Question answered
Why are my gutters overflowing?
The short answer
Gutters overflow for four main reasons: a blocked outlet or downpipe, a fall that no longer carries water to the outlet, brackets that have let the channel dip, or a run that is too small for the roof draining into it. Look at where the water leaves the gutter. A spill at one point suggests a blockage or sag, while spilling along the whole run points to size.
A gutter that spills over the front in rain is telling you something specific. It is blocked, it has lost its fall, its brackets have slipped or it is too small for the roof above it.
Read the pattern of the spill
Stand at a dry window or doorway during a downpour and see exactly where the water goes over. A single stream at one spot almost always means a blockage or a low point. Water pouring over the front all along a long run means the channel cannot carry the flow, either because the outlet is choked or the gutter is too small. Drips from the joints are a different fault, a failed seal, and are covered in leaking gutter joints.
Also note the weather. A gutter that copes with showers but spills in a storm may be working near its limit. Wind blowing rain sideways, or water pouring off a valley, can add more than the run was fitted to carry.
Jot down the date, the rain and the spot. Those few notes help the survey find the fault fast, and they save a repeat visit when the weather has changed.
Blocked outlets and the build-up behind them
Leaves, moss washed off the roof, grit from tiles, and in coastal streets feathers and gull nesting material all collect at the outlet, where the water drains into the downpipe. Once it narrows, the water backs up and spills. Check the downpipe too, since a blockage lower down looks just the same from above. Our page on how to clear a blocked downpipe covers the safe checks.
Clearing by hand from a stable ladder, with a scoop and a bucket, often solves it. If reaching the outlet means stretching sideways or standing on the top rungs, leave it to someone with a tower. Overhanging branches, a nearby tree or a roof full of moss keep refilling the channel, so cutting back the cause helps as much as the clearing.
A run that blocks again within weeks needs a closer look, because the real fault may be elsewhere.
Fall, brackets and the sagging channel
Every run needs a slight slope to its outlet. Manufacturers typically recommend a gentle fall, roughly 1:600 to 1:350 depending on the system, which is barely visible to the eye. Brett Martin's guidance is that supports should be no more than 900 mm apart. If the fall has reversed, water collects at the wrong end and tops the front edge.
Brackets loosen when fascia screws pull out of soft timber, or when a full, heavy channel drags the run down between supports. A sag of a few centimetres is enough to hold standing water and make the gutter spill at that point on its own. The fix is to refix or add brackets, and where the timber behind is soft, to repair the fascia as well. Look at seamless aluminium gutters for runs with fewer joints to open up.
The gutter can look level from the ground even when it is not, so a spirit level or a jug of water along the channel tells the truth.
Too much roof for too small a gutter
Some houses have a gutter that was never right for the roof. A large roof slope draining into a small half-round channel, a valley that delivers both slopes at one point, or a dormer or extension roof that sends its water onto a lower roof and then into a gutter below can overload a run. Adding an extra downpipe sometimes helps. A wider profile, or a second outlet, is often the better answer.
Old asbestos cement rainwater goods, found on some mid-century buildings, need care: HSE says careful removal of asbestos cement without breaking it is non-licensed work, but do not scrape, drill or break an old grey cement gutter yourself. If you are unsure of the material, ask us or an asbestos surveyor to look first, and read about asbestos in old soffits if the boards above look original.
Our survey measures the run, photographs the outlets and explains in writing which of these faults applies to your house.
When the overflow has damaged the roofline
Persistent overflow soaks the fascia, soffit and wall below. Look for green streaks on the brickwork, damp patches inside under the eaves, flaking paint and soft timber. If the damage has started, clearing the gutter on its own may not be enough. Boards and rafter ends need checking, and sometimes the run should be renewed with them. How long the replacement takes sets out what to expect, and the gutters, soffits and fascias hub shows the rest.
If water is already coming into the house, we make the roof safe first, then trace the cause. Never climb onto a roof or lean a ladder on a gutter in wet or windy weather. Send us a photograph of where the water spills, with the date written down, and we will look at it with you.
Gutter size and damp patches
Will a bigger gutter stop the overflow?
Only if size is the cause. A blocked outlet, a dip or a slipped bracket will spill whatever the gutter's width. We trace the cause first and recommend a wider profile or an extra outlet only where the roof above is shedding more water than the existing run can handle.
Can an overflowing gutter cause damp inside the house?
Yes. Water running down the wall or into the eaves can soak the brickwork, the fascia and the roof edge, and then appear as a stain on the ceiling or wall below. The damp is often well away from the spill itself, so the water has to be followed back through the structure.
Tell us about your roof
Describe what is happening and we will call you back to arrange a visit.
- Photographs of what we find
- A written quote with one total price
- Or call 01903 299063
10-year workmanship guarantee, in writing.