How to Fix a Leaking Gutter

A leaking gutter stains render, soaks fascia, and feeds damp at the wall head. Fixing it starts with diagnosis from the ground and a safe ladder setup, not with a tube of sealant smeared over the wrong spot. Most UK plastic runs fail at a joint, overflow from a blockage, or spill at a downpipe that will not take the flow.

Height work has a hard stop. If you cannot set a firm ladder with a second person footing it, or the eaves are above a height you trust, hire a gutter service. Treat clear guttering as the gate before any scoop or joint swap.

Find the wet patch, then the cause

Watch in rain or run a gentle hose from the high end of the run.

Job-specific detail: Stand back from the elevation in morning light. A dark stripe on the fascia under one clip almost always marks the drip line better than you can see from the ladder nose-on to the trough.

Ladder rules for this job

1. Level, firm base. Board under feet on soft ground.
2. Roughly one-out-to-four-up. Footed by a helper.
3. Belt buckle between the stiles. Move the ladder; do not stretch along the run.
4. Do not rest your full weight on plastic gutter as the only support.
5. Stop in high wind, ice, or on three-storey eaves without proper access kit.

Fix path (shortest honest route)

1. Clear before you replace parts

Leaves and silt make joints weep and outlets back up. Scoop debris away from the outlet, brush silt, and free the drop. Full method: how to clear guttering. Many “leaks” vanish once water can reach the downpipe again.

2. Water-test the joints

With the trough clean, run the hose slowly. Watch each union underside and the fascia. A dry length with one wet union is a seal job, not a whole-run renew.

3. Replace the failed joint

Match the profile family (half-round, square-line, ogee). Unclip, clean the seating length, fit new seals the right way up, and clip true. Step detail lives in how to replace a gutter joint. Do not use bathroom silicone as a permanent substitute for rubber gaskets on clip systems.

4. Check the downpipe path

If the gutter is dry but the shoe or hopper drips, or water backs up from the outlet in heavy flow, clear or renew the pipework. Cracked sockets and failed offsets are covered in how to replace a downpipe.

5. Retest in a proper flow

Hose again from upstream. Look for weeps at the repair and for overflow that means fall or capacity is still wrong. Persistent sag along brackets needs realignment later; a single joint swap will not lift a dipped run.

Mistakes that leave the wall wet

• Sealant over a grit-packed union so the drip moves two inches sideways.
• Mixing square-line parts into a half-round run because the colour matched on the shelf.
• Clearing debris by shoving it into the downpipe until the bend packs solid.
• Stretching from one ladder position until the joint racks open as you clip it.
• Ignoring a rotten fascia board that no longer holds brackets square.

When to call a pro

Stop for fragile roofs, cast-iron seized bolts you are not tooled for, asbestos-cement legacy gutters, and anything past a simple two-storey eaves you can reach safely. Call a gutter installer if short lengths keep cracking on clip-up (fall or line is wrong) or if damp inside the wall head suggests long-term overflow beyond a weekend fix.

Related reading: clear guttering, replace a gutter joint, and replace a downpipe.

FAQ

Is every gutter drip a failed joint?

No. Overflow from leaves looks like a leak from the pavement. Test after clearing. Joints drip in a fixed spot under a union; blockages spill along the front edge or at the outlet.

Can I seal a leaking gutter with silicone?

As a temporary emergency on a dry, clean surface, maybe. It is a poor long-term fix on modern clip systems. Replace the union and seals when you can. Silicone skins fail when the next clean peels them.

When should I replace the whole run instead of one joint?

When plastic is chalked and brittle in several places, brackets have pulled out along the elevation, or mixed historic repairs already fight each other. One sound joint in a dying run buys a season, not a decade.