What is the correct slope for gutters?

Last Updated: October 23, 2026

Should gutters have a slope? Yes, toward every outlet

A gutter needs a slight, steady fall toward its outlet, because water in an open trough only moves when it has somewhere downhill to go. Gutters of Kent sets that pitch on every seamless gutter run it installs across Kent and South King County, with the work done by licensed and insured contractors, and it is one of the three things install day is built around: runs formed to length, hung on hidden hangers into sound wood, and pitched toward the outlets.

A common installation guideline is about a quarter inch of fall for every 10 feet of run, and some installers use up to about half an inch. On a 40-foot run pitched to one end, a quarter inch per 10 feet is a one-inch drop from end to end. That is enough to keep water moving and small enough that the gutter still sits close under the roof edge along its whole length.

Why a gutter needs fall at all

A dead-level gutter still drains, eventually, once the water stacks up high enough to push toward the outlet. The trouble is what happens in between. Water stands in the trough after every rain, and with it the fine grit washed off shingles, fir needles and moss fragments. That silt settles and thickens with each storm, and a level gutter becomes a shallow planter before it ever overflows.

Standing water also loads the run. Every foot of full gutter adds weight on the hangers, and a run that holds water between storms carries that weight much of the time. In Kent, where NOAA’s 1991 to 2020 normals for the Kent station show 96.7 days a year with at least a tenth of an inch of rain, a level gutter rarely gets a chance to dry out between October and January.

Too much slope causes its own problems

More fall is not always better. Each extra inch of drop moves the low end farther below the roof edge, and that has consequences:

• Water coming off the shingles can shoot past the front lip of a gutter that sits too low, especially in a heavy rain on a steep roof.
• The gap between the roof edge and the back of the gutter opens, so water that clings to the drip edge can miss the trough and run down the fascia. The drip edge and gutter apron guide explains how that edge is supposed to lap in.
• Water arrives at the outlet faster, and a small outlet or 2x3 downspout can back up even while the run itself is clear.
• A steep, obvious tilt along a long eave looks wrong from the street.

That is why the aim is a modest, even fall rather than the steepest one the fascia allows.

Long runs: pitched to two outlets

On a long eave, a single fall to one end has two drawbacks. The total drop grows with the length, so the low end hangs well below the roof line, and the whole run carries the whole roof’s water past every point where it could have left. The usual answer is to set a high point near the middle and pitch each half down to its own outlet at each end. Each half then carries half the water over half the distance, and the total drop at each end stays small.

Outlet placement and pitch are planned together. Where a valley lands near one corner, an outlet close to it can let that water leave before it travels, and the high point shifts to suit. The guide to how many downspouts you need covers outlet spacing, and the gutter size guide explains how capacity and outlets interact.

Visible tilt vs real function

From the street, a well-pitched gutter should look straight and parallel to the roof edge. The fall is there, but at a quarter inch per 10 feet it is hard to see without a level. A gutter you can clearly see sloping is usually either pitched much more than it needs, or sagging in one place.

Function is judged with water, not by eye. Fill the run near its high end with a hose and watch: the water should travel steadily to the outlet and drain away, leaving no puddle behind. Any stretch where it stops and pools is a low spot. That is the same logic as the water test at the end of install day, which runs water through the critical corners and outlets and confirms each downspout carries it away.

Brick, uneven fascia and older houses with settled framing can make a true line look crooked against the house. In those cases the gutter is set to a straight, falling string line rather than following every wave in the fascia, and any gaps at the back are handled with the drip edge rather than by bending the gutter to fit.

How evenness depends on hangers and fascia

The overall fall only works if the gutter holds its line between every hanger. Hidden hangers are commonly set about every two feet, closer where a run carries heavy debris or sits under a steep roof. If two hangers are too far apart, the gutter flexes under a load of water and debris and forms a dip between them. If one hanger is screwed into soft wood, it lets go and the run drops at that point.

That is why a slope problem and a sag can be the same problem seen two ways. The guide to gutter hangers compares hanger types and spacing, why gutters sag traces the sequence of failure, and sagging gutter repair covers re-hanging and re-pitching a sound run. Where the board itself has rotted, gutter and fascia repair comes first.

Checking your own gutters

From the ground in a steady rain, look for water spilling over the front at one spot along an otherwise working run; that often marks a low point. After the rain stops, look for gutters that drip for hours from one place. From a ladder, a level laid in the trough tells you which way it falls. If the pitch runs the wrong way, varies along the run, or you find standing water with grit at the bottom, it is worth a closer look. Gutter repair explains what correcting it involves, and you can Get an Estimate when you want each run checked.