SA RoofingGutter leaking at the joint: why it happens and how to fix it
A gutter that drips from the same joint every time it rains is one of the most common gutter problems on Irish houses. This guide explains why it happens and what fixes it properly.
- Usual cause
- Perished rubber seals, or a gutter that has slipped out of its fitting
- Lasting fix
- A new union or fitting with fresh seals
- Sealant
- Only a stopgap on uPVC, because the gutter keeps moving in the joint
- Check first
- A sagging run or a rotten fascia behind the brackets
How uPVC gutter joints work
Most gutters on Dublin houses are uPVC, laid in lengths that are joined with separate fittings. A union bracket joins two straight lengths, corners turn the run around the house, stop ends close it off, and running outlets connect it to the downpipe. Each fitting has a rubber seal, and the gutter clips into it so that the seal presses against the gutter all the way round. When one joint starts to drip, it is usually a gutter repair rather than a sign that the whole system is finished.
The joints are designed to let the gutter move. uPVC expands in warm weather and contracts in cold, and a long run can change length noticeably between a summer afternoon and a frosty night. The gutter slides slightly within each fitting as it does so, which is why the seals are rubber rather than glue. When the seals are in good condition and the gutter falls towards its outlet, the system stays watertight for many years.
Why gutter joints leak
Most leaking joints come down to one of a handful of causes.
- Perished seals. After years of sun and frost the rubber hardens, shrinks and cracks, and stops sealing against the gutter.
- A gutter that has slipped out of its fitting. Thermal movement, a knock from a ladder or a loose bracket can pull the gutter end away from the seal.
- Lost fall. If a bracket breaks or the fascia behind it sags, water sits in the run and pools at the joint instead of flowing past it.
- Debris. Leaves, moss and silt build up against a joint, hold water there and can lift the seal.
- Mismatched parts. Fittings from a different manufacturer or profile may look the same but never seal properly.
- Installation faults on new gutters, usually a fitting that was not clipped in fully or a gutter cut too short to reach the seal.
Which joints go first
Sun-facing runs often leak first, because heat and UV age the seals faster, and the joints closest to a downpipe carry the most water.
Not sure what yours needs? WhatsApp us a photo and we will tell you what it looks like.
WhatsApp a photoOr get a free quoteCorner and outlet leaks
Corners and running outlets are the busiest parts of any gutter. A corner takes water from two directions, and an outlet carries the whole run's water down into the pipe, so a perished seal shows up there before anywhere else. An outlet leak can also come from a blocked downpipe, which backs water up into the outlet until it overflows at the seal. Before replacing an outlet, it is worth checking that the downpipe below it is clear, and our guide to blocked downpipes explains how to tell.
Can a leaking gutter joint be fixed?
Yes. A leaking joint on a uPVC gutter is usually fixed by fitting a new union or fitting with fresh rubber seals, if the gutter on either side is sound and still falls towards the outlet. Sealant only stops the drip for a while on plastic, because the gutter keeps moving in the joint and the sealant cracks away.
Sealant, a new union or a new section
Gutter sealant is sold for exactly this problem, and it can stop a drip for a while. On uPVC it rarely lasts. The gutter keeps moving within the joint, the sealant cracks or peels away, and the leak comes back, often worse because the joint is now dirty and hard to reseal. Sealant is a reasonable stopgap on a cast iron joint, where there is no movement to accommodate, but on plastic it treats the symptom.
The lasting fix for a leaking uPVC joint is a new union or fitting with fresh seals, matched to the gutter profile. If the gutter ends have cracked or distorted, a short new section goes in as well. Where several joints along a run are leaking, the seals are all the same age and the rest will follow, so replacing the run often makes more sense than repairing one joint a year.
When it is the fascia, not the gutter
Sometimes the joint is fine and the problem is behind it. Gutter brackets are screwed to the fascia board, and if the timber has rotted, the screws lose their grip, the brackets drop, and the gutter loses its fall or pulls apart at a joint. Refitting the gutter to soft timber does not last. The signs are flaking paint, soft spots or black staining on the fascia, and a gutter that sags between brackets. In that case the fascia needs attention first, which our fascia and soffits page covers.
What affects the cost of fixing a leaking gutter joint
The fitting itself is inexpensive, so access and labour make up most of the cost. A joint on a bungalow can be reached from a ladder, while one on a three-storey house or above a conservatory needs more access equipment. The number of joints, whether matching fittings are still available for an older or less common profile, and any work needed on brackets or fascia all add to the job.
Our guide to gutter replacement costs gives rough Dublin ranges for small gutter repairs and full replacement, and if the gutters are also full of leaves and moss, we can clear them out on the same visit. A photo of the dripping joint on WhatsApp helps us bring a fitting that matches your gutter profile, and we confirm the price after a free look at the whole run.
Frequently asked questions
Why are my new gutters leaking at the seams?
On a new uPVC system the usual cause is a fitting that was not clipped in fully, a gutter cut too short to reach the seal, or a run without enough fall. These are installation faults and are normally quick to put right.
What is the best sealant for leaking gutter joints?
On uPVC, sealant is only a short-term fix, because the gutter moves within the joint and the sealant cracks away. A new union or fitting with fresh seals is the lasting repair. Sealant is more useful on cast iron joints, which do not move.
Can one leaking joint be fixed without replacing the gutter?
Yes. If the gutter either side is sound and still falls to the outlet, the leaking union or corner can be replaced on its own.
Why does my gutter only leak at the joint in heavy rain?
In heavy rain the water level in the gutter rises above the part of the seal that is still working, or water backs up from a partly blocked outlet or downpipe. Clearing the gutter and checking the fall usually shows which it is.
Why is water dripping from underneath my gutter?
It usually comes from a failed seal at a union or end stop, a crack in an old section, or water creeping back along the underside from a gutter that is overflowing at the edge. Watching it during rain normally shows which, and most of these are fixed without replacing the whole run.
Is a dripping gutter joint worth fixing?
Yes. A constant drip soaks the wall below, stains render and brickwork, and can rot the fascia behind the gutter, all of which cost more to put right than a new fitting (see what replacing fascia costs).