A damp patch on the landing ceiling makes you look up and wonder whether they can deal with it from the loft. The honest answer is partly. Inside the roof space you can find out a great deal: where the water enters, how far it has travelled and which timbers it has soaked. You can also stop it reaching the ceiling below and keep the damage from spreading while you arrange a repair.
What you cannot do from the inside is mend the covering that keeps the rain out. Tiles, slates, lead flashings, valleys and chimney joints sit on the outer face of the roof, and the only way to renew them is from outside with safe access. So this guide is about three things: tracing the drip path, containing the water and recognising what can and cannot be treated from within. It also covers what to tell a roofer so the visit goes straight to the cause. Stay on the loft boards throughout, switch the lights off at the mains if water is near a fitting, and never step between joists.
Why the stain is rarely under the hole
Water gets into a roof at one point and appears somewhere else. A tile cracks near the ridge, and the rain that passes through lands on the underlay, the sheet that lies over the rafters beneath the battens. From there it runs down the slope, follows a batten or a rafter sideways, and drips off a joint or a nail several feet away. By the time it reaches your ceiling, the drip may have left its starting point well behind. Older roofs with felt that has stiffened and torn give the water more routes to take, and an earlier patch can push the water to a new spot after each repair. That is why a stain on its own tells you very little. You need the trail above it.
What does that mean for tracing a leak?
It means starting at the stain and working uphill. The entry point is almost always higher than the wet patch, and often to one side of it. Look at the underside of the roof directly above the stain, then work upwards along the same rafter, and sideways along the battens.
Could it be something other than the roof?
Quite often. A dripping cold water tank or overflow pipe, a leaking joint on a pipe in the loft, and condensation on cold rafters all produce stains that look like roof leaks. Condensation tends to appear as a general dampness or black speckled mould and gets worse in cold spells without any rain at all. A leak from the covering arrives in rain, and it often stops when the rain stops. Our page on condensation or roof leak helps you tell the two apart.
Tracing the drip path from the loft
Pick a dry day for the first look and, if you can, a second look while it is raining. A leak is easiest to read when the timbers are wet and still marked from the last downpour. Take a bright torch, a pencil and some masking tape, and wear a dust mask because loft insulation sheds fibres.
What are you looking for?
Start with the obvious: daylight showing between tiles, which means a gap, and wet or flattened insulation, which shows where water lands. Then look for tide marks, rings on timber where moisture has dried and been wetted again, and for dark staining on battens and the sloping rafters. Check the underlay for tears, sagging or places where it hangs loose. Check around any pipe or flue that passes through the roof, and around the base of the chimney inside the loft.
How do you follow the water to its source?
Follow each wet rafter or batten uphill until the dampness thins and stops. The top of the wet trail is your best guess. Mark it with tape on the timber so you can show it to a roofer, and note whether there is a visible gap, a missing tile or a damaged piece of lead directly above. If it is raining and you can safely reach the spot, a second person outside with a hose is not worth the risk; leave water testing to a roofer with access.
Finally, look at the corners where a valley or an abutting wall meets the roof. These junctions, where two surfaces meet, collect a lot of water and are where flashing is most often at fault.
Containing the water while you wait
With a rough idea of the entry point, your job becomes damage limitation: keep the water away from the ceiling boards and the insulation, and keep the wiring dry. None of this mends the roof, so plan for a roofer to deal with the cause.
How do you catch a drip in the loft?
Lay a plastic sheet, or a large tray, on the boards below the wettest spot, and put a bucket where the water falls. If the drip is running along a rafter, a length of polythene draped from the timber into the bucket will carry it. Pull wet insulation to one side so it can dry, and do not press new insulation over damp timber. Move stored boxes and bags away from the area.
What should you do about the ceiling below?
A ceiling that is stained but dry can be left alone. One that is sagging holds water, so put a bucket under it and, from the side, prick the bulge where it hangs lowest with a screwdriver so it drains in one stream. Where a light fitting sits nearby, switch the circuit off, and keep clear of any wet fitting until an electrician has looked at it. Our page on water coming through the ceiling covers the same ground from the room below.
Let some air into the damaged room through a window. Resist the urge to blast the ceiling with a heater, because fast heat can crack plaster and drive moisture deeper into the boards. Moving air does the job slowly and safely. Keep the bucket checked as well: a heavy downpour can fill a small container faster than you expect, and an overflowing bucket in the loft soaks the ceiling you were trying to protect.
What can be held from inside the roof
A short list of faults can be improved, or held for a few days, from inside the loft. None of them replaces the repair, but each can stop a drip from doing more damage while you wait.
Which small jobs are realistic?
Channelling the water, as described above, is the main one. Others include moving or lifting wet insulation so the timber can dry, wedging a bucket or tray under the lowest drip, and tidying cabling out of the way of water. If you can see a small gap around a pipe collar or a vent from the inside, a roofer may tell you it needs a new collar fitted outside; do not try to fill it from within.
Is sealant from the inside any good?
Not really. A bead of sealant on the inner face of a crack does not stop rain entering through the gap on the outer face, and it can trap moisture in the timber. Outside, on a small dry area, a product can hold for a short spell, but from the loft side it only hides the clue. A sealed crack also stops water showing you where it travels, which makes the roofer's search harder.
What about foam or filler?
Avoid both. The Energy Saving Trust does not recommend covering a leaking roof with foam insulation, and says the roof must first be dry and sound. A roofer who finds foam over a damp patch has to cut it back before the real cause shows, which lengthens the visit and the bill. Keep tubes, tapes and expanding fillers out of the loft, and describe to the roofer anything you have already tried.
What cannot be fixed from inside
This is the part most DIY advice skips, and it is the most important. The things that keep rain out are on the outside, and they stay there.
The felt or membrane under the battens is out of reach from the loft. Putting in a new section means lifting the tiles and battens above it, which is work for the outside of the roof.
Which faults need a roofer outside?
A cracked or slipped tile, a lifted ridge tile, a failed valley, a tired lead flashing around a chimney, a split in a flat roof membrane and a gutter running into the wall all need outside access. A tile can be swapped in minutes by someone on the roof, but an interior effort to wedge or tape anything under it simply moves the problem. Valleys and flashings gather runoff from a whole slope, so when one fails the drip can be heavy, and a proper repair is the only answer. Our emergency and general roof repairs service starts with a survey of whichever part has failed.
When has the damage gone beyond a spot repair?
Soft, dark battens, rafters that give under a screwdriver, sagging felt across a wide area and leaks in several places at once suggest a slope that is wearing out. At that point a roofer will talk you through the choice between local repair and renewing the slope, and show you photographs of your own roof so the reasons are visible. Ask how much of the roof the quote covers and whether it is one total price including scaffolding and VAT.
Dry the loft and brief the roofer
The fix itself is the roofer's job, but how you prepare the ground shapes how well it goes.
What should you tell the roofer?
Describe when the leak appears (heavy rain, wind from one direction, or after a cold night), how long it has been happening and where the wet trail starts. Send your photographs and the marked sketch. A clear description lets the roofer check the likely entry point first and bring the right materials on the first visit. It also helps you judge a quote: a written price after a survey should name the part of the roof that has failed.
How do you dry the loft out?
Once the leak is stopped, let the timber and insulation dry. Airflow matters. Under BS 5250, as Marley sets it out, the felt in a cold roof that is not breathable wants an unbroken ventilation gap at the eaves: 25mm where the pitch is 15 degrees or less, 10mm where it is steeper. Insulation packed into that gap lets warm, damp household air settle on the felt and drip, which looks very like a leak. Draw the insulation back from the eaves rather than stuffing it in, and check the gap again after any loft work.
When can you redecorate?
Not until the cause is mended and the ceiling has dried right through. Painting over a damp stain locks moisture in and the mark returns. Cost turns on the roof covering, how hard the spot is to reach and what the survey turns up, and only the written total price that follows a survey settles it. Send us the sketch and photographs when you ask for one, and tell us whether the water appears in wind-driven rain or after any shower.
Part of our Emergency & General Roof Repairs in Crawley
Fixing a leak from inside: your questions
Can I fix a leaking roof from the loft without going outside?
You can trace the leak, catch the water and stop damage to the ceiling and insulation. You cannot mend tiles, slates, flashings or valleys from inside, because the covering is on the outside. Treat the loft work as protection and diagnosis, and book a roofer for the repair itself.
How do I find where a roof leak starts?
Work uphill from the stain along the wet rafter or batten until the dampness fades, and mark that point. Look for daylight, torn felt and rust or tide marks. The entry point is nearly always higher than the stain. Photograph what you find so a roofer can go straight to it.
Is it a leak or is it condensation?
A leak turns up in rain and dries when the rain stops. Condensation appears in cold weather without rain, as general dampness or mould on the underside of the felt and the timbers. Blocked eaves ventilation and bathroom air escaping into the loft are common causes. A roofer can tell you which after a survey.
