7 Signs Your Gutters Are Blocked

1. Water overflowing during rain

The clearest sign of all: water visibly cascading over the front lip of the gutter during rainfall rather than flowing along and down the downpipe. This means the gutter channel itself is full, whether from leaves, moss, silt or a combination, and water simply has nowhere else to go once it reaches the blockage point.

Even a partial blockage further along the run can cause overflow at a point some distance away, so overflow doesn't always tell you exactly where the blockage is, just that there is one.

2. Staining or streaks down the wall below

Vertical black or brown streaks running down render, brick or cladding below a section of gutter are a strong sign that overflow has been happening for a while, since a single heavy rain event rarely leaves a lasting mark. If you're seeing streaks, the blockage causing them has likely been present through at least one significant rain event, possibly longer.

3, 4, 5. Sagging sections, plant growth, and damp patches

A gutter section visibly sagging or pulling away from its brackets is often caused by the sheer weight of waterlogged silt and debris built up inside it, sometimes amounting to several kilograms per metre run. Small plants, weeds or even self-seeded saplings growing directly out of a gutter are a sure sign there's enough decomposed organic matter and moisture sitting in there to support plant growth, which takes months, not days, to establish.

Damp patches appearing inside the loft or on upper-floor ceilings, particularly after heavy rain, often trace back to a blocked gutter forcing water somewhere other than down the downpipe, see our dedicated guide on damp patches and blocked gutters for more on tracing this specific cause.

6 and 7. Birds and pests, and a sound gutter that suddenly sounds different

Increased bird activity around the roofline, or evidence of nesting materials in a gutter, often follows a build-up of silt and leaf litter that's created a soft, insulated base attractive for nesting. Similarly, if downpipes that used to gurgle or run audibly during rain have gone quiet, that can indicate water isn't reaching the downpipe at all anymore because it's overflowing before it gets there.

Any one of these seven signs on its own is worth a check; two or three together is a strong signal a gutter clear is overdue rather than optional. Catching them early, rather than waiting for an obvious problem like a leak or a collapsed section, is what keeps gutter maintenance a routine, low-cost job instead of an emergency repair.