A roof sheds water in a sheet, and the gutter is what gathers that sheet and sends it somewhere harmless. While the system works, nobody thinks about it. If that job is not done, the rain keeps coming anyway. It sheets across the wall surface, soaks into the brick or stone, splashes back off the ground and pools beside the foundations. The damage that results is slow, often hidden, and rarely traced back to the gutter by the person living with it. A patch of damp on a bedroom wall, a flaking window sill and a rotten fascia can all share one cause: a channel that has been overflowing for years. Each blockage or failure starts small, and what follows for the walls, timbers and ground around an ordinary house depends on which part gave way and how long it went unnoticed.
What a gutter system actually does
A gutter system is more than the visible channel. It has five working parts, and trouble with any single one of them stops the others working.
- The gutter. The channel along the eaves that catches water as it leaves the roof edge.
- The brackets. They hold the channel at the right height and angle. A bracket that has loosened lets a run sag, and a sagging run holds a pool of water instead of passing it on.
- The outlet. The opening in the channel where water drops into the downpipe.
- The downpipe. The vertical pipe that carries water to the ground.
- The drain or gully. Where the water finally leaves the building, whether into a drain or a soakaway.
The roof's edge relies on the system too. Water coming off the lowest slates or tiles is meant to land in the channel, so the roof covering must overhang the gutter by the right amount. If the gutter sits too far from the edge, the water misses it. If it sits too high, it can back up under the lowest course.
The job is simple to state: collect, carry, and discharge away from the walls. Almost every failure comes down to one of those three. Water is not collected because the channel is full or tilted wrongly. It is not carried because a blockage or a flat spot stops it. It is not discharged properly because a downpipe has cracked or ends right against the wall.
How gutters block and fail
Blockage is the commonest failure, and it starts with debris. Leaves, moss washed from the roof, silt, small fragments of roof covering and the nests of birds all collect in the channel and at the outlet. Where the roof is shaded by trees, the debris arrives faster. Wet material rots into a sludge, seeds in it, and a plant is growing along the run within a season or two. Bird nests built in a gutter or downpipe are protected while in use, so work has to wait until the birds have finished with it.
Not every failure is a blockage. Some are mechanical.
Sagging and fall
Gutters are fixed to fall gently towards the outlet. When a bracket fails or a fascia rots, the fall reverses and water collects mid-run, overflowing at the lowest point. The weight of standing water then pulls the run further out of line.
Open joints
Plastic sections leak when their seals harden. Cast iron leaks when the sealant at its bolted joints dries. Either way, water drips from the joint onto the wall below, producing a vertical stain. The answer on a leaking gutter joint covers that fault.
Cracks and corrosion
Old plastic cracks in cold weather or under a ladder. Iron rusts through where paint has failed, usually at the back of the channel or the lowest point of the run, where water sits longest.
Frozen outlets
Standing water in a blocked system can freeze, and the ice splits joints and distorts brackets.
The pattern is the same each time. Water that should leave the roof edge by the channel now leaves it by some other route.
Damp walls and the problems inside the house
When a channel overflows, the water has nowhere to go but down the wall below it. A brick or stone wall absorbs water like a sponge. The wetting is greatest where the overflow lands, and below an overflowing outlet you can often see a green or dark vertical streak. That is the sign of a wall that has been saturated repeatedly.
Inside, the same water appears as penetrating damp. A patch of discoloured plaster, a bubbled surface, wallpaper that lifts, a musty smell in a corner of the room: all can be traced to an outside wall that has been soaked from above. Mould follows where the air is damp and still, usually behind furniture and in the corners of external walls.
Many people suspect rising damp when penetrating damp is the real cause. The two behave differently. Damp from above tends to be worst after heavy rain and to sit in patches under a particular window or beside a particular downpipe. A damp specialist or surveyor should confirm the cause before expensive treatment goes in, because injecting a damp-proof course will not cure water arriving from the gutter.
Chimney breasts and party walls suffer when a nearby valley or parapet gutter overflows, since water finds its way into the masonry and travels down. Our work on lead-lined gutters is described under lead roofing.
Rotten timber at the eaves
The timbers at the eaves take the first and heaviest soaking. Behind the gutter lie the fascia board, the rafter ends and, further in, the wall plate, a length of timber set on the masonry to carry the foot of each rafter. All of them are fixed in place and hard to inspect, and all of them stay wet when a gutter leaks onto them.
Timber that stays wet rots. The fascia is usually the first to go, because it is the nearest, and a soft fascia gives bracket screws nothing to hold. The gutter then sags further, the water leaks onto more timber, and the cycle quickens. Rafter ends soften next. Once rot has reached them, the repair is no longer a gutter job, and sections of rafter may need cutting out and splicing with new timber.
Soffits are hit as well. A wet soffit stains, flakes and drops, and where it holds a vent, the airflow into the loft is affected. The notes on looking after fascias and soffits show how to catch trouble before it spreads.
The wall plate is the part to worry about, since it carries the roof. A plate that has been wet for years can soften enough to let the roof spread slightly. That is rarer than surface rot, and a survey would confirm it, but it is the reason we look behind the fascia rather than only at the gutter.
Rot is not always visible from the ground. Peeling paint, a fascia that looks wavy and a gutter that no longer sits straight are the usual hints.
Masonry, frost and the ground around the house
Stone and brick are durable, but they are not immune to repeated soaking. In cold weather, water held in the surface freezes and expands, and the face of the stone can flake or break away. Bath stone is a limestone, and a limestone wall that is wetted again and again below an overflow will weather faster than the wall beside it. Soft lime mortar joints lose their grip, and the pointing falls out in the wet zone.
Water that reaches the ground does its own harm. A downpipe that has cracked, or one that ends in a gully that has blocked, spills water straight onto the ground beside the footings. If the ground there is saturated all the time, it softens around the foundations. Soil that is wet one season and dry the next may swell and shrink, and a house on clay can move as a result. Cracks that run diagonally from corners of windows and doors can be a sign of movement, and they need a structural engineer or surveyor, not a quick fill.
Water also splashes back from a hard surface. It carries mud up the wall and keeps the base permanently damp, and if the ground level is above the damp-proof course, water can bridge it.
Where a basement or lower-ground floor sits beside the wall, as many Bath terraces have, wet ground makes the problem worse. The area at the front, the lightwell, may have its own drain, and a blocked drain there fills with water that has nowhere to go but the wall. Check those drains whenever you check the gutters.
None of this is quick. Damage builds over seasons, not days, which is why it so often goes unnoticed.
Spotting trouble early, and what to do next
The best test of a gutter is to watch it in heavy rain. Stand outside and look for water spilling over the front lip, dripping from joints, or running down a wall where there should be a downpipe. Repeat the exercise on the rear elevation and beneath any extension roof. After the rain, look for staining, green growth and plants in the channel. Any of them says the system is not draining.
Other signs show without rain:
- Gutter lines that sag, or lean away from the wall.
- Rust streaks below the channel or at its joints.
- Paint peeling on the fascia, or boards that look soft or uneven.
- Damp or mould marks on the walls inside, near an outside wall.
- Water pooling at the foot of a downpipe.
A ladder is not the safe way to inspect a gutter above ground-floor height, and scaffold or a survey from the roof is better. Binoculars from the ground will show most of what you need.
Once there is a fault, the choice is between clearing, repairing and replacing. A blocked run needs clearing, a leaking joint needs resealing, and a failed or rotten system needs replacing. Repair comes first wherever it is enough. If the cause is a failed material, our guide to gutter materials compared helps you choose what replaces it, and a survey tells you what the timbers behind look like.
On the insurance side, many policies exclude damage from gradual deterioration and wear and tear, and a long-neglected gutter falls under that heading. Photographs and a roofer's report help if you do need to claim, but an insurer decides each claim on its own terms. See the gutters, soffits and fascias page for the work we do on a roofline. Before anyone calls, note which downpipe overflows in heavy rain and where the stains sit on the wall below, because that pattern usually points straight at the blocked section.