The short answer
Cleaning does not automatically void a home insurance policy or a covering manufacturer guarantee, but the wording of each decides. Damage caused by a harsh method, such as high-pressure washing on fragile tiles, may not be covered and may fall outside a guarantee. Check your policy and any guarantee first, keep photographs from before and after, and get the method agreed in writing.
Two different documents, two different questions
People often lump insurance and guarantees together, but they answer different questions. Your buildings insurance pays for damage from the events it lists, such as storm or fire, subject to exclusions. A guarantee on a covering, or on earlier roofing work, is a promise from the maker or the contractor about the product or the workmanship.
Neither document is likely to say that cleaning a roof is forbidden, which is reassuring but not the whole picture. What they do say, in different ways, is that damage from wear and tear, poor maintenance or unsuitable treatment is not covered. Cleaning sits awkwardly across those lines. Done well, it counts as maintenance and is helpful. Done badly, it can be the cause of the damage you later want to claim for.
So the useful move is to find both documents, read the relevant clauses and keep copies with your records. If anything is unclear, ask the insurer or the maker in writing before the work and keep the reply. Our page on roof cleaning and moss removal describes methods that are gentle enough for most coverings.
What insurers look at
An insurer deciding on a roof claim is asking what caused the damage. Storm damage is usually the insured event. A number of insurers define a storm as gusts of 55 mph or more, and standard cover can leave out gradual deterioration, including rain that gets in because a roof was poorly maintained. In November 2025 Which? reported FCA figures showing that just 32 per cent of storm claims made in 2024 ended in a payout (Which?).
That context matters for cleaning. A roof that is clean, sound and visibly maintained is easier to defend as a roof in good order. A roof that was power-washed, with tiles cracked or laps driven open, hands the insurer an argument that the damage came from the work and not the weather.
None of this predicts whether a claim would succeed, because each is judged on its own facts, and dealing with insurers is your side of the job. What we can add is a clear record of the roof before and after the work, which is useful to whoever reads it later, and we are glad to supply extra photographs on request.
How the method can matter
The riskiest approach for both insurance and guarantees is anything that damages the surface. High-pressure water can strip the face from concrete tiles, chip slate edges, loosen mortar at the ridge and force water under the laps into the loft. Damage like that is easy to trace back to the cleaning, so it may be treated as caused by the work and not by weather or age.
Gentler methods lower that risk. Moss lifted by hand, followed by a low-pressure soft wash and a biocide, leaves the covering intact and the laps undisturbed. Our pages on soft washing roofs and pressure washing a roof compare the two, and the guide to roof coatings covers a related treatment that also deserves a careful read of the small print.
Chemical treatment deserves a mention as well. Some manufacturers specify what may be used on their product. If you hold a manufacturer guarantee, ask what it says about biocides and cleaning agents before the day.
What to check before work starts
A short checklist protects you in most situations.
- Find your buildings insurance schedule and look for clauses on maintenance, wear and tear and unsuitable work.
- If a guarantee exists, on the tiles, a previous re-roof or a coating, read what it says about cleaning and who may carry it out.
- Ask the roofer which method will be used on your covering, and why.
- Ask for the method and the price in writing before any work.
- Take dated photographs of each slope yourself, or ask for them as part of the survey.
If you are unsure whether a guarantee stays valid after cleaning, contact the maker or the firm that gave it. Do not assume the answer either way.
Where a coating has been applied, or is being considered, there is a separate question about how lenders and surveyors see it. Our page on roof coatings and mortgage valuations picks that up.
How we work, and what you receive
We survey the roof before quoting, and the visit produces pictures of your slopes. That gives you a dated record of the starting condition, including any cracked or slipped tiles that were already there. The quote that follows is one fixed price in writing, and it names the method we propose for your covering.
After the clean, you receive photographs of the finished roof, and anything we found along the way is listed, whether it is a lifted flashing, a blocked outlet or a failing tile. Where a repair is needed, it is quoted separately and we do it only if you agree. Our own work carries a written 10-year workmanship guarantee. It is a promise about our workmanship only, with no insurer behind it, so it sits beside your policy and never stands in for it.
Timing can matter too. If a storm has already damaged the roof, arrange the claim and the repair first, then deal with cleaning. Cleaning in winter is possible, but a damaged roof comes before a dirty one.
