Copper

Roof cladding, gutters, and expansion and fixed clips should be made from a minimum of 0.6 mm half-hard temper strip, conforming to the British Standard, BS 2870.

Roll formed panels using secret fix interlocking edges that are made from half-hard temper, should not be silver soldered or brazed, because the heat required will anneal the copper.

When softened areas in half-hard copper can develop differential stress patterns, caused by expansion, which can result in fatigue and eventual failure of the metal.

Where penetration or other flashings require an amount of workability or are to be silver soldered or brazed, they should be made using fully annealed copper sheet or 0. 6 mm thick strip. See Copper.