Two identical sheds can need very different frames. One sits in a sheltered valley; the other is on an exposed ridge above the coast, or in the high country where snow settles on the roof. New Zealand’s weather and ground vary so much that a one-size-fits-all shed is either overbuilt for most sites or underbuilt for some. That’s why every Steelspan building is engineered for its own site.
Wind #
Wind is usually the load that decides a lightweight steel building’s frame, fixings and footings. The engineer works out the design wind for your exact site using the loading standard for wind actions. It depends on:
- your region, since some parts of the country see stronger winds than others
- terrain: open farmland and coast are windier than a suburb or a forest
- topography: hills, ridges and escarpments speed the wind up
- shielding from nearby buildings or landforms
- the building’s height and shape, and whether it has open sides or big doors
For smaller timber-framed buildings, you’ll also see wind zones, from low to extra high. A site’s wind zone affects whether some consent exemptions apply.
Snow #
In snow areas, the roof has to carry the weight of settled snow, which depends on the region and the site’s altitude. Steeper roofs shed snow better, and the frame and purlins are sized for the load.
Earthquakes #
Earthquake loads depend on the site’s seismic hazard, the ground conditions and the building’s weight. Steel sheds are light, so wind often governs the frame, but the engineer checks both. Heavy mezzanines, cranes or stored goods can change that.
Importance levels #
The loading standard also sorts buildings by the consequences of failure. MBIE guidance gives farm buildings, isolated structures and small structures under 30 m² as examples of importance level 1, while ordinary buildings are level 2. Buildings that house essential services or crowds sit higher. A higher level means bigger design loads.
What it changes in your shed #
Site-specific engineering decides the frame sizes, bracing, the spacing and number of purlin fixings, the cladding fixings, door specifications and the size of the footings. A cheap quote engineered for a “typical” site might fall short on an exposed one, and an exposed site always costs a little more.
After the storms #
Recent severe weather, including Cyclone Gabrielle in 2023, has reminded everyone that buildings need to be designed for the site they’re on. Doors and cladding fixings are usually where wind damage starts, so they matter as much as the frame.
How Steelspan does it #
Every Steelspan building is designed for its specific area and conditions by a chartered professional engineer, and comes with the engineering documentation the council needs. We’ve designed a number of buildings for extra snow loading, and supplied buildings for very high wind areas, including exports to the Pacific Islands such as Rarotonga, designed for cyclonic wind speeds and very high wind pressures. Talk to us early so your price reflects the conditions your building will stand in, with no surprises when the engineering is worked through for consent.
Talk to Steelspan #
Send us your address and we’ll engineer the building for that exact site. Use our Easy Shed Quote or call 0800 787 726.
