First, the golden rule: the stain is not the leak
Water almost never comes through the roof directly above the mark on your ceiling. It gets in at one point, runs along rafters, felt and old brickwork, and shows up somewhere else entirely — often metres away. So don't judge the problem by where the stain is; that's the end of the water's journey, not the start. It's why smearing sealant on the tile above the stain so rarely works.
What to do right now
Move furniture and anything electrical out from under the drip, put a bucket or towels down, and keep clear of any plaster that's bulging or sagging. Don't touch light fittings that are damp, and please don't climb on the roof — wet roofs hurt people every winter, and there's nothing up there that can't wait for a ladder and the right access. If water is actively coming in, call our emergency line — we answer seven days a week and we'll make the roof watertight first, then quote the permanent fix separately.
The usual suspects when it only leaks in rain
After enough East London roofs, the list is fairly short. In rough order of likelihood:
- A slipped or cracked slate or tile. On Victorian terraces the original fixing nails rust through — one slate slips and rain has a straight run at your felt, or at bare timber if there's no felt (common on older roofs).
- Failed flashing. The lead where the roof meets a chimney, parapet or neighbouring wall splits or works loose. Classic sign: the leak only appears in wind-driven rain from one direction.
- A blocked or overflowing gutter. Especially the parapet and valley gutters you can't see from the street — they silt up silently and then overflow inwards. If the leak comes with heavy rain but never drizzle, drainage capacity is a prime suspect. A gutter clean is the cheapest fix on this list.
- A tired flat roof. Felt laps, upstands and outlets on back additions and extensions fail long before the middle of the roof does.
- The chimney itself. Cracked flaunching, lost pointing or saturated brickwork — very often the "roof leak" is really a chimney problem.
Why heavy rain but not drizzle?
Light rain finds only the direct holes. Heavy rain finds the capacity problems — gutters that back up over their linings, parapet outlets that can't cope, and wind that drives water uphill under slates and through tired pointing. If your leak keeps rain-only hours, tell us what the weather was doing when it appeared; it genuinely helps narrow the search.
What not to do
Don't jet wash the roof, don't smear mastic over slates (it traps water and makes the real repair harder), and be wary of anyone offering to spray-coat the whole roof as a cure — it seals the symptom into the roof. The right sequence is: find the source, fix the detail that failed, then make good.
What the fix costs
Most straightforward leak repairs — a few slates refixed, a flashing repair, an outlet cleared and resealed — come in at a few hundred pounds. You'll get a free survey and a written quote before any work starts, and if it's bigger than a repair we'll tell you straight and price the options. Start with our roof leak repairs page, or just send a photo of the stain through the form.