Flashing Expansion and Contraction

As flashings cannot move in the longitudinal direction without stress, they should have some provision for expansion and contraction, particularly at joints.

As aluminium rivets have limited shear strength capacity, riveted joints in flashings can be prone to “popping”. Popping happens due to timber shrinkage, thermal expansion, or a combination of the two. The best solutions to minimise the frequency and consequences of breaking joints are to attach flashings with sliding clips or to provide expansion or slip joints at appropriate spacings.