Why is expansion a consideration?

All roof sheeting and accessories expand and contract with changes in temperature, significant changes in length can occur in very long runs of roofing.

On a clear hot summer day, with no wind, the temperature in roof cladding can reach up to 80°C.

As shown in the table below, the expansion and contraction of metal sheeting and flashings can as high as 27 mm in any 30 m length with an increase of 75 degrees, so the inclusion of appropriate expansion joints is a must.