To find a roof leak, start in the loft on a dry day and trace water stains uphill to the highest wet point — the entry is usually above and to one side of the internal drip. Common sources are slipped tiles, failed flashing and blocked valleys. A professional roof survey confirms it. Call 0122 763 4920.
Why Roof Leaks Are So Hard to Trace
The single most important thing to understand about a roof leak is that the water rarely enters where it appears inside. Water finds a gap in the roof, then runs along the underside of the felt, down a batten or a rafter, and drips through the ceiling at the lowest point it reaches — which can be a metre or more from where it actually got in. This is why chasing the ceiling stain almost never finds the leak.
The trick is to work uphill. Trace the water back from where it shows to the highest point it's wet, because the entry point is above that. On a pitched roof, that means looking up-slope; the higher the water travels before it drips, the further from the source the internal stain will be.
Traced the damp but can't find the source? Book a roof survey — the fee comes off any repair.
📞 Call 0122 763 4920Because water travels along roof timbers before emerging, the point of entry is typically higher up-slope than the internal stain — tracing damp to its highest point is the established method for locating a roof leak.
Source: BS 5250 (management of moisture in buildings) and NFRC leak-tracing guidance
How to Find the Source From Inside the Loft
The safest place to hunt for a leak is inside the loft, on a dry day, with a torch — never on the roof itself. Go up when it's light and, ideally, shortly after rain when the evidence is fresh. Look for water stains, damp patches, dark trails on the timbers, and any daylight showing through the roof. Follow wet timber upward to the highest damp point.
Watch for tell-tale signs: a dark, stained rafter or batten shows the water's path; a wet felt underlay with a tear or a slipped tile above it marks the entry; white salt-like deposits on brickwork around a chimney point to failed flashing. If you can time it, having someone gently run a hose over suspect areas of the roof while you watch inside the loft — starting low and working up — is how professionals isolate a leak, though this is a two-person job and the person outside must stay safely on a ladder or off the roof entirely.
If the loft is boarded, insulated over, or you can't safely access it, that's the point to stop and call a roofer. There's no shame in it — leaks are genuinely hard to find, and a professional does it faster and without the risk.
Common Leak Points in Canterbury Homes
Where a Canterbury leak comes from depends heavily on the property. On the post-war and 1960s estates at Hales Place and Thanington, the usual entry point is a slipped or cracked concrete tile — nail sickness lets tiles drop out of line and rain gets straight in. These are often visible from the ground as a gap or a crooked tile.
On the Victorian terraces around St Dunstan's and Wincheap, the leak is almost always the lead, not the slate. Flashing where the roof meets a chimney or a wall slips, splits along a fold, or was badly fitted decades ago, and water runs straight down the stack into the house. Tall Victorian chimneys make this the number-one leak source in these streets.
Under the heavy tree canopy near the Stour — Wincheap, South Canterbury, and out toward Sturry and Harbledown — the classic leak is a blocked valley. Autumn leaves fill the valley between two roof slopes, water backs up under the tiles, and it appears on the ceiling below. And across all house types, flat-roof extensions with ageing felt and the junctions around Velux windows are frequent entry points.
When to Stop Looking and Get a Survey
Call for a professional roof survey when you can't safely access the loft, when you've traced the damp but can't see the entry point, when the leak is intermittent and won't reveal itself, or when there are several possible sources. A roofer brings the equipment to inspect the roof safely and, increasingly, drone or thermal survey tools that pinpoint moisture without anyone leaving the ground.
A survey doesn't just find the leak — it tells you whether it's a simple repair or a symptom of a roof reaching the end of its life, which is worth knowing before you spend money. Our roof survey fee is credited against any repair work we then carry out, so finding the source costs you nothing if you go ahead with the fix.