A roof leak isn't always where you think it is. Water travels along rafters, down felt and across plasterboard before showing up as a damp patch — so the stain on your ceiling can be metres from the actual hole. Here are the seven most common causes we find on roofs in Oxfordshire, with what each one looks like and how it's fixed.
How do I find a roof leak if I can't see anything obvious?
Check the loft on a wet day with a torch — the entry point usually shows as a wet patch on rafters or felt directly above the daylight patch. Then trace upwards from there to the underside of the affected tile or flashing.
Can I temporarily stop a roof leak myself?
From inside, place a bucket under the drip and use a screwdriver to make a small hole at the lowest point of any bulging plasterboard (this controls where the water comes out). Don't go up onto the roof yourself.
How much does a roof leak repair cost?
Most one-off leak repairs are £180–£450 depending on access and what's causing it. Larger issues — full flashing replacement, ridge re-bed — run £450–£950.
Wind, age and freeze-thaw cycles loosen tile nibs and crack tiles. Even one missing tile lets driving rain through the felt within a few storms.
Refit slipped tiles, replace cracked ones with matching profile. Usually a 1–2 hour job per slope.
Lead around the chimney, dormers and valleys lifts, splits or pulls away from the brickwork. Cement fillets crack and let water track behind.
Strip old lead/cement, fit new code-4 or code-5 lead step flashings and soakers, properly chased into the brickwork.
Overflowing gutters drive water back into the eaves and behind the fascia. Common cause of damp patches near outside walls of upstairs rooms.
Clear gutters, check fall and brackets, replace any rotten fascia or soffit behind.
Perished felt/underlayment
Bitumen felt under tiles becomes brittle after 25–30 years and tears, letting any wind-driven rain straight into the loft.
Visible from the loft — usually means a re-roof is due. Strip and refit with breathable membrane.
Sand/cement mortar bedding ridge tiles cracks and washes out, leaving ridge tiles loose. Water tracks down into the roof void.
Re-bed ridges in fresh mortar — or fit a dry-ridge system for a longer-lasting solution.
Velux and other rooflights have rubber seals that perish after 15–20 years. Often shows as a leak in the kitchen extension on a wet day.
Replace the seal kit (Velux sell them) or, if the unit is old, replace the rooflight.
Failed flat-roof covering
Felt, EPDM or GRP splits, blisters or pulls away from upstands. Water finds the smallest tear and ponds before getting through.
Patch repair for small tears; full replacement if the membrane is widely failing or end-of-life.
Evans Roofing & Maintenance Ltd, Witney, Oxfordshire. Call 07960 482233 for a free written quote.