Zinc

Zinc is a traditional roof cladding material which weathers to a dark grey patina after environmental exposure; however, unlike galvanised steel, there is no spangle effect on the surface. Zinc roof panels and flashings are commonly 0.7 mm thick, although heavier gauges can be used. Zinc roofs are usually fully supported on sarking.

The staining potential of zinc run-off onto other surfaces is less than that of copper and lead. Flat zinc panels must be adequately vented from underneath and are available with a high-build lacquer coating to help prevent corrosion of the under-surface.

Zinc has approximately twice the thermal expansion coefficient as steel, so allowance for expansion must be made accordingly.

Under 7 °C the metal becomes brittle and is difficult to form without fracturing.

Zinc used for roof cladding generally contains small percentages of titanium and copper, which add to the properties of pure zinc.

Zinc is also available in a range of pre-patinated surfaces.