Mould in the bathroom: how to clean grout and sealant, and why the extractor fan matters

Mould in the bathroom comes back because the room stays damp, so cleaning it only works if you also remove the moisture. Scrub the grout and the silicone, replace the sealant if the mould is under it, clean the extractor fan and ventilate after every shower. Those four habits do more than any "anti-mould" spray.

Why the bathroom grows mould

Mould needs moisture, a surface to feed on and time. A bathroom gives it all three: steam from showers, soap film on tiles and a small room where air does not move. The black spots collect first where water sits longest: the grout lines, the silicone around the bath or shower tray, the bottom of the shower curtain and the corners of the ceiling.

Step 1: clean the grout

Grout is porous, so it holds water and dirt. Once a semester (every six months) it deserves a proper scrub:

1. Ventilate the room and wear gloves.
2. Apply a bathroom cleaner suited to tiles, or the product recommended for your tile type, and leave it for the time on the label.
3. Scrub the lines with a stiff brush or an old toothbrush, then rinse with clean water and dry.

Never mix bleach with vinegar, ammonia or other cleaners: the mixture releases toxic gas. Use one product at a time, with the window open. If the grout is crumbling or the tile sounds hollow, cleaning will not solve it: that needs repair.

Step 2: check the sealant

The silicone strip between the bath, the tiles and the shower tray keeps water out of the wall. If it is cracked, peeling or has black spots that do not come off with scrubbing, the mould is inside it or behind it. Surface cleaning is not enough: remove the old sealant and apply new silicone, usually about every two years, after drying the joint completely. It is a small job, but doing it over damp joints traps the water in. For why leaks in this spot matter, see our guide to preventing water damage at home.

Step 3: clean the extractor fan

An extractor fan that is clogged with dust moves little air, and then the humidity stays. Every six months, switch it off at the wall or breaker, remove the cover (many just clip or unscrew), wash the cover and wipe the visible blades. Test it afterwards: a sheet of toilet paper held against the grille should stick to it. Do not work on the wiring or open the housing; if the fan is noisy, weak or does not start, a qualified electrician should look at it.

Step 4: daily habits that stop it

• Run the fan, or open the window, during the shower and for 15 to 20 minutes after. The right time depends on the room; the goal is for the mirror to clear.
• Wipe the walls and the shower screen with a squeegee or a towel after use. It takes a minute.
• Spread out the shower curtain so it dries, and wash it every few months, or replace it if the mould is deep in the fabric.
• Leave the towels to dry outside the bathroom when you can.
• Fix drips: a dripping tap or a leaking seal adds moisture all day.

If you rent

Recurring mould is one of the most common sources of arguments between tenants and landlords. In general, ventilating and cleaning surfaces falls to the tenant, while defects in the building (leaks, a broken extractor, rising damp) are the owner's concern. This varies by country, region and lease, and this is not legal advice: check your contract and tell your landlord in writing, with photos. More in who is responsible for what when renting.

When to call a professional

Call someone if the mould keeps coming back after you have cleaned and ventilated, if it covers a large area, if the wall feels damp or the paint bubbles, or if you suspect a leak behind the tiles. People with asthma, allergies or weak immune systems should avoid cleaning large patches of mould themselves.

Make it a routine

Grout every six months, extractor fan every six months, sealant check once a year: it is easy to forget until the black spots appear. HouseKiper reminds you of each one at the right time. The full routine is in the complete home maintenance checklist and the apartment checklist.

How do I get rid of black mould in shower grout?

Ventilate, wear gloves and scrub the grout with a bathroom cleaner suited to your tiles and a stiff brush, then rinse and dry. Never mix bleach with other cleaners. If it returns quickly, the cause is damp, not dirt.

How often should I replace bathroom silicone?

Roughly every two years, or sooner if it cracks, peels or has mould that does not come off. Dry the joint fully before applying the new bead.

Does an extractor fan really prevent mould?

Yes, if it works and you use it. It removes the steam that mould feeds on. Clean it every six months and run it during and after showers.

Can I just paint over bathroom mould?

Not as a fix. Paint over active mould hides it while the damp keeps feeding it. Clean the surface and fix the source of moisture first.