You notice it during heavy rain: instead of running neatly along the gutter and down the downpipe, water is cascading down the wall, dripping behind the gutter, or running down the back of the fascia board. The gutters might even be clean. This is one of the most common gutter complaints we hear in London — and one of the most misunderstood. Here’s what’s actually happening, why it matters, and how to fix it.
How water is supposed to behave at the eaves
On a properly set up roof, the bottom course of tiles or slates overhangs into the gutter. Rain runs down the roof slope, off the tile ends, and drops into the gutter trough. A detail called the eaves felt (or eaves tray) sits under the bottom tiles and directs any water that gets under the tiles into the gutter too. The gutter itself is hung with a slight fall toward the downpipe, so water flows away instead of pooling.
Water running behind the gutter means something in that chain has failed. The usual suspects:
Cause 1: The gutter has pulled away or tilted
Gutters are held by brackets screwed to the fascia board. Over time — heavy snow loads, ladders leaned against the gutter, or just years of thermal movement — brackets loosen or the fascia rots behind them. The gutter tilts outward or drops, opening a gap between the gutter’s back edge and the fascia. Water running off the roof overshoots the tilted gutter and runs down the wall behind it.
The fix: re-secure or replace the brackets, replace any rotten fascia, and re-hang the gutter at the correct fall. If the fascia is rotten, this is a good moment to consider full fascias and soffits renewal rather than patching.
Cause 2: Failed or missing eaves felt
Under the bottom row of tiles there’s a strip of felt (the eaves felt or underlay support tray) whose whole job is catching water that gets beneath the tiles and feeding it into the gutter. On older roofs this felt rots away — UV and age destroy it — and water that should go into the gutter instead drips into the soffit void or runs down behind the gutter.
The fix: lift the bottom tile course and fit new eaves trays. It’s a straightforward repair but it does involve disturbing the bottom of the roof covering, so it’s roofer work rather than a handyman job. Cost is typically £300–£600 for a standard run.
Cause 3: Tiles overhanging too far — or not far enough
Roof tiles should overhang the gutter by roughly a third of the gutter’s width. If a previous repair left tiles sitting too far forward, water shoots past the gutter’s back edge in heavy rain. If they don’t reach far enough — or slipped tiles have bridged the gap — water drops behind the gutter instead of into it.
The fix: reposition or replace the offending tiles. Sometimes a slipped tile sitting in the gutter is the whole story — a quick gutter repair visit sorts it.
Cause 4: Blocked or overflowing gutters
A gutter choked with moss, leaves, and silt can’t carry water away fast enough. In heavy rain it fills, overtops — and the overflow runs down the back, behind the gutter, soaking the fascia and wall. This is the simplest cause and the simplest fix: clean the gutters. Our guide to how to clean gutters safely covers the options, and how often to clean gutters in the UK tells you how frequently to do it.
Cause 5: No drip edge / incorrect gutter position
Some older installations have the gutter hung too low or too far from the fascia, so there’s a gap that wind-blown rain exploits. Modern practice fits the gutter tight to the fascia with the tile line discharging well into the trough. If the geometry is wrong, the gutter may need re-hanging to the correct position.
The damage it causes if left alone
Water running behind the gutter doesn’t just look bad — it does real damage:
- Fascia boards rot. Timber fascias soaked repeatedly will rot through, and then the gutter brackets have nothing solid to fix to.
- Soffits stain and decay. Water tracking back gets into the soffit void and the eaves of the roof.
- Walls get saturated. Constant wetting of the brickwork below the eaves leads to penetrating damp inside, green algae growth outside, and in winter, frost damage to the mortar and brick faces.
- Foundations. Water cascading down the wall lands at the base of the wall instead of being carried away — exactly where you don’t want it.
A £200–£400 gutter repair left undone can turn into a £1,500+ fascia and soffit replacement plus internal damp repairs. It’s one of those small jobs that’s genuinely worth doing promptly.
What the fix typically costs
For 2026 London price bands:
- Gutter clean and re-secure brackets: £150–£350
- Re-hang a gutter run at the correct fall: £250–£500
- New eaves trays fitted: £300–£600
- Section of guttering replaced: £200–£450
- Full guttering replacement (3-bed terrace): £600–£1,200
See our full guttering services page for what’s included, and our gutter replacement cost guide if the whole system is past its best.
Can you diagnose it yourself?
Yes, with care — you don’t need to go up a ladder. Stand back from the house during heavy rain and watch where the water goes. Is it overshooting the gutter? Dripping from behind it? Running down the wall in one spot (pointing to a bracket or joint failure) or along the whole run (pointing to fall or eaves felt issues)? Take a photo or video on your phone — it’s genuinely useful for the roofer diagnosing it later.
Get it sorted before the next storm
Water behind the gutter only gets worse with time. Victoria Roofing Expert Ltd is a family-run roofing contractor at 188 Camden High St, London NW1 8QP, serving Camden and all of London since 1982. We’ll find the actual cause — not just clean the gutter and hope — and fix it with fully guaranteed workmanship. 5.0 from 338 Google reviews.
Call 07848 256099 — open 24 hours — or request a free quote via our contact page.