Why Is My Roof Leaking?

The seven usual causes, in order of likelihood — and how each is confirmed.

Roofs leak for a short list of reasons, and experience gives that list an order. If your roof is letting water in, the culprit is very probably one of these seven — roughly in order of how often we find each one.

1. Flashings. The junctions — chimney, walls, roof windows — fail before the open roof does. Suspect them first, especially the hidden back gutter behind a chimney. 2. Slipped or broken tiles. Easy to spot from the ground, though the leak often shows indoors some distance downhill of the gap. 3. Valleys. Blocked with debris (water overflows the sides) or worn through (lead fatigue splits). 4. Ridge and verge mortar. Cracked bedding lets wind-driven rain in along the top and edges. 5. Perished felt. The covering looks fine; its safety net beneath has torn, so what was always getting past the tiles now gets past everything. 6. Gutters and roofline. Overflow soaking a wall reads exactly like a roof leak inside. 7. Not a leak at all — condensation. Damp lofts and ceiling spots with no rain correlation are usually airflow, not water ingress.

The single most useful thing you can do is note when it leaks: every rain, only heavy rain, only wind from one direction, or with no rain link at all. Each pattern points somewhere different.

Features

What's included

When does it leak? — the pattern narrows the search
Flashings and chimney junctions checked first
Valleys and ridge lines inspected
Felt condition assessed from the loft
Condensation ruled in or out honestly

Repair options

Repair or replace

Each cause has its page and its fix: flashing repair, tile replacement, valley repair, ridge re-bedding, felt and membrane work, guttering — and for the false alarm, loft condensation. If water is coming in right now, go straight to emergency repairs. And if you'd rather skip the theory: photographs of the ceiling and the roof outside, sent with a note of when it happens, get you a long way towards a diagnosis before anyone climbs a ladder.

Common questions

Frequently asked

The leak moves around — different spots after different storms. Why? +

That pattern usually means the felt beneath the tiles has multiple failures: water enters at one point but travels along the underlay and drops wherever the nearest tear is, which changes with wind direction and rain intensity. Wandering leaks are the classic signature of an underlay at end of life.

Can I find the leak myself from the loft? +

Sometimes — go up during rain with a torch and look for the glisten of a water track on the felt or rafters, then follow it uphill to its highest wet point. Mark it (chalk, tape) and note it relative to a landmark like the chimney. Even a rough location halves the diagnostic work. Don't walk on the ceiling joists' plasterboard, and don't go on the roof itself.

Why does it only leak in winter? +

Three candidates: wind-driven winter rain finding routes summer showers never test; blocked gutters and valleys after leaf-fall; or condensation, which is a cold-weather phenomenon and mimics a leak closely. The winter-only pattern is genuinely diagnostic — mention it when you get in touch.