Cyclonic Steel Buildings

Cyclonic wind pressure sequences and high intensity rainful that is common in some Australian regions during the summer months requires a vastly different building and roof design, than structures in low wind areas. The Sheds n Homes kit building design software has the capacity to factor in consideration for buildings located in cyclonic wind regions.

Our cyclonic rated building designs feature:

  • Fully bolted shed frames that use Z purlins and girts with cleats (not top hats)
  • Purlins and girts with overlaps of 10% of the bay width (minimum requirement) PLUS an additional 100mm.
  • Decreased spacings on purlins and girts to suit the design criteria of your site
  • Roof cladding, fasteners and support members all passing Low-High-Low Testing (a standard cycle test method introduced by the BCA in 2009)
  • Larger gutters with flashings to cope with increased winds and rainfall

Your Cyclonic Building Checklist

When shopping around for cyclonic buildings, make sure you do your research thoroughly and compare quotes apples for apples. We recommend checking quotes against the below list of requirements.

In most cyclonic areas your building typically should be designed to minimum criteria of: Terrain Category 2.5; Importance Level 2 and Shielding Factor 1.0 (nearly always). Be careful of suppliers using anything less!

  • Check the weight of the building as large price differences are probably related to the mass of the steel.
  • Ensure both roof and wall sheeting has 0.47 TCT (Total Coated Thickness).
  • Roof screws should be Class 4 and supplied with cyclonic washers to suit your area.
  • Ensure that your building is designed to +0.7 CPI (Internal Pressure Coefficient).
  • Roller doors should be provided with an engineer certified Windlok kit to prevent them failing in a storm.
  • Check what fixing method is used. Be careful of dyna bolts for structural columns as they are not approved by the BSA and Australian standard!
  • For larger structures bridging should be added to portal frames to significantly reduce purlin roll
  • Cyclonic sheds and homes have a ridge cap designed to be cut into suit the profile roof sheeting to stop water ingress