Why is my gutter overflowing?
Short answer. Gutters overflow because water cannot get out fast enough or never makes it in: a clogged outlet or downspout, a gutter with no slope or a sag that ponds water, a gutter too small for the roof area above it, a valley pouring concentrated water into one corner, or a gutter hung too low or too far back to catch fast runoff. Most cases are a clog, so check the downspout first.
Work through the causes in order
- Clogged downspout or outlet. The most common cause. Water stands in the gutter after rain stops. Clear the outlet and flush the downspout and elbows.
- Debris in the trough. Leaves, needles and pollen sludge slow water. Clean the run.
- Bad slope or a sag. Water pools in a low spot between hangers and spills there. Re-hang with hidden hangers into solid fascia and restore a fall toward the outlet.
- Valley concentration. Inside corners under valleys overflow first. Add a valley splash guard, a downspout near the corner, or a larger gutter.
- Undersized gutters or downspouts. Clean, well-sloped gutters that still spill in hard rain are too small. Six-inch gutters and 3 by 4 inch downspouts fix it.
- Gutter position. If the gutter sits too high or too far behind the roof edge, fast water from steep or metal roofs shoots over it.
- Guards. Matted mesh or hood-style guards can shed water over the front.
Overflow that is not really overflow
If water drips from behind the gutter rather than over the front, the problem is the roof edge: missing or short drip edge lets water roll back under the shingles and run down the fascia. That rots the fascia and rafter tails, and the fix is drip edge or gutter apron, not a cleaning.
Why it matters
Overflow dumps roof water at the foundation, splashes siding and soaks trim. In Georgia clay, that water stays against basement walls and crawl spaces for days. Fix the cause before the damage shows inside. Read gutter sizing and seamless gutters and drip edge explained.