Why Your Gutters Are Overflowing and What It's Doing to Your Roof
Overflowing gutters are one of the most common calls we get, and they're rarely just a gutter problem. Left alone, they can cause damp, rot and damage to brickwork.
Updated 28 July 2026
Overflow is usually a blockage, not a failed gutter
When water is coming over the front edge of a gutter during heavy rain, most people assume the gutter itself is broken or too small. In our experience it's far more often a blockage further along the run. Leaves, moss washed down from the roof, and general grit build up at outlets and in corners, and once the water can't get to the downpipe it has nowhere to go but over the front.
It doesn't take much to cause this. A gutter that's three-quarters full of debris behaves like a much smaller one, and during a proper Warwickshire downpour that's often all it takes to send water sheeting down the wall below. On a lot of houses in Leamington Spa and Warwick with older cast iron or asbestos guttering, the joints are also more prone to holding debris in the first place, which makes the problem worse over time.
What overflowing water actually does to a house
Water running down a wall face rather than through the guttering finds every weakness in the brickwork, pointing and render. Over a season or two this shows up as damp patches inside on upstairs walls, staining on the brick outside, and green algae growth where the wall stays wet longer than it should. On timber fascias and soffits it's worse again, because constant wetting is exactly what causes rot.
We've also seen cases where overflow has been running straight down onto a bay window roof or a flat roof extension below, which then takes far more water than it was ever built to shed. That's when a gutter problem turns into a leak inside the house, and by the time that happens the repair bill is a good deal higher than clearing the guttering would have been.
Checking and clearing guttering properly
A proper clear-out means getting up to the guttering, not just poking a hose at it from a ladder. We lift out debris by hand, check that outlets and downpipes are running freely, and flush the whole run through with water so we can actually see where it's still not draining. Any sagging sections, where the gutter has come away from its brackets and is holding standing water, get refixed to the correct fall.
It's also the point where we look at joints and seals, because on older guttering these perish and start to leak even when the run itself isn't blocked. Cracked union joints and gutter unions are cheap and quick to replace while everything's already accessible, and doing it at the same visit saves a second call-out.
Cast iron, uPVC and half round: what's on your house
A lot of the period properties we work on around Kenilworth and Warwick still have cast iron guttering, which can last decades but needs repainting and re-sealing at the joints periodically to stop it rusting through. uPVC guttering, which is what most newer housing stock has, doesn't rust but the seals and brackets do wear out, and UV exposure over the years makes the plastic more brittle.
When we're called out to a leak we'll always tell you honestly whether it's worth repairing a section or whether the whole run has had it. Patching a system that's failing throughout isn't good value, and we'd rather say that up front than keep coming back for the same job.
Trees, moss and seasonal maintenance
Houses under or near trees need gutters checked more often, plain and simple. Autumn leaf fall is the obvious culprit, but conifers shed needles all year round and these pack into corners in a way that's harder to spot from ground level. Moss washed off the roof itself is another major contributor, particularly on north-facing slopes that stay damp for longer.
We generally recommend a clear-out at least once a year, twice if the property has significant tree cover, and combining it with a quick roof check while access is already sorted. It's a small job compared with dealing with the water damage that follows if it's ignored for a couple of seasons.
When to call it in rather than DIY it
Clearing gutters from a ladder is one of the more common causes of falls around the house, and on a two-storey property it's genuinely not worth the risk for the sake of a job that takes us half an hour with the right kit. If your guttering is above a conservatory, extension roof or anywhere with awkward access, that's even more reason to get it looked at properly rather than balancing on a ladder against a fascia that might not take the weight.
If you're seeing recurring overflow at the same spot each time it rains, staining on brickwork, or damp patches appearing inside near the roofline, it's worth getting it checked rather than waiting for the next downpour to make the decision for you.
The short version
- Overflowing gutters are usually caused by blockages, not undersized guttering.
- Water running down walls instead of through gutters causes damp, staining and rot over time.
- A proper clear-out includes flushing the run and checking joints, not just removing visible leaves.
- Cast iron guttering needs repainting and resealing; uPVC seals and brackets wear out with age and UV exposure.
- Clear gutters at least once a year, more often near trees.
- Avoid DIY gutter clearing on ladders above extensions or awkward access; get it checked properly instead.