The uplift forces on fully supported roof cladding are transferred through the building through the clips and fasteners to the substrate.

The performance criterion is the number of clips or fasteners per square metre, which can be varied by the spacing of the clips or the width of the bays. The withdrawal load of the fasteners depends on the metal, shank diameter, shank type, penetration depth, and the type and thickness of the substrate.

The design load capacity of a clip can depend on the material of the clip and the thickness of the substrate.

The clips and fasteners should be able to withstand the wind design load, measured in kilonewton (kN), which is derived from the square measure of kilopascal (kP).

Maximum clip centres for different wind loads shall be derived Load/Clip Spacing, after making provision for local pressure factors.


    To improve the uplift resistance of fully supported roof cladding, the design options are:

    • reducing the width of the end bays;
    • increasing the metal thickness; and
    • placing the clips closer together.

    The clip spacing is determined by the wind design load, the thickness, type of substrate and the holding strength of the nails or screws. To comply with the wind design load criteria, the withdrawal load of the clip/nail assembly should be known for the thickness and type of substrate.

    Gable or verge panels must be wider than 400 mm, and the clips must be fixed closer together on the edges of all roofs in high wind design load areas.
    Unlike profiled metal cladding, the point load imposed on fully supported cladding is supported by the substrate.


    Draft Clause: