Before anything else, work out which problem you have. Water coming over the top edge of the gutter is overflow, and it is about capacity, pitch, or a blockage. Water coming from underneath, from a joint, or from the back is a leak, and that is a hole in the system. The repairs share almost nothing.
This article is about the second one. Leaks tend to appear in a handful of predictable places, because those are the places a gutter is joined, cut, or fastened, and every joint is a chance for water to get out.
Find the leak before you buy anything
- Wait for a dry day and bring a hose. Chasing a leak during a storm tells you where water is landing, not where it is escaping. On a dry day you control the water and can watch one section at a time.
- Start at the far end from the downspout. Run water into the trough and let it travel the full length. Working from the far end means you test the whole run, including the sections that only see water in a hard downpour.
- Watch from underneath, not from the ladder. Leaks show themselves from below. Have someone on the ground, or set the hose running and come down to look. Wet fascia, drips at a joint, or a steady trickle at a corner will be obvious.
- Mark every spot you find. A gutter that leaks in one place usually leaks in two or three. Marking them means the repair happens once instead of three times.
- Check the back edge as well as the seams. Water running behind the gutter and down the wall is a different failure: it means the back of the trough sits below the drip edge, so the roof is depositing water behind the gutter rather than into it.
Five places gutters leak
| Where | Why it happens | What it takes |
|---|---|---|
| End caps | The cap is crimped and sealed onto a cut end. Sealant is the only thing holding water back, and it is the first thing to fail. | Strip the old sealant back to clean metal and re-seal. Small job, and it lasts if the prep is done properly. |
| Inside and outside corners | Corners are two mitred pieces joined at an angle that flexes with heat. The joint works loose over years of expansion. | Re-seal, or replace the corner with a one-piece moulded fitting if the metal has deformed. |
| Seams between sections | Sectional gutter is joined every ten feet or so, and every joint is a seam. Gutter formed in one continuous run has far fewer, which is the main reason it costs more. | Re-seal from the inside. If the same seam has been sealed twice already, replace the section. |
| The downspout outlet | The connection between trough and downspout carries all the water and takes the most movement. | Re-seat and re-seal. A damaged downspout repair averages about $75 to $180 including materials (HomeGuide (2026)). |
| Fastener holes | Old spike-and-ferrule hardware leaves a hole through the trough. Once a spike loosens, the hole leaks every time it rains. | Replace with hidden hangers and seal the abandoned holes. |
When sealant is a waste of money
Sealant fixes a joint that has opened. It does not fix metal that has failed, and it does not fix a gutter that is leaking because it is full of standing water.
Sealing is the right call
- One or two joints leaking on an otherwise sound run
- Trough is straight, unpitted and holds its shape
- Fascia behind it is solid
- No rust-through or pinholes in the metal
Sealing will fail again
- That same seam has been sealed more than once already
- You can see pinholes, rust-through, or corrosion from inside
- Sagging section, so water stands on the joint permanently
- Deformed along its length from a ladder or a storm
The last one matters most in this area. A section that has lost its pitch holds water against a joint continuously instead of draining past it, and no sealant is designed for permanent submersion. Fixing the fall comes first, which runs about $85 to $250 for a slope adjustment (SquareDash (2026)). Seal a joint on a sagging run and you will be back up the ladder next season.
Where the water goes while you decide
A leaking gutter drips in one narrow spot, every time it rains, which is worse for the wood than the volume suggests. The drip usually lands on, or runs down, the fascia board behind the gutter. Repairing rotted fascia and soffit commonly runs $900 to $6,800 (This Old House (2026)), and it is a carpentry job, not a gutter job.
Below, a persistent drip at one point erodes a channel in the bed and drives water into the soil beside the slab. In a city that averages more than sixty inches of rain a year (NOAA / U.S. Climate Data), that is a lot of repetitions. Foundation repair from water-driven settlement averages around $5,100 (This Old House / Angi (2026)).
Doing it yourself
Sealing an end cap or a seam is one of the more approachable gutter jobs, provided the run is reachable from a stable ladder on level ground. Use a gutter-grade sealant rather than general silicone, apply it from inside the trough where water pressure pushes it into the joint rather than off it, and clean the surface back to bare metal first. Most failed repairs failed at the prep stage, not the sealing stage.
What makes it not worth doing yourself is height and diagnosis. About 500,000 people a year are treated for ladder-related injuries in the United States, and roughly 300 of those falls are fatal (AAOS / CPSC, via ANSI). And a leak that turns out to be a pitch problem will not respond to anything you buy at the hardware store.
When to call us
- It is a second-story run.
- You have sealed the same joint before and it came back.
- Water is running behind the gutter and down the wall.
- Fascia behind the leak is soft, dark, or shedding paint.
- Standing water sits in the section after the rain stops, which means pitch first.
We find the leak with water rather than guesswork, tell you whether it is a seal, a section, or a pitch problem, and say so when the answer is that a repair will not hold. Call us and we will come look at it.
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