Why are my gutters overflowing?

1. The outlet is blocked

The most common cause. Debris collects at the outlet, the hole that leads into the downpipe, and water backs up along the run. Sign: the gutter overflows near one corner and the downpipe below barely runs in heavy rain.

2. The gutter is full of moss and silt

Moss sheds off the roof, especially older concrete tiles, and settles in the gutter with leaves and grit. Over a few years it fills the channel completely. Sign: plants growing out of the gutter, or overflow along the whole length.

3. The downpipe is blocked

Leaves and moss wedge at a bend or a joint lower down. Sign: water spills from a joint halfway down the downpipe, or the gutter fills even though the outlet looks clear.

4. The gutter has dropped

A loose or broken bracket lets a section sag, so water pools there instead of flowing to the outlet. Sign: a visible dip, or overflow from the middle of a run. Cleaning helps, but the bracket needs refixing.

5. The gutter is too small for the roof

Some extensions and large roofs drain more water than the gutter can carry in a downpour. Sign: overflow only in the heaviest rain, even with clean gutters. This needs a bigger gutter or an extra outlet, not a clean.

What a gutter clear fixes

Causes 1 to 3: we vacuum the gutter from the ground, clear the outlets and check every downpipe. For causes 4 and 5, we'll photograph what we find so you know what needs repairing. See gutter clearing for prices, or read how often gutters should be cleared.