How to Choose a Roof Cleaning Company

The short answer: Check insurance, confirm they use real biocide softwash (not pressure washing in disguise), ask for a written fixed-price quote, and demand a multi-year guarantee. The checklist below covers everything else.

1. The 8 questions to ask every company

Before you book any roof cleaning company, get answers to these eight questions — in writing if possible.

1. Are you insured, and can you send me the current certificate?
   Public liability insurance covering at least £1 million is non-negotiable. Softwash work can, if done incorrectly, cause staining to neighbouring driveways, patios, or vegetation. Verify the certificate is in-date and covers softwash or exterior cleaning specifically.
2. Do you use real biocide softwash or pressure washing?
   Ask specifically: "What active ingredient do you use, and at what concentration?" The honest answer is sodium hypochlorite (or a quaternary ammonium compound) at a stated dilution. "We use soft pressure" or "gentle washing" is not softwash — it is a rebadged pressure wash.
3. Will you provide a written, fixed-price quote before the job?
   Any company that can't or won't commit to a fixed price in writing before starting work is a red flag. The written quote should specify what's included: biocide treatment, gutter clearance, debris removal, photo report.
4. Do you offer a written guarantee on regrowth, and for how long?
   Reputable softwash operators offer a 4–5 year written guarantee against moss and algae regrowth. Ask for it in writing, and check it covers the specific treatment type for your roof.
5. How long will the job take?
   A real softwash on a standard semi-detached takes 3–5 hours, including setup, biocide application, gutter clearance, and debris removal. Any quote for a "softwash" that's done in under 90 minutes should raise serious questions.
6. Will you walk on the tiles?
   No reputable softwash operator needs to walk on your tiles. The work is done from ladder access with long-handled equipment. Walking on tiles risks cracking, dislodging and voiding the tile manufacturer warranty. If they say they'll walk on the roof, ask why.
7. What do you do with the debris?
   All moss debris, gutter contents, and waste material should be bagged and removed at the end of the job. Ask specifically — leaving debris on a driveway, in garden beds, or in downpipes is both unprofessional and a potential legal issue.
8. Can you provide references or show me recent local work?
   A company with a real track record in your area will have before/after photos, local customer references, and recent reviews naming specific neighbourhoods. Vague references to "work in Kent" or "customers in Surrey" without specifics should prompt follow-up questions.

2. Red flags to walk away from

• No written quote. Verbal-only pricing is how invoice inflation happens.
• Door-to-door cold call. Legitimate roof cleaning companies don't need to cold-call; they have enquiry pipelines. Cold-call offers are almost always pressure washing at inflated prices.
• Immediate availability. If they can start tomorrow with no survey, they're not surveying — and not assessing whether your roof needs scraping, what tile type it is, or whether there's structural damage that should be flagged.
• No mention of biocide. "Soft wash" without chemistry is not softwash. Ask for the product name.
• Price significantly under market rate. For a standard semi, anything under £200 for a claimed softwash is either pressure washing or an incomplete job (no gutter clearance, no debris removal, no guarantee).
• Can't produce insurance documentation. Any request for an insurance certificate that isn't fulfilled immediately — "I'll send it later," "my partner has it" — means the insurance either doesn't exist or doesn't cover the right work.

3. What insurance to require

At minimum, require:

• Public liability insurance — minimum £1m, preferably £2m+ for residential work
• Coverage must include chemical application or softwash/exterior cleaning — some basic PLI policies exclude chemical work
• Certificate must be current — ask for the expiry date and verify it
• Employer's liability insurance if they bring a team (legally required in the UK)

If a company operates as a sole trader, PLI is still required. "I'm just a one-man band" is not a reason to be uninsured — it's a reason to be doubly careful.

4. Getting quotes that compare fairly

When collecting multiple quotes, make sure you're comparing like-for-like. A low quote may exclude:

• Gutter clearance (standard with a proper softwash)
• Debris removal and disposal
• Before/after photo report
• The biocide itself (some quote the labour only)
• A written guarantee

Ask each company to itemise what's included. A £350 all-in quote with a 5-year guarantee and gutter clearance is better value than a £250 quote for biocide application only with no guarantee.

5. Understanding guarantees

A softwash guarantee covers regrowth of moss and algae — not cosmetic changes to tile colour or structural issues. Reasonable guarantee terms:

• 4–5 years is standard for professional softwash biocide treatment
• The guarantee should be in writing, naming the property address and the treatment date
• Understand what triggers a claim — most require photographic evidence of visible regrowth, not just a slight colour change
• Check whether the guarantee is transferable if you sell the property (some are, and this adds value at sale)

A 12-month guarantee on a "softwash" treatment is a tell that the treatment didn't use effective biocide chemistry — 12 months is barely longer than a pressure wash cycle.

6. How to read online reviews

Reviews are useful but require critical reading. Signs of genuine reviews:

• Reviewer names a specific location or street (not just the county)
• Reviews are spread across 2+ years, not clustered in one campaign
• Reviewer mentions specific details — job scope, crew name, what they were pleased about
• The company replies to both positive and negative reviews

Signs of fake or incentivised reviews: all 5 stars, no detail, all posted within weeks of each other, reviewer profiles with only one review.

7. Frequently asked questions

This guide is updated periodically. Last updated: 27 May 2026.