How to Remove Mould in the Shower (and Stop It Coming Back)

Why the shower is a mould magnet

Mould needs moisture, food and time, and a shower provides all three. After you shower, droplets sit in the grout, humidity briefly hits 80–100 %, and soap and skin residue act as food. If the room doesn’t dry out within a few hours, airborne spores (which are everywhere) start to grow.

Typical causes:

• Poor ventilation, for example a window left on the latch that chills the walls but hardly exchanges any air.
• Windowless bathrooms with an extractor fan that switches off too soon.
• Standing water in corners, on shelves and behind bottles.
• Old or damaged sealant that lets water underneath.
• Cold external walls where moisture condenses.

Tell the difference between surface mould on tiles and grout, which you can tackle yourself, and mould that comes from inside the wall (patches behind tiles, on plaster or the ceiling). The second kind usually points to a leak or a structural problem.

Step by step: removing shower mould

1. Prepare

Open the window and put on gloves. Move bottles, the curtain and the mat out of the way. If you recently cleaned with a descaler or vinegar, rinse everything thoroughly with water first so nothing can react with bleach.

2. Treat tiles and grout

Option A – bleach spray (heavier growth): Spray directly onto the patches from 10–20 cm away. Don’t fog the whole room. Leave it for the time stated on the label, then rinse well. Repeat on stubborn spots.

Option B – alcohol (delicate surfaces, light growth): 70–80 % isopropyl alcohol or ethanol kills mould without bleaching. It is good for wood, window frames or near natural stone. Apply with a cloth, wipe, then throw the cloth away. Keep it away from flames.

Tip: An old toothbrush is great for grout lines. Work with the product applied, not dry, so you don’t spread spores.

3. Check the sealant: save it or replace it?

If the stains are gone after two treatments, you’re done. If grey or black dots remain, the mould is inside the silicone and the bead needs replacing. It takes about an hour:

1. Cut along both edges of the old sealant with a utility knife and pull it out.
2. Remove all residue with a plastic scraper or a sealant remover.
3. Clean the joint with alcohol and let it dry completely, ideally overnight.
4. Mask both edges with tape and run a smooth bead of new sanitary silicone.
5. Smooth it with a tool or a finger dipped in soapy water, then pull the tape straight away.
6. Don’t shower for about 24 hours.

4. Fix the cause

Without tackling the moisture, the mould will be back within weeks. A cheap hygrometer tells you quickly if your ventilation works: humidity should fall below 60 % within roughly 30–60 minutes after a shower.

What not to do

• Mix cleaners. Bleach plus acid makes chlorine gas.
• Seal over old sealant. New silicone on mouldy silicone won’t bond and the mould grows through.
• Rely on tea tree oil. The evidence is weak, and essential oils can irritate the airways.
• Dry-brush mould. This spreads spores into the air.

When to call in help

Get professional help if the area is larger than about 0.5 m², the mould is behind tiles or in the masonry, there’s a musty smell with no visible cause, or it keeps returning despite good ventilation. If you rent, tell your landlord in writing. Structural causes are their responsibility.