Gutter Leaking at a Corner

If your gutter drips at an inside or outside corner, you have found the hardest working joint on the whole system.

Why corners fail before anything else

Three things stack up at a corner.

More water passes through it. At an inside corner especially, two roof planes are draining into the same point. The volume moving through that joint during a storm is far higher than anywhere along a straight run.

It is a real joint, on every gutter. This is the part people find surprising. Seamless gutters are formed on site as one continuous piece along the length, which removes the joints in the middle of a run. But a corner requires two pieces to meet at an angle. That mitre is cut, fitted and sealed. Seamless does not mean jointless, it means no joints along the straight sections.

It flexes the most. Metal expands and contracts with temperature. At a corner, two pieces running in different directions are doing that against each other. Every hot afternoon and every freezing night works that joint slightly.

Put those together and the sealant at a corner is under more load, more often, than the sealant anywhere else.

Inside corners versus outside corners

Inside corners sit in the valley where two roof sections meet. They take a concentrated flow, and they are usually the first to leak on any house.

Outside corners wrap around a projection. They handle less volume, but they are more exposed and often catch more sun, which ages sealant faster.

Either way the mechanism is the same. Worth knowing which you have because an inside corner leak often shows up alongside overflow at the same spot, since that point is handling more water than the trough can take.

What a proper corner repair looks like

1. Clear and dry the joint completely. Corners collect debris precisely because flow slows there.
2. Remove the old sealant rather than layering over it. New sealant on top of degraded sealant bonds to the degraded sealant, not the metal.
3. Check the mitre is still sitting square. If the run has dropped or the corner has been knocked, the two pieces no longer meet cleanly, and no amount of sealant fixes a gap that moves.
4. Seal from the inside, where water pressure works with the repair rather than against it.
5. Let it cure.

Step three is where a repeat leak usually gets explained. If the joint is not square, the fix is rebuilding the corner, not re-sealing it.

The freeze and thaw factor here

Omaha does not freeze once and stay frozen. It crosses freezing repeatedly through the season, and each crossing flexes every joint on the house a little. A corner takes that flexing from two directions at once.

There is a worse version. Debris collects at corners because flow slows there. Wet debris holds water. That water freezes, expands inside the joint, and pushes the mitre apart from the inside. Come spring the sealant has been mechanically levered open rather than simply aged. This is why going into winter with a clear trough matters more than people think, and it is the honest benefit of both regular cleaning and guards.

When to stop repairing

One corner leak on a sound run is a straightforward repair. But if you have re-sealed the same corner more than twice, or corners are leaking at several points on the house, the sealant is not what is failing. Look at whether the runs are still properly pitched and firmly attached.

If a section does need replacing, we form seamless 5 inch and 6 inch K style on site in over 20 colors, so a rebuilt corner matches the rest of the house. Every installation carries a 1 year written warranty covering leaks and any part of the gutter that fails from how it was installed.

Estimates are free, with a $250 minimum on any job. If you have a leaking corner and a couple of other small things, get them all looked at on one visit.