Installing 6 in Gutters and Downspouts in Sections on a Metal Roof

Installing a 62 ft 1 1/2 in run of 6 in gutter from sections, rather than hiring a company for seamless gutter, is the approach shown on a metal-roofed house. The creator says the seamless option costs roughly three times as much as buying the pieces and doing it yourself.

Why 6 in gutter

The creator gives three reasons for 6 in over 5 in: it handles more volume of water, it looks a little better because it is bulkier, and it offers a shield effect against rain coming fast off a metal roof. On a shingled roof, he says, heavy rain can still overshoot the gutter.

Setting the slope

The center of the roof is found by measuring 31 ft from each side. The target slope is 1/4 in per 10 ft, which he says is a little over an inch and a half across the roof. Because the run is so long, the chalk line would sag, so he marks 3/4 in at the center and chalks from each end to the center. The gutter starts at the high side and slopes to the other end.

Outlet and end caps

The outlet is placed by holding the adapter against the house, with 2 in of gutter extending past the end of the roof. The hole is 2 1/2 in by 4 in. Corners are drilled with a 1/2 in bit and the cut is made with aviation snips, with eye protection. The adapter is set in a liberal bead of sealant and fastened with 1/4 in pop rivets. End caps come in left and right versions, with two rivets on the back and two on the front and none near the bottom.

Joints

Joints overlap by 6 in in the direction of water flow, since overlapping the other way is almost guaranteed to leak. A couple of beads of sealant are laced into the overlap, the joint is clamped, and six rivets go in the back and six in the front, kept up out of the bottom. Where a rivet gun can't reach, two sheet metal screws are used.

Hangers and cutting

Hangers go at least every 2 ft, lined up with divots, and are screwed to the fascia. The gutter is cut on a 12 in miter saw with a fine-tooth blade turned backwards, with eye protection, ear protection and gloves.

Downspouts

3×4 in downspouts match 6 in gutter; 2×3 in goes with 5 in. B elbows run along a wall and A elbows go out from it. A 9 in offset piece gets about 2 in added for overlap, and the main downspout length is the measurement to the ground plus 4 in, 86 in here. The upper piece must go inside the lower so water continues down. Hidden brackets are pre-drilled and fastened with 3 in construction screws on this new-construction house; on an existing home he recommends screws no longer than 1 3/4 in because longer ones could hit a wire. Stainless steel screws secure the downspout. He suggests drain pipes at the base to avoid eroding the ground.