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A leaking gutter joint can quietly cause damp walls, stained brickwork and rotten fascia boards, and it can lead to damp indoors if left. Fixing a leaking gutter joint usually comes down to one of three jobs: reseating the joint, replacing the worn gutter union, or resealing it with the right sealant. Most uPVC joints take under an hour and cost a few pounds in parts. Smearing silicone over a drip rarely lasts, which is why leaks keep returning. Here is what works, in the right order.
Work through the steps in order. Many joints stop dripping by step 4, so don’t jump straight to replacing parts.
What You’ll Need
Stand the ladder on firm, level ground and rest it against the wall, not the gutter, which can crack under the load. Have someone hold it. Falls from ladders are a real danger, so read the HSE ladder safety guidance before you climb. If the joint is above first-floor height, leave it to a roofer.
Dry the joint with a cloth, then run a hose in from the high end of the gutter. Watch where the water first appears and mark the spot. Water can travel along the underside of the gutter before it drips, so the real leak may be a short distance from where you see it.
Also check that the water is actually reaching the gutter. The roof edge should discharge into the middle of the gutter. If it overshoots, it can look like a leaking joint when the joint is fine.
Clear any blockage at the outlet, because a blocked outlet pushes water up and out of the joint. Then scoop out debris on both sides of the joint and wipe grit from around the seal.
Test with the hose. If the joint stays dry, you’re done.
Replacing the union is the more reliable gutter leak repair. Use sealant only if the part is no longer made or the joint just weeps.
Choose a dry, mild day, because sealant will not grip wet or dirty plastic.
Treat this as a stopgap on an old gutter. A new union will last longer.
Run the hose and watch the joint for several minutes, not seconds. Then look at the fascia and soffit behind it for staining or soft wood. If you find any, the problem is bigger than a joint.
Gutters expand and shrink with the weather, and the joint is where that movement shows up first. The usual causes are:
Some jobs are not worth the risk. Leave them to a roofer if:
For anything beyond a simple joint, our guttering repairs across Dorset cover fixing leaks, sagging runs, and cracked joints, so we fix the real cause once.
Extreme Pro Roofing fixes leaking gutters across Bournemouth, and nearby areas.
Get a Free Gutter Repair QuoteCold makes plastic gutters shrink, which can open small gaps around the seal, and grit trapped in the joint can hold it open. Water that freezes inside also adds stress. That is why a joint that is fine in summer can start dripping in January.
Tape may slow a drip from a crack, but it is harder to seal than proper gutter sealant, so use it only as a very short-term measure. For a joint, a new gutter union or correctly applied sealant is the better fix.
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Extreme Pro Roofing are roofers in Dorset providing professional roofing services including roof installation, roof repairs, roof maintenance, flat roofing, chimney repairs, leadwork, fascia, soffits and guttering, dry verge and ridge installation, conservatory roof replacement, loft conversions, Velux window installation and 24/7 emergency roofing across Dorset, Bournemouth, Southampton and Salisbury.
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