Curved Roofs


There are two main methods to clad curved buildings.
  1. Draped sheets, known as spring curving.
  2. Pre-curved sheets, either roll-curved or crimp curved.

For compliance with the requirements of the NZBC, designers should abide by the limitations of profiled metal cladding for curved roofs.

The curving process or crimping does not produce any strength enhancement for point or wind load. Curved roofs usually have maximum purlin spacings to avoid distortion.

Designers and contractors should be aware that light gauges such as 0.40 mm steel and 0.70 mm aluminium are likely to show distortion when used for curving. When asymmetrical-pan trapezoidal cladding is used for curved roofs and appearance is paramount, a heavier gauge cladding should be specified.

They are 'Restricted Access' roofs, which means that walking traffic should be restricted to within 300 mm of the purlins, and in the pan or over two ribs if they are adjacent to the vertical lap. Because of the changing pitch, edge protection must be provided, or a safety harness used when installing curved roofs. See Safety.

All side laps of curved sheets below the minimum pitch for the profile must be mechanically fastened and sealed.
Curved flashings are described in Curved Flashings.


Revision Category: 
1 - Minor Errata
Revision Detail: 

Grammar fix.

Draft Clause: