How to Adjust Gutter Slope in 6 Steps to Improve Drainage

Measure the length of the section of gutter that needs adjustment. This can be difficult to do without two people on separate ladders. However, you don’t need an exact measurement in this step. You can also take an approximate length measurement while standing on the ground and estimating the starting and ending points.

If you made an estimated measurement and did not climb a ladder in the previous step, unfortunately, you can’t avoid it in this step. You need a precise measurement here.

Start at the end of the gutter farthest from the downspout. Climb the ladder and measure the distance from the edge of the roof to the top of the gutter. Repeat this measurement at the end closest to the downspout.

You can now calculate the slope. How much slope does a gutter need? For every 10 feet of gutter length, the end away from the downspout should be about 1/4 of an inch higher than the end closest to the downspout. If you have a 25-foot section of gutter, the far end should be 5/8 of an inch higher than the end near the downspout. 

If your current gutter doesn’t have enough slope, you’ll need to take it down and readjust it. If it has the correct slope on each end, take a few more measurements to be certain the gutter isn’t sagging in the middle, causing water to collect.

To fix the overall slope or a sagging gutter section, disconnect the entire gutter from the fascia board by removing the bracket screws. You can temporarily tack the gutter lower on the board to keep it from falling to the ground. You may have to detach part of the downspout to create space to work.

This step will be slow-going, as you’ll have to move the ladder multiple times.

If you notice any problems with the integrity of the fascia, consider repairing or replacing the fascia board during this process.

Using a pencil, mark the desired distance of the top of the gutter from the edge of the roof on the fascia board. Make the proper mark on both ends, taking the slope into account. 

Tack the chalk line on one end and stretch it tightly to the far end. Snap it to create the line the top of the gutter should follow along the fascia. If your section of gutter is lengthy, you may need someone else to climb a second ladder and snap the middle of the line.

Use the screws to reattach the gutter brackets, ensuring the top of the gutter is precisely following the chalk line. Again, this step will take a while because you’ll have to move the ladder quite a few times.

Once the gutter is tightly attached again, test the slope you’ve created. Place a garden hose in the gutter at the end farthest from the downspout. Turn the water on at a low flow rate and watch how it moves through the gutter toward the downspout. It should flow smoothly and quickly. 

If the water starts collecting or doesn’t flow steadily, the slope measurement is likely still wrong. Double-check your measurements or seek help from a gutter professional.