Blocked Gutters: 7 Warning Signs Your London Property Needs Vacuum Cleaning in 2026

Most blocked gutters are silent for 12–18 months before the first damp patch appears inside. By then the cost of fixing it (replastering, repainting, sometimes treating timber rot) is 20–40x the cost of the gutter clean that would have prevented it. Here are the seven signs you can spot from the ground floor of your TW or SW London home.

1. Water cascading over the gutter front in heavy rain

The most obvious sign. Stand at your front gate during the next downpour and watch each gutter line. If water sheets off the front edge instead of flowing into the downpipe, the gutter is at least 70% blocked.

2. Watermark stripes on the brickwork

Long vertical brown or black stripes running down brick from gutter level mean water has been overflowing repeatedly. Once visible, these stripes don't wash off easily — they become permanent staining within 18 months.

3. Plants growing in the gutter

If you can see saplings, grass tufts or full ferns from the street, your gutters have had silt and moss accumulating for 2+ years. Birds drop seeds; they germinate in the silt; root systems then physically split the gutter joints from inside.

4. Birds repeatedly visiting the gutter line

Pigeons, starlings and house sparrows nest in blocked gutters. If you see them flying in and out of the gutter line in March–May, they've found nesting material in the blockage. Booked clean in late summer (after fledglings leave) — never disturb active nests.

5. Damp patches on upstairs internal walls

A horizontal damp line on the wall directly below an external gutter is a classic blocked-gutter symptom. Water pools in the gutter, soaks back into the brickwork, and finds its way through to the inside of upstairs rooms. Inspect immediately — left untreated, you're looking at replastering and re-decoration.

6. Cracked or sagging gutter sections

Wet leaves in a gutter weigh several kilograms per metre. After 6–12 months of standing water, plastic gutter sections sag, joints split and brackets pull from the fascia. A clean and a £40 bracket repair is dramatically cheaper than a full replacement run.

7. Pest activity around the property

Standing water in gutters is a mosquito breeding site in summer; rotten leaves attract rats; nesting birds attract mites. Increased pest activity around the eaves is often the first detectable sign of a long-blocked gutter.

What to do next

If you've ticked any 2 of the above, schedule a gutter vacuum clean within 4 weeks. The cost (£75–£175 in TW/SW postcodes) is a fraction of the damp repair work that follows. We send a phone-camera report after every clean so you can see exactly what came out — and any cracked or sagging sections we noticed during the job.