The NZ Metal Roof and Wall Cladding Code of Practice is a comprehensive design & installation guide, and a recognised related document for Acceptable Solution E2/AS1 of the NZ Building Code.
Material thickness has a great bearing on strength. For residential buildings, 0.40 thickness material is most commonly used for corrugated and trapezoidal profiles, and this will normally be sufficient to withstand the statutory wind loads at typical spans and fastener spacings in up to High Wind Zones. In higher winds speeds, fastener patterns may have to be increased or purlin spacings decreased to accommodate wind loads (see 3.7 Wind Load) or thicker materials can be used.
Material with a 0.40 thickness is, however, very vulnerable to foot traffic damage in most profile configurations and requires careful and accurate foot placement to avoid buckling. In residential buildings with high foot traffic expectancy or highly visible roofs, eg, multi-level mono pitch roofs, roofs with UV collectors, flues, aircon devices or chimneys that need servicing, or prestige housing 0.55 material should be selected.
For commercial and industrial applications, 0.55 is almost universally used on the roof, and 0.40 or 0.55 on the walls.
0.40 and 0.55 are not the only thicknesses available; 0.48 is often used for high tensile trough sections, where it will often compare in strength to similar profiles manufactured from 0.55 G 300 material. 0.75 is often specified for heavy duty industrial roofs, and 0.63 is often manufactured for the Pacific Islands and other hurricane-prone regions. Other thicknesses are also available subject to minimum order quantities
G300 at 0.55 is the most common specification for spouting, flashings and ridging.