COP:structure; profile-shape

3.13 Profile Shape 

The geometry of the profile shape determines the strength performance of the profile. Variation of profile shape from that tested will produce different results under load in pierced fastened profiles and may produce vastly different results in clip fixed profiles.


3.13.1 Corrugate Profile 

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.

3.13.2 Trapezoidal Profile 

The trapezoidal shape provides a greater water carrying capacity and provides greater spanning capabilities than corrugate (sinusoidal) profile. For nomenclature or description of the parts of the sheeting used in this COP, see 2.4 Product Geometry

The maximum available fastener density (fastener per square metre) on deep trapezoidal cladding profiles is usually lower than on corrugate, because of the wider rib spacing and longer spanning capability of stronger profiles. 



3.13.3 Miniature Profiles 

Various miniature cladding profiles are manufactured in New Zealand, the most common being known variously under the names of mini-corrugate, sparrow iron, baby iron and mini-iron.

Mini-corrugate is sometimes used for small roof areas, such as spires and awnings. It is most commonly used for wall cladding, parapets and internal linings where studs are normally spaced at 600 mm centres. The accuracy of the framing will determine the quality of finish obtainable.

Mini-corrugate has been produced in New Zealand for many years to the imperial measurement of 1" pitch and 1/4" height, which converts to 25.4 mm x 6.3 mm in metric measurement.

Some miniature trapezoidal profiles are also manufactured specifically for wall cladding.