We planned to start at the ends of the trough and work toward the middle, running two full-length pieces on each side, with two 44-inch lengths in the middle of the 39-foot gutter, where we would also create an expansion joint. To make all of the necessary bends, hems, and cuts, we used a Tapco Port-o-Bender Pro 2 brake and a cut-off wheel.
Each panel was formed with a trough in the middle and an upper and lower leg. On the 6-inch-long roof-side leg, we formed a 1/2-inch upturned hem that would receive the copper cleats that hold the panel in place. It’s important to gap this hem a little less than 1/8 inch to allow for movement when the copper expands and contracts. On the 4-inch-long crown-side leg, we made a 1/2-inch down-turned hem.
Prior to installing copper liner, we ran a continuous copper drip-edge along the top of the crown molding. Starting at one end of the gutter, we fit the panel in the plywood trough and then crimped the crown-side edge over the drip strip with an offset hand seamer tool. Once this was done, we fastened the roof-side hem off with the cleats, securing the 1 1/2-inch-wide copper cleats 24 inches on-center with 1 1/2-inch-long copper nails.
Without an expansion joint on a gutter this long, the solder joints would likely fail (the 20-foot run has the potential to expand approximately 1/4 inch, moving from the fixed end point toward the center). We began it by soldering a vertical “dam” in the trough. With the dam in place, we switched sides and fitted the three panels (two full-length panels and one 44-inch piece) at the other end.
We left a gap of a couple of inches between the two 44-inch-long panels. To receive the expansion-joint cap, we bent a 1-inch hem on the ends of the legs running up the roof and at the crown cap. Also, we bent on the top edge of dams 90° with an offset hand seamer.