How to Remove Mould From a Bathroom (and Stop It Coming Back)

Safety First

Mould is unpleasant and can irritate lungs, skin, and allergies, so treat the cleaning like a proper job, not a quick wipe. Wear rubber gloves, open a window, and switch the extractor fan on before you start. If you have asthma or a breathing condition, wear a mask, and keep children and pets out of the room while you work.

Never mix cleaning products. In particular, never mix bleach with vinegar, or bleach with any other cleaner — the combination creates harmful fumes. Choose one cleaner for the job and stick to it. White vinegar and dilute bleach both kill mould, but they are alternatives, not partners.

If the mould covers a large area — more than about a square metre — or it keeps coming back after proper cleaning, stop and read the last section of this guide. That is the point where the cause is probably a leak or a ventilation failure, and cleaning alone will not fix it.

What You Need

You need very little: rubber gloves, a spray bottle, white vinegar or a dilute bleach solution (one part bleach to ten parts water), an old toothbrush or a small stiff brush, cloths, and a bucket of warm water. A step stool helps for ceilings, and a squeegee is useful for the prevention routine later.

White vinegar is the gentler option and works well on light mould. Dilute bleach is stronger and better for stubborn black mould on grout, but it can damage coloured grout and fabrics, so test it on a hidden spot first and never use it on natural stone. Pick one, not both.

Do not buy a special “mould remover” unless you want to — they are usually just dilute bleach in a spray bottle at several times the price. The cleaning matters far more than the brand.

Clean the Grout and Sealant

Start with the grout lines and the sealant around the bath and shower, where mould is worst. Spray your chosen cleaner onto the mould and leave it for 15 minutes — the waiting is the work, because the cleaner needs time to kill the mould rather than just wetting it.

Scrub with the toothbrush along the grout lines and into the corners. Rinse with clean water and dry the area with a cloth. If black staining remains in the grout after scrubbing, it may be staining rather than live mould — the mould is dead, but the colour has soaked into the grout. Staining alone is not a health problem, but it looks bad, and it means the grout is porous enough to grow mould again.

If the sealant itself is black through, or peeling and cracked, cleaning will not save it — it needs replacing, which is covered in the section below.

Clean Walls and Ceilings

For walls and ceilings, spray the cleaner onto a cloth rather than spraying the wall — it gives you control and stops cleaner running into your eyes. Wipe the mouldy area in sections, rinsing the cloth often, and work from the edges of the patch inwards so you do not spread it.

On a ceiling, use a mop or a cloth on a long handle, and wear eye protection if you are looking up while cleaning. Take your time: mould on a ceiling is usually a sign of steam collecting there, and the area may be larger than it first looks.

Dry everything afterwards. Mould loves damp, and a surface left wet after cleaning will grow it back faster than a surface that was never cleaned. Open the window, run the fan, and wipe the tiles dry with a clean towel.

When Sealant Has to Be Replaced

Sealant that is black through, cracked, peeling, or coming away from the bath or tiles cannot be cleaned back to health. The mould is growing underneath it, and no amount of scrubbing reaches it. Replacing it is a straightforward job: cut the old sealant out with a sharp knife or a sealant remover tool, clean the gap, let it dry fully, and apply new bathroom sealant in a smooth bead.

Let the new sealant cure for 24 hours before you use the shower or bath, and keep the room ventilated while it dries. If you are not confident doing this yourself, a handyman or plumber will do it quickly and cheaply — it is a common small job, and a bad seal causes leaks, so it is worth doing properly.

While the sealant is out, look at the wall behind it. If the wall is soft, crumbling, or smells damp, there may be a leak behind the tiles, and that is a job for a professional rather than a tube of sealant.

Fix the Moisture — the Real Cure

Cleaning removes the mould you can see. Fixing the moisture stops it coming back, and this is the part most people skip. A bathroom produces litres of steam every day, and if that steam has nowhere to go, it condenses on the coldest surfaces — usually the ceiling and the outside wall — and mould follows.

Run the extractor fan during every shower and for 20 minutes afterwards. If you do not have a fan, open a window a little while you shower. After a bath or shower, open the bathroom door and a window to let the steam out, rather than letting it sit in a closed room.

Wipe the tiles and the shower screen with a squeegee after use — it takes 30 seconds and removes most of the water that would otherwise evaporate into the room. Keep the room warm enough that surfaces do not stay cold and damp, and fix any dripping tap or leaking pipe, because a constant drip feeds mould all day and night.

A Prevention Routine That Takes Minutes

Once the bathroom is clean, a short routine keeps it that way. After each shower: squeegee the tiles and screen, leave the fan on for 20 minutes, and leave the door ajar. Once a week: wipe the grout lines and the sealant with a cloth, and check the corners and the ceiling for the first specks of mould — catching it early means a wipe, not a deep clean.

Once a month: check the sealant for cracks, check under the sink for leaks, and give the extractor fan grille a wipe, because a clogged fan moves far less air. A fan that sounds loud but moves little air is often just dirty.

The routine sounds like a lot written down, but in practice it is about two minutes a day. The alternative — a full mould clean every few months — takes far longer.

When to Call a Professional

Call a professional if the mould covers a large area, if it returns within weeks of a proper clean and a fixed routine, if there is a damp smell you cannot trace, or if the wall or ceiling feels soft or crumbling. These are signs of a hidden leak, a failed waterproofing layer, or a ventilation problem that cleaning cannot solve.

Also call someone if anyone in the household has a serious breathing condition and the mould is extensive — in that case, do not attempt a large clean yourself. A specialist mould remover can clean safely and find the source, and a plumber can trace a leak that you cannot see.

Get more than one quote if the job is large, and ask the professional to explain the cause, not just the price. A fix that does not address the cause is money wasted — the mould will be back within months.

Questions People Ask

Is bathroom mould dangerous?

Small amounts are mostly a nuisance, but mould can irritate eyes, skin, and lungs, especially for people with asthma or allergies. Large amounts, or mould in a bedroom where you sleep, should be dealt with promptly. If anyone in the household has breathing problems, take it seriously and get advice early.

Does vinegar kill mould?

Yes, white vinegar kills most common bathroom mould on hard surfaces. Spray it undiluted, leave it for an hour, scrub, and rinse. It is gentler than bleach and safe on coloured grout, but for deep black mould on white grout, dilute bleach is usually more effective.

Why does it keep coming back?

Because the moisture that feeds it has not been fixed. Cleaning removes the mould; ventilation, heat, and leak repair remove the conditions it needs. If it returns within weeks of a thorough clean, the cause is moisture, not cleaning — check the fan, the window habit, and for leaks.

Can I paint over mould?

No — not until the mould is killed and the surface is dry. Paint over live mould will peel, and the mould will grow through it. Clean first, let it dry fully, use a mould-resistant primer if the area is prone to damp, and only then paint.

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