A gutter end cap terminates the run of a gutter and is soldered for a watertight seal. Box gutters are traditionally found on older homes and are built into the roof, not installed on the edge. In a built-in box gutter, there are two types of end caps. One is at the low point, where the outlet tube is soldered to the gutter and the leader attached. The other is at a high point and acts as an expansion joint and is formed onto the corresponding end cap on the other side.
Copper vs. Tin Coated Steel
Box gutters are fabricated on site from copper- or tin-coated steel, which can be soldered. Tin coated steel is more affordable, but it needs to be painted every 8 or 10 years, whereas copper never needs any maintenance. The gutters are not nailed but are attached to the roof decking with bend backs and cleats to allow for expansion and contraction.
All seams of a box gutter must be bent back and pop riveted for extra strength before soldering. When soldering the joints do not use an open flame torch; the heat is intense and the underlying rafters might ignite and start a fire. Instead use a closed flame or an electric soldering torch.