, C2, C3, C4 (increasing severity).
V_u = ultimate design gust wind speed (500-year return period for IL2).
V_s = serviceability design gust wind speed (25-year return period).
Dynamic pressure: q = 0.6 × V² / 1000 (kPa), where V is in m/s.
Terrain categories in AS 4055: TC2, TC2.5, TC3 only. TC1 and TC4 require AS/NZS 1170.2.
Topographic classes: T0 (flat), T1 (moderate), T2 (steep), T3 (very steep).
Shielding: FS (full), PS (partial), NS (no shielding).
For a full directional wind speed analysis, use the WindCode tool (AS/NZS 1170.2-2021).
This reference is for guidance only. Site-specific conditions should be verified by a qualified engineer.

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AS 4055-2021