- 1). Plan the gutters so they all have a downward slope of 1/2 inch per 10 feet toward the downspouts. For long runs of gutter, you may want to slope two runs away from the center toward downspouts at the corners of the roof, or slope them into the center toward a common downspout. The layout depends on the design of your house and your drainage needs.
- 2). Drive a screw partially into the fascia at the high point of the slope, 1 1/2 inches below the metal flashing that forms the drip edge of the roof, or below the shingles. Hook the end of a chalk line onto the screw. Snap a line toward the downspout location that has a minimum slope of 1/2 inch for every 10 feet.
- 3). Use a drill to screw gutter hangers to the fascia along the line so there will be a hanger in the middle of each section of gutter and one at either end. Some hangers are mounted to hold the gutter from above and some are more like brackets that hold the gutter from underneath. The type you install depends on the gutter system you use. Heavy metal gutters, for example, require you to screw the brackets into the ends of roof rafters.
- 4). Fit a coupler onto the end of each section of plastic gutter that will be joined to another section. Some gutter systems are designed to connect with couplings that are fitted with rubber gaskets. Just push these onto the ends of the gutters to form a watertight seal. Others are designed to snap together, but you must seal the joints with caulk. You may have to solder sections of metal gutter systems together, which is best done on the ground. Hang each section of plastic gutter separately.
- 5). Cut the gutter section to the correct length with a hacksaw. Attach a downspout coupler to the gutter where the downspout is located. If you're installing a downspout on a metal gutter system, you may have to cut a hole in the gutter to attach the coupler. With a plastic system, you can snap this coupler into place.
- 6). Attach caps onto the ends of the lengths of gutter, either by snapping them in place, or by soldering or gluing them on.
- 7). Attach the downspouts to the downspout couplings and use 45-degree angle fittings to route them to the side of the house, then down to the ground. You can secure them to the siding by screwing in special fitted brackets. Be sure the water that flows from the downspouts moves away from the house.
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