The question usually arrives in one of two forms. The first is practical: the stain is small, the bucket is catching it, and it is a long way down the list of jobs. The second is financial: a repair costs money, and the temptation is to wait for a dry spell or for a quieter month. Both are understandable, and both underrate what a leak does while nobody is looking.
The short answer is that nobody can name a number of days a leak can be left, because the rate of damage depends on how much water comes in and what it meets. What can be said is that a leak does not stand still. Water moves along timbers, soaks insulation and finds its way down to ceilings, and the longer it runs, the more of the roof it touches. A fix that would have been a small job can become a large one.
This post is about urgency. It does not deal with whether a ceiling might come down, which is covered in our post on whether a leak can cause a roof collapse, or with the first steps, which are set out in what to do first when a roof leaks in Farnborough. Here we look at the cost of waiting, including the effect on insurance. You can find our approach to repairs on the roof repairs page.
Why there is no safe waiting time
A roof leak is not a fixed amount of damage that sits there waiting. It is a process, and the process continues every time it rains.
The variables
How fast damage builds turns on how big the opening is, how often rain reaches it, how much water gets through and where it goes. A pinhole in a flashing that drips only in driving rain is a different case from a missing tile over a bedroom that lets in water every time it is wet. Both are leaks, and neither can be dated for you from the ground.
Why small leaks fool people
A small stain on a ceiling is the visible end of what is often a larger path. Water can run along a rafter or across the top of a ceiling before it appears, so the stain may be some distance from the hole. By the time a mark shows, the insulation above it may already be wet.
Weather makes it worse
The Met Office averages for South Farnborough, covering 1991 to 2020, show 118 wet days in a typical year and around 53 air-frost days. Wet spells keep a leak topped up, and frost can widen a gap that water has found. Waiting for a dry spell is a plan that often runs out of dry days.
The practical rule
Treat a leak as something to deal with soon. Make it safe now, photograph it and get it looked at. A temporary measure buys time, but it does not replace finding the cause.
What a leak does while you wait
Damage from a leak builds in layers, and each layer adds to the eventual bill.
Insulation
Wet insulation stops doing its job and can sag or slump. It holds water against timber and ceiling, and drying it out is not always possible, so it may need replacing.
Timber
Rafters, battens, joists and the decking under a flat roof are designed to stay dry. Repeated wetting lets wood start to rot, and rotten wood is weaker and dearer to put right. Approved Document C asks for roofs that moisture cannot damage structurally, which shows how seriously the regulations treat the point.
Ceilings and decoration
Stains, blistering paint and soft plaster are the visible signs. A ceiling that has taken a lot of water may need replacing, and it can be dangerous if it is holding water.
Damp and mould
A damp area inside a house can encourage mould on walls and ceilings, which is unpleasant and can affect living conditions. Fixing the roof is the first step, and the room then needs to dry out.
Electrics and contents
Water near light fittings and sockets is a risk. Stock, furniture and belongings are at risk too, and the longer a leak runs, the more is likely to be damaged.
None of this is inevitable from the first drip. It is the reason the sensible approach is to act early, while the repair is small.
How delay can affect an insurance claim
Insurance is where waiting can cost the most, because a policy covers some kinds of damage and not others.
The Ombudsman's approach
When roof damage is blamed on weather, the Financial Ombudsman Service tests three things: did a storm happen, does the damage look like storm damage, and did the storm do the harm. It points out that wear, tear and slow deterioration are standard exclusions. Its stance is cooler when the roof was in a poor state beforehand and the owner was aware, or when bad weather simply brought an old fault to light. A leak ignored for months and claimed for after a rough night follows that pattern.
The policy defines its own storm
The Ombudsman's general picture of a storm is violent wind, usually accompanied by rain, hail or snow, with exceptional rain or snowfall alone able to qualify. What counts for your cover is the wording of your own policy, so read that rather than rely on a general idea.
Habits that help
Tell the insurer first, limit further damage with a temporary repair, and hold on to receipts. Dated photographs of the leak, the ceiling and the roof are the most useful single record, since the Institution of Structural Engineers calls them vital evidence of what happened. Take them as soon as it is safe to do so.
No promises
Nobody can promise that a claim will succeed. A prompt report and good evidence help, but the insurer decides under the terms of the policy. If you disagree with the outcome, the Financial Ombudsman Service helpline is 0800 023 4567, and its service is free.
Temporary measures and their limits
Holding the situation while a proper repair is arranged is sensible. It is also a risk, because a temporary fix can make a leak look solved when it is not.
What counts as temporary
A tarpaulin secured over a damaged area, a patch over a split, a bucket under a drip and a sheet over stored goods are all measures that limit damage for a short time. Making a leaking roof safe is the first job, and a proper repair follows once the cause is known. Our guide to temporary roof repair covers what is realistic.
The risks of doing it yourself
Going on a roof is dangerous, and a wet roof is slippery. Do not climb up to fix a tarpaulin. Work from the ground or from inside, and leave the roof work to someone equipped to do it. If water is coming in near electrics, keep clear and have the circuit checked.
Do not stop at the patch
A temporary measure that works well can lead to a decision to wait. It is worth setting a date for the proper repair at the same time, so that the patch does not become the plan.
Photographs
Take dated photographs before and after the temporary measure, with a wider shot that shows where on the building the damage sits. They are useful for the insurer and for the roofer who will do the repair, since they show what the roof looked like at the start.
Slow and intermittent leaks
Not every leak shows itself every time it rains. Intermittent leaks are the ones most easily put off, and often the ones that run longest.
Why they are harder
A leak that only appears in particular wind directions or after heavy rain can be difficult to trace, because it is dry when someone comes to look. The path can be indirect, and the cause may be a flashing, a valley, a cracked tile or a blocked outlet some way from the stain.
Keep a log
A simple record helps: the date, the weather, where the water appeared and a photograph. It gives a roofer something to work from and shows the insurer how the problem developed. Our guide to finding a roof leak explains how the trace is done.
Condensation is not always a leak
Moisture on timbers or on the inside of a roof can be condensation, not water coming through a hole. BS 5250 covers moisture in buildings, and Approved Document C expects roofs not to be harmed by interstitial condensation. A survey can tell the two apart, which matters because the cure differs.
Do not wait for it to get worse
A leak that is intermittent today may be continuous tomorrow. If you have seen a stain, ask for the roof to be checked, rather than waiting for proof. A roof that has been dry for three weeks has not repaired itself, and the next heavy shower will find the same opening.
What it costs, and getting it looked at
Cost is a common reason leaks are left, so it is worth setting out what the published guides give. Treat them as national ballparks; your own roof is priced in writing after a survey.
Published figures
MyJobQuote puts the average roof repair at around £650 in 2026 (updated 6 October 2026). It says emergency call-out charges typically range from £150 to £300, and extensive storm repairs can cost £1,200 or more (updated 22 October 2026). Those are national figures and each job depends on the cause.
The comparison that matters
A repair done early can be a fraction of the cost of one done after the leak has spread to timber, insulation and ceilings. A leak left for a long time can grow a small repair into a large job.
What the survey does
The surveyor traces the source and checks the surroundings for damage, recording photographs and measurements, and the findings come in writing with one price for the repair. A repair is priced as a repair, and the question of a re-roof arises only if the photographs show one is justified.
Next step
If there is a leak now, make it safe, photograph it and arrange a survey. The sooner the cause is known, the smaller the job is likely to be. For a leak that has already damaged a ceiling, our post on collapse risk explains the signs to watch.
