Expansion Joints are a component in seamless rain gutter systems designed to protect the gutters from the effects of thermal expansion. Thermal expansion is the tendency for a material to expand and contract when exposed to changes in temperature.
According to SMACNA, the best way to protect your gutter system from thermal expansion is to split any long run into two separate runs, capping both ends and leaving ¼” gap between the top edges of the end caps. Then secure a small piece of aluminum to one of the end caps and fold it over the gap so that all rainwater over that gap is directed into either gutter.
Extra Keywords: Splice, Connect