How to choose a mould removal company: questions to ask and red flags

Updated 6 November 2026 · By the Mould Cleaning team

Short answer: A good mould removal company cleans and treats the growth with fungicidal products, replaces affected sealant and finishes where needed, and tells you plainly what caused the mould and how to stop it. Ask what products they use, whether the cause will be identified, what is included in the price and what aftercare advice is given. Be wary of anyone who only sprays or fogs, sells damp-proofing for condensation mould or will not explain the cause.

What a proper mould job should include

Mould removal is a straightforward trade in principle, but quality varies a lot. The difference between a clean that lasts and one that fails within weeks is usually down to preparation, the treatment used and whether anyone looked at the cause. Before comparing prices, make sure each quote covers the same scope.

An inspection of every affected area, not just the one you pointed at
Protection of floors and furniture and containment of the work area
Physical cleaning of the growth with a fungicidal treatment, not just spraying
Treatment of the surrounding surfaces where spores will have settled
Replacement of mouldy silicone rather than sealing over it
A clear statement of the likely cause, with moisture readings if relevant
Practical advice on preventing regrowth and any repairs needed

Anti-mould painting is often quoted separately. That is fine, as long as you know whether the room will be left cleaned but stained, or fully finished.

Questions to ask before you book

Question	What a good answer sounds like
What product will you use?	A named fungicidal or biocidal mould treatment suited to the surface, used to manufacturer instructions
How will you stop spores spreading?	Wet cleaning methods, closed doors and protected surfaces, with no dry brushing or sanding of live mould
What do you think is causing it?	A specific, evidence-based answer such as condensation on a cold wall, a weak fan or a leak, not a guess
What is included in the price?	A clear list covering cleaning, treatment, sealant, painting, disposal and making good
What happens if the cause is damp, not condensation?	They say so and recommend a damp survey or the specific repair
How long will the room be out of use?	Hours for a clean, longer if painting or resealing needs drying time

A provider who answers these clearly, without jargon or pressure, is usually a provider who does the job properly.

Red flags to watch for

Recommending a chemical damp-proof course for mould that is plainly condensation
Fogging a room without physically cleaning the growth
Painting over mould without treating it first
Blaming the occupants immediately without checking fans, vents or heating
Pressure to sign on the day, or a price that drops sharply when you hesitate
No written quote, or a quote that just says mould treatment with no detail
Vague claims about guarantees with no explanation of what they cover

Fogging with a biocide can be a useful addition in some situations, for example after a flood, but on its own it does not remove dead mould, stains or the food source the mould was growing on.

Comparing quotes fairly

Cheap quotes often leave out the parts of the job that stop mould coming back, such as cutting out sealant, treating surrounding areas or painting with an anti-mould finish. Expensive quotes sometimes bundle in work you may not need, such as damp-proofing or replastering. Line the quotes up against the same list of work and ask each provider to explain any big differences.

Ask too whether the price is fixed for the agreed scope, and what would change it. Hidden issues, such as plasterboard that turns out to be rotten behind tiles, can come up, and a good provider will tell you in advance how that would be handled.

Landlords and agents: what to ask for

If you manage rented property, you also need evidence. Ask for dated before and after photos, a list of rooms and areas treated, moisture readings where taken, and a written note of the likely cause and recommended repairs. That record helps show the problem was investigated and acted on, which matters under repair duties, the Housing Health and Safety Rating System and, for social landlords in England, Awaab's Law.

Dated photos of each area before and after
Written summary of cause and work done
Recommended repairs listed separately from cleaning
Advice given to the tenant, recorded in writing

When to look for a damp specialist instead

Mould cleaning companies are the right call for condensation mould and for clearing mould after a cause has been fixed. If the signs point to rising damp, penetrating damp or a hidden leak, you need a building repair first. In that case look for an independent damp surveyor who explains the evidence and the full range of fixes, including simple ones such as clearing gutters or lowering ground levels, rather than one who leads with injection treatments.