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.

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.

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.

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.

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

Use a different color than the chalk line to help you distinguish them.

Place the gutter face down on 2 scraps of wood for support while you chisel the starter hole. Use a gutter piece with a pre-installed outlet to skip this step.

You can cut clockwise or counterclockwise—whichever you are most comfortable with.

Use rivets with a 1⁄8 inch (0. 32 cm) diameter.

After connecting the cap with rivets, apply a bead of silicone glue along the seam to waterproof it. Use a putty knife to smooth the silicone and press it into the joint.

Always cut your gutter on a flat surface. Use heavy-duty wire snips for smaller cuts. For gutters that run around corners, cut the appropriate angle—usually 45 degrees—at the applicable end.

Apply soap to the lag screws to make it easier for them to penetrate the fascia. Review the manufacturer’s recommendations for your type of gutter. Many gutter hangers come with long screws to go through your gutters and into the wood. To screw through the metal, turn them slowly at first so they can catch.

If you’re having trouble mounting the gutters, remove them and then place them on again, making sure that the edge closest to the fascia is underneath the fascia bracket hook before you rotate it.

Spray paint your brackets and gutters to contrast or match the house color.

After drilling in each screw, be sure to double-check the alignment of your gutter and ensure that it follows the chalk line. Take 100% silicone that is rated for exterior. [12] X Expert Source Ryaan TuttleHome Improvement Specialist Expert Interview. 13 January 2021. Silicone the gap between the fascia board and the gutter. [13] X Expert Source Ryaan TuttleHome Improvement Specialist Expert Interview. 13 January 2021. This will ensure that the water will run into the gutter and not behind it. [14] X Expert Source Ryaan TuttleHome Improvement Specialist Expert Interview. 13 January 2021.

Avoid aiming the tapered end toward regions with hose bibs, sidewalks, and electric meters. Join a 3–4 in (7. 6–10. 2 cm) PVC pipe to your downspout to divert rainwater into the ground if you want to get it further away from your home.