How long can a tarp stay on a roof?

Sheeting does one job: it sheds water. It does nothing for the structure beneath, and it cannot match the way tiles or slates overlap to move rain down a slope. Even the heavy-duty sheets roofers use are plastic fabric under tension, fixed with timber battens, and they live a hard life on top of a house.

Wind is the first enemy. Even a well-fixed cover moves in gusts, and each flutter works at the hems and the screw holes. Sun is the second: ultraviolet light slowly makes plastic brittle, so a sheet that looked tough in the first week can crack at the folds later. Frost, rain pooling in a dip and debris from nearby trees finish the job.

For these reasons no responsible roofer will name a date by which a tarp is certain to fail, or promise that it will last a given time. What they will say is that it should be checked regularly and replaced with a proper repair as early as practical. Our page on temporary roof repairs sets out the other short-term options and their limits.

The obvious problem is that it tears or blows off, putting the roof back where it started, often in worse weather. The less obvious ones are quieter.

Moisture gets trapped. Where the sheet sits close against slates or the felt, air cannot move, and condensation or water that got in at the edges stays in the timbers. Damp battens and rafters begin to rot, and the repair that would have been simple grows into one involving carpentry. In the loft, wet insulation loses its value and starts to smell.

Ponding is another trouble. A slack section collects water, the weight pulls the fixings and the sheet drags tiles with it. The edges can also chafe slates or crack brittle tiles as they move. If water is still reaching the ceilings below, mould follows. A bulge in the plaster is a sign of a larger problem, and our page on a ceiling bulging with water explains why that needs attention at once.

Keeping your feet on the ground is enough to judge how a cover is holding up. After any strong wind and after heavy rain, look from the garden or the pavement with binoculars if you have them.

Look for flapping or billowing, edges that have lifted, a timber batten that has shifted and any pockets where water is sitting. Check the gutter and the ground below for fragments of plastic or screws. Inside, study the ceiling under the covered area, and check the loft hatch for drips or a damp smell.

Photograph anything that has changed and send it to the roofer who fitted it. Do not climb up to retighten a cover, and do not reach out of a window to pull it back into place. A tarp that has come loose can drag you with it, and a wet roof gives no grip.

Home policies commonly ask you to act sensibly to limit the damage, and leaving a failing cover on a roof for a long period may work against that. If the damage grows because the repair was put off, an insurer may argue that the extra loss was avoidable. Policies differ, so read yours and talk to your insurer about timing.

Receipts for the original cover matter, and so do photographs taken before it went on. Our page on insurance and temporary repairs covers the paperwork side in more detail.

If the problem came from a neighbour's roof or tree, the position is more complicated again, and our page on damage from a neighbour's tiles looks at who is responsible.

The sooner you book a survey, the shorter the tarp needs to survive. Ask the roofer to look under the cover when they come, because they can then see the state of the underlay, the rafters and the battens, which cannot be judged from outside. A moisture reading on the timbers and a photograph of each sound or rotten section go into the written report. Finding rotten timber at this stage is far better than finding it when tiles are going back on.

Materials may need ordering, particularly for old clay tiles, slates or a particular profile, and good weather is needed for the work itself. That is why a firm date matters even when the repair is not urgent. Be wary of anyone who knocks on your door and offers to remove the cover and fix the roof on the spot, which our page on storm chasing callers describes.

If you ring us about a leaking roof, our priority is to stop the water and make the property safe. After that we survey the damage, take photographs of your roof and put the permanent work into a written quote. If the fault needs only a small repair, the quote says exactly that, and the finished work carries a 10-year workmanship guarantee on paper. We also sweep up and carry the rubbish off when we go.

You will find more about how we handle urgent jobs on our emergency roof repairs page.