The NZ Metal Roof and Wall Cladding Code of Practice is a comprehensive design & installation guide, and a recognised related document for Acceptable Solution E2/AS1 of the NZ Building Code.
Loads acting on roof cladding are generally classified into two types: point load and uniformly distributed Load (UDL)
Cladding reacts differently to a point load and a UDL. A point load is applied to a particular area, but a UDL impacts on the total area of the roof.
In many cases the point load will govern; it is often the most severe of the actions and will determine the purlin spacing of roof sheeting. Uniformly distributed loads vary over the roof area. They are greatest at the periphery and corners of a structure. Purlin spacing may have to be reduced, or the fastener frequency increased, to cope with local pressure factors.
Manufacturer's roof and wall cladding design load data should be published with both point and UDL performance values.