A roof leak is two problems that feel like one. There is the water coming in, which is a roofing job and often needs daylight, dry weather and equipment. And there is the water already inside, which is doing damage right now and which you can deal with in the next ten minutes with a bucket and a screwdriver.
Do the second one first. Almost everybody does them in the wrong order.
Where the water actually gets in
Common entry points, roughly in order of how often they are the answer:
- A slipped or cracked tile or slate. The classic, and usually visible from the ground with binoculars.
- Failed flashing where the roof meets a chimney, a wall, a dormer or a vent pipe. Lead flashing lifts, cracks along the fold, or pulls out of the mortar joint.
- Blocked or broken guttering, which overflows back under the eaves rather than away from the building. Frequently mistaken for a roof leak and much easier to fix.
- A blocked valley where two roof slopes meet, usually with leaves and moss.
- Perished felt under the tiles, especially at the eaves where it has sagged and split.
- Around a rooflight or solar panel fixing.
- Condensation, which is not a leak at all. See damp and condensation before you go looking for a hole that does not exist.
Wind direction matters. A leak that only appears in driving rain from the south west is telling you which side of the roof to look at, and is very often a flashing or a mortar problem rather than a hole.
Inside first
- Cut the power at the consumer unit if water is near any light fitting, socket, or cable in the loft. Water tracks along cables. See the mains shut-offs.
- Clear the area. Furniture, electronics, books, carpet if you can lift it. Everything soft holds water and everything electrical is a hazard.
- Buckets, with a towel in each. The towel stops the splash and stops the noise, which matters more than it sounds at three in the morning.
- A plastic sheet or tarpaulin over what you cannot move, taped at the edges so run-off goes onto the floor rather than under it.
- Photograph everything before you clean up. Insurance wants the evidence and you will not want to go back for it later.
The bulging ceiling
An old lath and plaster ceiling behaves differently: it tends to sag and crack rather than let go in one piece, but it is heavier and its failure is no gentler. Treat it the same.
In the loft
If you can get into the loft safely, this is where you can do the most good with the least risk.
- Take a torch you can wear or hang, because you will need both hands.
- Stand on the joists, never on the plasterboard between them. The board will not hold you and you will come through the ceiling.
- Follow the water uphill from where it is dripping, along the rafter or the felt, until you find the point where it is arriving.
- Divert rather than block. A length of plastic sheet, a bin bag split open, or an offcut of guttering, pinned so it carries the water into a bucket, will keep a room dry for days.
- Move the insulation out from under the leak. Wet mineral wool is useless, extremely heavy, and it holds the water against the ceiling instead of letting it drain.
- Empty the bucket. Set an alarm. A forgotten bucket is a second, slower ceiling failure.
Going on the roof, and when not to
There is a real category of roof work that is fine from a ladder at the eaves: clearing a gutter, freeing a downpipe, pulling leaves out of a valley you can reach. That is worth doing, because a blocked gutter is a common cause and an easy fix. Getting onto the slope itself is a different activity and mostly belongs to somebody with a roof ladder.
Tarping properly
A tarpaulin over a damaged area buys weeks, and a badly fitted one buys nothing because the wind takes it in the first gust.
Sandbags or timber alone are not a fixing. They hold a tarp down in still air and they hold nothing in the wind that usually accompanies the weather that damaged the roof.
Fixing through a tile will crack it. That is acceptable on a roof that is already leaking and being repaired shortly. It is not acceptable as a permanent arrangement.
Afterwards
- Dry it properly. Weeks, not days. Warmth and airflow together; a dehumidifier if you have power for one. See damp and mould, because a roof leak that was dried badly becomes a mould problem that outlasts the leak by years.
- Do not put insulation back until the timbers are dry. Trapping damp against a rafter starts rot.
- Check the timbers. Soft, dark or crumbling wood near the leak means it has been going on longer than you thought.
- Keep the photographs and the receipts.
- Fix the cause properly. A tarp is a bandage. Every winter it stays on is a winter it might come off in the night.