How do I fix hard metal roof and cladding systems?

Unlike other forms of metal roofing and cladding, self-drilling fasteners are not used to fix directly through the hard metal sheet. This is because a dead fixed fastening would not allow for linear expansion and contraction of the extruded hard metal and could cause the metal to ripple or pucker.

Instead, cleats should be used. Cleats are designed to be fixed onto the substrate with fasteners and the hard metal cladding seam is then formed over the top. This system of attachment allows for linear expansion and contraction.

What cleats should I use?

There are two types of cleats, fixed and sliding, which can be utilised to allow for linear expansion and contraction of the sheet. Cleats are manufactured from stainless steel in various sizes to accommodate different seam heights. They are also available in different thicknesses offering various performance characteristics. Thicker gauges should be used on larger roofs or those with a high wind loading.

How should cleats be fixed?

The density of the cleat fixing pattern is determined by wind load calculations, with a greater density used in those areas that experience higher wind loads such as the roof ridge and edges. A cleat fixing pattern will normally be provided by the cladding manufacturer. When fixing into timber substrates, stainless steel nails or screws are used to secure the cleats, and when fixing into metal decking sheets or composite panels, stainless steel self-drilling fasteners should be used. The fasteners selected should have a low profile head style.

What substrates can cleats be used with?

Cleats are suitable for use with sheathing boards, metal decking sheets and composite panels. Stainless steel cleats and fasteners should always be used to secure hard metal, sheeting or components to eliminate the risk of galvanic corrosion.

Many manufacturers are associated with The Federation of Traditional Metal Roofing Contractors, who also provide useful information on fixing hard metal.