Rain gutters and downspouts are designed to divert and carry rainwater away from the foundation of your house, which helps maintain the integrity of its construction. They prevent soil erosion, damage to siding, and basement leaks. With a bit of effort and the right tools, you can install your gutters without hiring a contractor.
Measure the length of the roof that you’re working on. Rain gutters should be attached to the fascia and run the entire length of the roof, ending with a downspout. Use a measuring tape to determine the length of the gutter. If the gutter run measures longer than 40 feet (12.2 m), it should be positioned to pitch down from the middle, aimed toward a downspout at each end. If the gutter is shorter than this length, it will slope down to the left or right toward a single gutter.
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Whether you obtain your measurements from a ladder or the top of the roof, exercise caution: do not lean without support, place a ladder on uneven ground, or wear shoes without adequate traction.
Purchase at least the total length of gutter along with additional materials. Head to a home improvement store for gutter material, fascia brackets, and downspout(s). A fascia bracket must be attached to every other rafter tail, which is approximately every 32 inches (81.3 cm). For example, if the roof length is 35 feet (10.7 m), dividing by 32 inches (81.3 cm) nets 13.12, meaning you need to purchase 13 fascia brackets and at least 35 feet (10.7 m) of gutter.
Buy 1 downspout for gutters less than 40 feet (12.2 m) and 2 for anything longer. Avoid regions with hose bibs, sidewalks, and electric meters.
Gutters come anywhere between 4–6 in (10–15 cm) wide. Make sure you use the correct gutter based on your roof size and how often it rains in your area. If you don’t know which gutter size works best for you, look up a gutter size calculator online.
Mark the starting point of the gutter run 1.25 inches (3.2 cm) below the eaves flashing. The eaves flashing are the sheet metal pieces at the edge of the roof that protect the exterior of the building. Be sure to mark the starting point 1.25 inches (3.2 cm) below the flashing on the fascia —the straight, long board that runs along the lower edge of the roof.
If your roof is longer than 40 feet (12.2 m), mark the chalk line in the center of the fascia. Since the gutter extends downward from the center to the left and right, this marks the start.
If your roof is shorter than 40 feet (12.2 m), mark the starting point at the left or right of the roof.
Determine the end-point of the gutter run using a 1⁄2 inch (1.3 cm) downward slope. Locate the chalk line that marks the highest point of the gutter run. From here, mark a line in chalk on the fascia every 10 feet (3.0 m), moving down 1⁄2 inch (1.3 cm) for every point.
For example, if your gutter is 30 feet (9.1 m) long, it’s going to run from one end of the roof to the other. This means you will mark 3 chalk lines along the fascia, with the final one marking the end-point of the gutter run. The first line will be 1⁄4 inch (0.64 cm) down from the highest point, the second 1⁄2 inch (1.3 cm) down, and the end-point 3⁄4 inch (1.9 cm) down.
Install gutters 1–1 1⁄2 in (2.5–3.8 cm) past the end point so they catch water from overhanging shingles.
Snap a chalk line between the start and end of the gutter run. Locate the endpoints and hold a nail over each. Firmly hit the top of the nails with a hammer to drive them into each point. Hook one side of the chalk line to the nail at the start of the gutter run. Drag the string to the end point and hook it over the nail.
After attaching the chalk line, pull straight up from the middle and let the string snap.
Use blue and white chalk lines—red can bleed through the paint onto your fascia
Mark the location of each rafter tail at the chalk line. Rafter tails are usually spaced apart 16 inches (41 cm) on center and can be located by their nail heads. Place a clear chalk mark at each point using a piece of chalk.
Use a different color than the chalk line to help you distinguish them.