Why do gutters leak?
Short answer. Gutters usually leak at joints, where sealant has dried and cracked from years of heat and movement, at corners and end caps that have pulled apart, at downspout outlets, and through holes rusted or punched into the metal. Water that seems to leak from a gutter is sometimes actually running behind it, because the drip edge is missing or too short.
The common causes
- Aging sealant. Every joint relies on sealant. Georgia summers heat gutters every afternoon and cool them every night, and that daily expansion and contraction eventually cracks the bead.
- Separated corners and end caps. Miters and caps are fastened with rivets or screws plus sealant. Ladders, falling limbs and sagging hangers pull them apart.
- Outlet failures. The collar where the downspout attaches can loosen or lose its seal.
- Sagging sections. A low spot holds standing water against joints and keeps them wet.
- Corrosion. Steel gutters rust through where water stands. Mixing copper with steel or aluminum speeds corrosion.
- Physical damage. Hail dents, ladder punctures and holes from old spikes or screws.
- Vinyl cracks. Vinyl turns brittle with sun and age and cracks at connectors.
Leaks that are not really gutter leaks
- Water behind the gutter: without drip edge, water runs down the fascia behind the gutter and drips from the back. Sealant will not fix it.
- Overshoot: water flying past the front lip below steep valleys looks like a leak from the ground.
- Overflow: a clog sends water over the front, often mistaken for a seam leak.
Pinpoint it
On a dry day, run a hose slowly into the gutter and watch from below. Drips at regular intervals point to sectional joints; a sheet of water from behind points to the roof edge. See drip edge explained, common causes of roof leaks and gutter sizing, seamless gutters and guards.