Gutter corners leak because a corner is a joint, and the sealant in that joint dries out and cracks over time. Water then drips through the gap and runs down the fascia and the siding. Most of the time it is a small resealing job, as long as you catch it before the wood behind the gutter goes soft.
The short version
- A corner is two pieces of gutter joined together, so it is the weakest spot on the run.
- Even seamless gutters have joints at the corners and at the downspout openings.
- A drip at the corner can also come from a clog, a gutter that is too flat, or one that is too small.
- Cleaning the joint and resealing it fixes most corner leaks, if the metal is still sound.
- A leak left alone soaks the fascia board, and that repair costs far more than a tube of sealant.
Why do gutter corners leak?
Because the joint is held together by sealant, and sealant does not last forever. Over time, the joints between lengths of gutter can fail (opens in a new tab), and a corner has more joint to fail than a straight run.
Seamless gutters do not escape this. They have seams where the gutters connect to preformed corners and to downspout outlets (opens in a new tab), so the corners are still the place to look first. The same goes for the end caps, the small pieces that close off the gutter at each end.
We tend to think of sealant as a consumable. Our own Gutter Repair page says the same thing: the sealant in a joint dries out and cracks, and water that sits at the joint wears it out faster.
How can you tell it is the corner and not a clog?
Watch where the water comes out, and when. A bad seal drips from the joint itself. A clog or a flat gutter sends water over the lip or out of the nearest low spot, which can happen to be a corner.
| What you see | Likely cause | What to check |
|---|---|---|
| Drip from the underside of the joint, even in light rain | Cracked or dry sealant | Look inside the corner for a gap or flaking sealant |
| Water pours over the front in heavy rain | Clog or undersized gutter | Clear the debris, then watch the next storm |
| Water sits in the gutter after the rain stops | Gutter is too flat or sagging | Look for a low spot near the corner |
| Corner drips only near a downspout | Blocked or detached downspout | Run water down it and see if it backs up |
A full or backed-up gutter can push water out of any weak joint. A spillover of runoff is a sign of an undersized gutter system (opens in a new tab), and no amount of sealant fixes that.
Streaks on the siding are another clue. Fairfax County suggests you inspect the outside of the gutters and downspouts for streaks or watermarks (opens in a new tab) after rain, which is a good habit whether or not you see a drip.
Can you reseal a leaking gutter corner yourself?
Often, yes, if you are comfortable on a ladder and the metal is sound. Whether it is a corner or a straight joint, the repair is pretty much the same (opens in a new tab).
The steps look like this:
- Clear out the leaves and grit around the joint, and let the gutter dry.
- Scrape off the old, flaking sealant.
- Wipe the surfaces clean. This Old House says to use acetone to remove any residue, chalk lines, or debris (opens in a new tab) from the mating surfaces.
- Run a fresh bead of sealant along the joint and smooth it with a rag dampened with acetone.
- Run water through the gutter and watch the corner.
The cleaning step is the one people skip, and it is the reason a lot of fresh sealant lets go within a season. Sealant sticks to clean metal, not to dust.
One thing to keep in mind: if the gutter is high, steep underneath or hard to reach, skip it. A drip is not worth a fall.
When resealing is not enough
Resealing fixes a failed seal. It does not fix a gutter that is failing in other ways. Resealing will not hold when:
- The metal at the corner is rusted through. This Old House says that steel gutters riddled with rust holes (opens in a new tab) are better replaced entirely.
- The gutter is bent or twisted at the corner, so the joint never closes.
- The same corner has been resealed more than once and keeps coming back.
- The gutter holds water after the rain stops. Gutters should slope at least 1/16 inch per foot of run (opens in a new tab), so water has somewhere to go.
- The gutter is too small for the roof, so it overflows every storm.
In those cases, you pay for the same repair again and again. A new section, or new gutters, costs more up front and stops the cycle.
What does a leaking corner do to the fascia?
It soaks the fascia, the board the gutter hangs on, and wet wood rots. We see this a lot: water that stands in a gutter or runs down behind it rots the fascia first, then the ends of the rafters, then the first few inches of roof decking.
The annoying part is that none of this shows from the ground. The drip looks like a little dark streak, and the board behind it can be soft long before anyone notices. If you have a stain under a corner, press a screwdriver tip into the wood. If it sinks in, read what a fascia board is and why it rots.
Common questions
How long does gutter sealant last?
It depends on the sealant, the sun and how much water sits at the joint, so there is no single number. What holds true everywhere is that a joint with dried, cracked or peeling sealant is due for a fresh bead. Looking at the corners once a year, when you clean the gutters, catches it early.
Do seamless gutters leak at the corners?
They can. Seamless gutters have joints only at corners and downspouts (opens in a new tab), and most gutter failures happen at joints. They still leak less than sectional gutters, because there are fewer joints to fail. Our article on what seamless gutters are explains where the joints sit.
Can a clogged gutter make a corner leak?
Yes. Fairfax County says gutters should be cleaned free of debris at least once a year (opens in a new tab), and more often if you have trees close to the house. Under the big trees around Ellicott City, that usually means more than once. See how often gutters should be cleaned for the detail.
Is a leaking gutter corner an emergency?
No, but it is not one to leave for years either. A drip in one storm is a small problem. A drip every storm for a few years is a rotted board.
What to do next
If the corner is dripping and you would rather not climb a ladder, our gutter repair service reseals joints and checks the slope while we are there. We tell you if the gutter is past saving, and the quote is free. If the board behind it feels soft, the same visit covers that.
