How to Choose a Roof Cleaning Company

The short answer: check insurance, ask which method the firm will use, and get a written fixed-price quote. Then ask for the guarantee in writing, and compare at least three firms. The checklist below covers the rest, so you can spot a poor offer before you sign.

1. The 8 questions to ask every company

Before you book, get answers to these eight questions, in writing if you can. A good firm will answer them happily, because clear answers help it win your trust.

1. Are you insured, and can you send me the certificates?
   Ask to see current certificates, and check that the cover includes chemical cleaning work. Treatment run-off can stain driveways, patios and plants if the work is careless.
2. Which method will you use, and what is the product?
   Ask for the method and the name of the biocide, so you can check its label and safety data sheet. "Soft pressure" or "gentle washing" on its own does not tell you what treats the growth.
3. Will you give me a written, fixed-price quote?
   A firm that will not commit to a written price before the work starts is a red flag. The quote should also say what it covers, such as biocide treatment, gutter clearance, debris removal and a photo report.
4. Do you offer a written guarantee, and for how long?
   Ask for the length, what counts as regrowth and how to make a claim. Get the terms in writing, because a spoken promise is hard to enforce.
5. How long will the job take?
   A careful job includes a survey, set-up, treatment, gutter clearance and tidying. Therefore, a very short visit should prompt questions about what the firm actually does.
6. Will you walk on my tiles?
   The National Federation of Roofing Contractors (NFRC) warns that unnecessary foot traffic often leads to cracked or broken tiles. Ask how the firm will reach the roof, and why.
7. What happens to the debris?
   Moss and gutter waste should leave with the firm, not stay on your drive or in your beds. Firms that carry waste as a business generally need to be registered waste carriers, according to GOV.UK, and you can check the Environment Agency's public register.
8. Can you show me recent local work?
   A firm with a real record in your area can show before and after photos of similar roofs. Ask for specifics, not just "we cover Kent".

2. Red flags to walk away from

• No written quote. Verbal-only pricing makes it easy for the figure to change on the day.
• A knock at the door. The NFRC cautions the public against doorstep sellers who offer moss removal followed by roof painting.
• Big claims about roof life. The NFRC says to treat claims about extended roof life or thermal efficiency with extreme caution unless credible UK third-party accreditation backs them.
• Pressure to start today. A firm that can start tomorrow with no survey has not looked at your tiles or your drainage.
• No mention of the method. If you cannot find out what will touch your roof, do not book.
• Insurance "to follow". If a firm will not show a certificate before the work, treat that as a no.

3. What insurance to ask about

Roof cleaning means working at height, with chemicals, close to neighbouring property. For that reason, ask each firm about the cover it holds. Then check what that cover includes, since policies differ.

• Public liability insurance covers damage or injury to other people and their property, so ask for the certificate and the limit
• Check the cover includes chemical application or exterior cleaning, because some policies exclude certain work
• Check the certificate is current, and note the expiry date
• Employers' liability insurance is a legal requirement once a business employs staff, with at least £5 million of cover, according to GOV.UK

If the firm is a sole trader, the same questions apply. Being small is a reason to check the cover more closely, not less.

4. Getting quotes that compare fairly

The NFRC advises getting at least three quotes. To compare them fairly, ask each firm to list what the price covers. A low quote may leave out the following items.

• Gutter clearance
• Debris removal and disposal
• A before and after photo report
• The biocide itself, if the quote covers labour only
• A written guarantee

A higher quote that includes all of these can be better value than a lower one that leaves them out, because you would pay for the missing items later. Our roof cleaning cost guide explains what drives the price, and our post on whether roof cleaning needs scaffolding covers a common extra.

5. Understanding guarantees

A softwash guarantee should cover regrowth of moss and algae. However, it will not cover colour changes in the tile, or structural problems. Guarantee lengths vary, so we do not claim any length is standard.

• Ask for the guarantee in writing, naming the property address and the treatment date
• Understand what triggers a claim, such as photographs of visible regrowth
• Ask whether it passes to a new owner if you sell
• Ask what the firm does if the roof needs re-treating

Our own is 5-year regrowth protection, in writing. If the roof needs re-treatment within that period, we re-treat it free of charge. Remember that conditions such as shade and damp affect regrowth, so a guarantee is only as good as its terms. Therefore, read the small print before you sign.

6. How to read online reviews

Reviews are useful, but they need critical reading, because some people post them to order. Signs of genuine reviews include the following.

• The reviewer names a place or street, not just the county
• Reviews are spread over a long period, not posted in one burst
• The reviewer mentions details of the job and what pleased them
• The firm replies to good and bad reviews alike

Signs of fake or incentivised reviews include a run of short five-star posts with no detail, or reviewers with only one review. Also check that the roof types match yours, and read whether softwashing is safe for roof tiles if you are unsure about your tiles.

7. Frequently asked questions