The corrugate profile has been used in New Zealand for over 150 years and there has been only one significant change during that period. In the 1960s the steel grade used for roof and wall cladding changed from a low-strength steel of 250 MPa to high-strength 550 MPa. The number of corrugations also changed from 8 to 10.5, which enabled the sheets to be laid either side up, as opposed to over-and-under.
The performance of high strength steel corrugated cladding under point and wind loads is much higher than the more ductile grade (G300) still used for machine curving. G300 material of 0.55 mm has the same strength as 0.40 mm G550 material; designs using G300 should take the lesser strength into account. G300 material should not be used in lieu of G550, unless there is good reason to do it.
Mixing the two grades of corrugate profile should be avoided when possible. If they are used on the same job, particularly when they are overlapping, the manufacturer should adjust the profile shape to provide an acceptable fit.
Corrugate cladding is formed with a slightly asymmetrical overlap profile to a capillary barrier.