Gutters Leaking at the Seams? A Sealant Fix Takes an Hour
Seams leak when old sealant cracks and water finds the gap. Clean the joint, dry it, then seal it from the inside so the drip stops for good.
By Jamilur Rahman Updated November 5, 2026 · 7 min read
- Time
- 1 hour, plus cure time
- Cost
- Under $20
- Difficulty
- Medium
In this guide
Quick answer
Gutters leak at the seams because the old sealant dries out, cracks and pulls away as the metal expands and shrinks with the weather. Clear the gutter, find each drip with a hose, scrub the seam and let it dry. Then seal it from the inside with a gutter sealant that stays flexible, which holds long after a quick smear fails.
Free fix vs. permanent fix
Clean, test and re-hang
- Scoop out leaves and flush the gutter with a hose
- Run water from the high end and mark every drip
- Tighten loose hangers so water runs to the downspout
- Scrub off loose old sealant
How long it lasts: If the leak was overflow from a clog or a sagging section, this can fix it for good. A dripping seam keeps dripping, because nothing closes the gap.
Flexible gutter sealant, applied inside the seam
A seam is a gap between two pieces of metal that move with the weather. A flexible sealant fills the gap and moves with it. Cleaning shows you where the leak is, and the sealant is what closes it.
What to get: Gutter sealant for exterior metal gutters
How long it lasts: Often several years on a clean, dry seam. Look at it each fall when you clear leaves.
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What you'll need
-
Work gloves
Sheet-metal edges and old sealant are sharp
You have it -
Garden hose
To find the leak and to test the repair
You have it -
Stiff wire brush
Takes off flaking sealant and rust
You have it - Our pick Illustration
Gutter sealant
Pick one rated for your gutter material
- Illustration
Butyl gutter repair tape
For pinholes and small rust spots, not open seams
- Illustration
Hidden gutter hangers
Only if a section sags and holds water
Why it happens
Old sealant that cracked
Seams are sealed with a thin bead that dries out in sun and frost. Metal grows in heat and shrinks in cold, so over the years the bead cracks and pulls away from the metal.
Clogs that make water stand
When leaves block the flow, water sits on the seam, finds every weak spot and spills over the edge. What looks like a leaking seam is sometimes an overflowing clog.
Sag and the wrong slope
Gutters should drop about a quarter inch every 10 feet toward the downspout. A loose hanger lets a section dip, so water pools in the low spot and pushes on the joint.
Rust or holes beside the seam
Steel gutters rust from the inside where water sits. Small holes often show up next to a joint first.
Try this first (free)
Do these in order, starting with the simplest.
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Clear the gutter and flush it
Tool used: Work glovesFrom a ladder on firm ground, scoop out leaves and sludge, then flush toward the downspout with a hose. A dirty seam will not hold sealant, and a clog can be the whole problem.
-
Run the hose and mark every drip
Tool used: Garden hosePut the hose at the high end and let it run for a few minutes. Watch the seams and end caps from the ground and mark each drip with chalk or tape. Check that the downspout runs freely.
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Check the slope and the hangers
Water should run steadily toward the downspout, not sit. Tighten loose hangers or screws and lift any sagging section back into line.
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Scrub the seam down to clean metal
Tool used: Stiff wire brushBrush off loose sealant, grit and rust on both sides of the joint. Wipe it and let it dry fully, since sealant will not bond to a damp or dusty surface.
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Seal the seam from the inside
Tool used: Gutter sealantRun a bead along the whole seam and a little past each end, pressing it into the gap with a gloved finger. Keep it smooth so leaves do not catch on it. Keep rain off it for the cure time on the label.
IllustrationCheck price on AmazonTool for this step
Gutter sealant · Pick one rated for your gutter material
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Test again after it cures
Tool used: Garden hoseRun the hose again and watch the seam from below. If it still weeps, dry it and add a thin second pass.
When free fixes aren't enough
If the seam still drips after a clean and a hose test, nothing is closing the gap, and more cleaning will not. That is the job of sealant. If you find leaks at many joints, rust running through the metal, or a gutter pulling away from the house, patching will not last. A pro can tell you whether to re-hang or replace the run. Stop and call one if the board behind the gutter feels soft or rotten.
Buy the fix
Still stuck after the free fixes? These are the products we would look at.
| Pick | Product | Fixes | Who it's for | Buy |
|---|---|---|---|---|
| Best pick | Gutter sealant for exterior metal gutters | open seams, corners and end caps that drip | Anyone with a drip at a seam, corner or end cap who has cleaned the gutter first. | Check price |
| Budget pick | Self-adhesive butyl gutter repair tape | pinholes and small rust spots | Someone with a small hole, not a long open seam. | Check price |
| Upgrade pick | Hidden gutter hangers with screws | sagging that pools water at the seam | A section that dips or pulls away, so water sits at the joint. | Check price |
Gutter sealant for exterior metal gutters
Fixes: open seams, corners and end caps that drip
Look for: Made for gutters and rated for your gutter material; Stays flexible once cured, so it moves with the metal; Clear cure time and lowest application temperature on the label.
- Who it's for
- Anyone with a drip at a seam, corner or end cap who has cleaned the gutter first.
- Honest downside
- The metal is rusted through or the gutter is sagging. Sealant will not hold on bad metal, and a hanger fix comes first.
Self-adhesive butyl gutter repair tape
Fixes: pinholes and small rust spots
Look for: A width that covers the damage plus an inch on each side; Metal-backed or weather-resistant outer layer; Strong adhesive that grips clean, dry metal.
- Who it's for
- Someone with a small hole, not a long open seam.
- Honest downside
- A seam is open along its length. Tape bridges a hole, but sealant closes a joint better.
Hidden gutter hangers with screws
Fixes: sagging that pools water at the seam
Look for: A style that fits your gutter size and fascia; Rust-resistant coating or stainless steel; Screws long enough to reach solid wood.
- Who it's for
- A section that dips or pulls away, so water sits at the joint.
- Honest downside
- The wood behind the gutter is soft. Repair that first, or the hangers have nothing to grip.
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How we picked: How we picked: this page is based on gutter-care guides from home improvement and roofing groups, sealant instructions from product makers, and the problems and fixes owners report in reviews. We do not test products by hand.
Which leak do you have?
- Drip at a seam or corner: the sealant has failed. Reseal it from the inside.
- Water pouring over the front edge: a clog or a low spot. Clean and re-slope first.
- Drip from an end cap: clean and seal the cap's edge the same way.
- Water running down behind the gutter: a gap at the roof edge or flashing. Check this before blaming the seams.
- Drip from a hole or rust spot: patch the metal, or replace that section.
Ladder safety, in short
Set the ladder on firm, level ground and keep three points of contact. Do not lean out past your belt buckle. Stay well away from power lines, and skip wet or windy days. If a safe ladder cannot reach, hire the job out.
What to skip
Indoor caulk and thick smears over old sealant
Indoor-only caulks are not built for sun, frost and constant water. They crack or wash out within a season. Also skip sealing over a wet or dirty joint, or smearing a thick layer on top of crumbling old sealant. It looks fine for a week, then peels.
Frequently asked questions
Why do my gutters leak at the joints?
Why does my gutter keep leaking after I patched it?
How long does gutter sealant last?
Can I seal a gutter in the rain or the cold?
Should I replace the gutters instead?
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