Why should you clean your gutters?
TL;DR: Clearing your gutters costs £75 to £150 a year. When gutters are blocked water cannot reach the downpipe and soaks the same patch of wall every time it rains until it works into the cavity eventually causing internal damp which is expensive to rectify.
What happens when a gutter blocks?
A gutter catches the rainwater coming off the roof and carries it to a downpipe that takes it safely to the ground. When the run fills with moss, silt, leaves or anything else that has found its way up there, that water has nowhere to go, so it backs up behind the blockage and spills over the front edge in a steady sheet down the wall below. It will do this in the same spot every time it rains, which is what turns a minor blockage into a structural problem.
Water running down brickwork soaks the outer leaf, and on a cavity wall it can track across to the inner leaf, while on a solid wall it penetrates directly. Water sitting against the fascia board works into the timber and spreads along it, loosening the brackets that hold the gutter up and making the overflow worse as the run begins to drop. Water pouring off the same point also saturates the ground next to the house and erodes the soil around the footings.
We've found all sorts in gutters
The most memorable blockage we have come across was a tennis ball. It had lodged in a gutter run and sat there long enough for the gutter to fill up behind it, so every time it rained the water overflowed at the same point and soaked the brickwork underneath. Eventually it found its way into the cavity and the owners ended up with damp and mould on the inside face of that wall.
Clearing the ball and the debris packed in behind it stopped the overflow immediately. The brickwork dried out over the following months and the mould inside went with it, once the water feeding it had been cut off. A tennis ball is not even the strangest thing to come out of a gutter, since pregnancy tests have turned up more than once!
Blocked gutters often hide other problems
Around 75% of the cleans we carry out turn up something beyond the blockage itself, usually failed seals at the joints or a run that has begun to sag under the weight of standing water and debris.
A sagging run holds water permanently, which adds weight, pulls harder on the brackets and eventually opens up a joint. A failed seal drips onto the same patch of wall every time it rains, producing the same slow soaking as an overflow but at a fraction of the volume, so it takes longer to notice and longer to trace. Gutters sit at the very bottom of most people's property maintenance list and almost nobody gets close enough to look inside one, which means the person clearing them is often the first to see the condition they are in for several years.
Signs your gutters need clearing
Water spilling over the edge of the gutter during rain instead of running to the downpipe
A stain or streak running down the wall below one particular point
Plants, grass or small saplings growing out of the gutter line
A damp patch appearing on an internal wall, usually upstairs
A run that visibly dips in the middle
Water still dripping from the roofline hours after the rain has stopped
Should you do it yourself?
On a bungalow with clear access all the way round, clearing your own gutters is a reasonably safe job with a ladder, a scoop and a bucket. Above single storey it becomes more risky, because falls from ladders remain one of the most common causes of serious injury in home maintenance and the risk comes less from the height itself than from the temptation to lean sideways rather than climb down and move the ladder along.
Professional gutter cleaning has largely shifted to vacuum systems which are operated from ground level, with a camera mounted on the pole so the inside of the gutter can be inspected before and after the clear. If you do decide to do it yourself, work from firm level ground, move the ladder rather than stretching for the far end of a run, and have someone at the bottom while you work.