Gutters overflow when more water reaches a section of gutter than it can carry to a downspout. The usual causes are clogs from leaves, needles and shingle granules; a gutter pitched the wrong way or sagging between hangers; too few or too small downspouts for the roof area; a gutter mounted too low or too far out from the roof edge; and water from a roof valley shooting over the front lip. Each one has a different fix, and you can usually tell which you have by watching from the ground in a rainstorm. This page is general information; your contractor makes the final call.
On this page: Signs · Causes · Rain check · Fixes · Basis · When to call
Signs of gutter overflow
- Water sheeting over the front lip, or pouring off one corner.
- A line of splash erosion or bare soil under the gutter.
- Stains or peeling paint on siding and fascia below.
- Standing water in sections of the gutter a day after rain.
- A wet basement or settling concrete near the house.
The usual causes
| Cause | What you see in the rain |
|---|---|
| Clog in the gutter or downspout | Overflow near the downspout; nothing coming out the bottom |
| Wrong pitch or sagging run | Water pooling and spilling at a low spot mid-run |
| Too few or too small downspouts | Long runs overflowing everywhere in heavy rain |
| Undersized gutter | Overflow along the whole length during downpours |
| Gutter too low or too far out from the roof edge | Water dripping behind the gutter or overshooting it |
| Valley runoff | A jet of water over the gutter at an inside corner |
A rainy-day check from the ground
- Watch where water escapes. Note whether it is at a corner, mid-run, near the downspout or all along the gutter.
- Check the downspout outlet. A weak trickle in heavy rain means a clog somewhere above.
- Look for sag and standing water after the rain stops.
- Look at the valleys. Inside corners where two roof planes meet send a lot of water to one spot.
- Check granules. Piles of granules in the gutter of an older roof can be a roof problem as well; see shingle granule loss.
Clean gutters from a stable ladder with a helper, or have them cleaned. Please do not walk the roof to reach them.
Fixes matched to the cause
| Fix | Use it when |
|---|---|
| Clean gutters and flush downspouts | Clogs are the cause. |
| Re-pitch the run and add hangers | Water stands mid-run or the gutter sags. |
| Add downspouts, or a diverter at the valley | Long runs or inside corners overflow. |
| Reset the gutter under the roof edge | Water runs behind or overshoots the gutter. |
| Upsize gutters and downspouts | A clean, well-pitched gutter still overflows in normal storms. |
| Replace crushed, corroded or rotted-through runs | The gutter itself has failed. |
Fixes that fail: sealant at leaking seams in a gutter that holds water, gutter guards tucked under the starter shingles, and heat cable as the cure for winter ice caused by attic heat loss.
Code and manufacturer basis
Gutter maker Englert recommends sloping gutters about 1/4 inch per 10 feet toward the downspouts, spacing hangers no more than 18 to 24 inches apart, mounting the gutter directly under the roof edge with its inner edge aligned to the drip edge, and sizing gutters to the roof area and local rainfall. The 2021 IRC, section R801.3, requires roof water on expansive or collapsible soils to discharge at least 5 feet from the foundation or into an approved drainage system.
For winter, NRCA’s Professional Roofing article on ice dams recommends keeping gutters sloped and clear with open downspouts, and advises against heat cables. Building Science Corporation’s BSI-046 makes the same point about heat cables. Englert, as a gutter maker, takes a different view and suggests heating elements in freeze-prone areas; we follow the roofing and building science guidance and fix attic heat loss first.
When to call
Call if gutters keep overflowing after cleaning, are pulling off the fascia, or are wetting the foundation. Overflow is often the first visible sign of rotted fascia and a missing kickout flashing. For choosing new gutters, see seamless vs sectional gutters and when to replace gutters. The roof problems guide has the rest.
Have your gutters and roof edge checked
Integrity Roofing and Painting is veteran-owned and family-run since 1990, an Owens Corning Platinum Preferred contractor with 650+ Google reviews. We look at the roof edge, gutters and downspouts together, because the cause is often one level up from where the water spills. Colorado Springs area: (719) 488-2800 or a free inspection. Denver metro: (303) 209-0152 or a free Denver inspection. Austin: (512) 610-5897 or a free Austin inspection. We reply the same business day.
Sources: Englert, Avoid these mistakes when installing gutters; 2021 IRC Chapter 8, section R801.3 (UpCodes); Colorado Geological Survey, Swelling soils; Professional Roofing (NRCA), Ice dam busting (2012); Building Science Corporation, BSI-046 Dam Ice Dam.
