Professional mould cleaning: how long it takes and what to expect on the day

Updated 6 November 2026 · By the Mould Cleaning team

Short answer: A professional mould clean of a single room or bathroom usually takes two to four hours. The technician inspects and measures the mould, protects the room, cleans and treats the affected areas with a fungicidal product, and replaces sealant if needed. Jobs including anti-mould painting or several rooms usually take one to two days to allow for drying between coats.

Typical timings

Job	Typical time on site
Single wall or window reveal	1 to 2 hours
One room, cleaning and treatment	2 to 4 hours
Bathroom clean with resealing	3 to 5 hours, plus around 24 hours for sealant to cure
Room cleaned and painted with anti-mould paint	1 to 2 days including drying time
Several rooms or whole house	1 to 3 days depending on extent

These are typical guide timings. Heavily affected rooms, high ceilings and work that needs wallpaper stripping or plaster repairs take longer.

Before the visit: how to prepare

Move small furniture, ornaments and bedding away from affected walls if you can
Take clothes out of wardrobes standing against mouldy walls
Note when the mould is worst and where washing is usually dried
Find out whether extractor fans have a run-on timer and when they were last cleaned
Arrange for anyone with asthma or a lung condition to be out of the room during the work
Make sure pets are kept away from the work area

Avoid cleaning or painting over the mould in the days before the visit. Seeing it as it is helps the technician judge its pattern and cause.

What happens on the day

The technician starts by looking at each affected area, measuring it and, where useful, taking moisture and humidity readings. This confirms whether you are dealing with condensation or something else, and avoids treating a damp wall as a cleaning job.

Next the room is prepared. Floors and nearby furniture are covered, doors to the rest of the home are kept closed, and windows are opened where possible. Mould is then cleaned using wet methods with a fungicidal treatment, left for the required contact time and wiped or rinsed away. The surrounding surfaces are treated too, because spores and early growth are often present beyond the visible patch.

Where silicone is mouldy, it is cut out, the joint is cleaned and dried and new fungicidal sealant applied. Heavily affected wallpaper or flaking paint is stripped back. Waste is bagged and removed.

Smell, noise and disruption

Most mould treatments have a noticeable smell while wet that fades as the room is aired. Noise is limited to scraping and occasional power tools if paint or wallpaper needs taking back. You can usually stay in the home while the work happens, using other rooms. Keep children and pets out of the treated room until it has dried and been aired, typically a few hours.

Afterwards: aftercare for the first few weeks

Air the room well for the rest of the day
Leave new silicone untouched and dry for around 24 hours, or as advised
Do not hang pictures or push furniture back tight against treated walls
Run extractor fans during and after every shower and while cooking
Keep trickle vents open and heat the room steadily rather than in short bursts
Wipe condensation from windows each morning
Watch the treated area and report any early regrowth

If anti-mould painting is planned as a separate visit, the treated surface must be fully dry first. On plaster that has been wet this may take a few days.

What you should receive

At the end of the job you should know what was cleaned and treated, what caused the mould, and what to change. Landlords and agents should also expect dated before and after photos and a short written summary. If a repair such as a new extractor fan, a gutter repair or loft insulation is needed, it should be named clearly so it can be arranged.

A list of the rooms and areas cleaned and treated
Whether sealant was replaced and when it can be used
The likely cause, with any moisture or humidity readings taken
Recommended repairs, listed separately from the cleaning
Simple prevention steps for everyone living in the home

Keep this alongside your photos. If mould does reappear, it gives whoever looks at it next a clear starting point, and in rented homes it forms part of the record that the problem was investigated and dealt with.

When the job takes longer than planned

Most mould cleans finish on the day, but a few things can extend the work. Wallpaper that comes away to reveal blown or crumbling plaster, plasterboard that turns out to be soft behind tiles, or mould found in a second room once furniture is moved all change the scope. So does finding that the surface is damp from a leak rather than condensation, in which case cleaning should pause until the cause is fixed. A good provider stops and explains what they have found, what it would cost to deal with, and what the options are, rather than carrying on and adding to the bill without discussion.