Code of Practice v3.0 Online
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.
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.
Most roofing profiles will resist far greater point loads when the load is applied to the pan of the profile rather than the rib. When the load is applied to the pan, the load is shared by the adjacent ribs and is applied to the flange under tension, rather than the flange under compression.
Testing loads may be applied to the pan or the rib depending of the profile shape and the design criteria. See 3.6.2 Roof Traffic.
Roofs that may be accessed by foot traffic must be designed to withstand a point load which is representative of a worker with a bag of tools. It is calculated at 112 kg, which equals 1.1 kN force.
In the case of a superimposed load, such as an air conditioning unit which is supported directly by the roof cladding, the unit weight per support and area of contact is calculated to arrive at point loads.
A point load on a roof is always positive or downward (+).
3.6.1A Point Load Test at the MRM
The designer must consider the degree and type of foot traffic that may be expected on a roof. The following requirements are subjective standards and must be considered in line with customer expectations, and building use and type.