The bathroom grout and tile guide

Bathrooms cop the worst of winter. Hot showers, closed doors and poor ventilation create the warm, damp environment soap scum and mould thrive in.

And the part everyone struggles with? Grout. Those lines go grey, then black, and no amount of spray-and-wipe seems to touch them. Here’s why, and what actually works.

First, understand why grout goes black

• Grout is porous, like a sponge.
• It soaks up soap residue, body oils and moisture.
• Mould sets up inside the pores, not just on the surface.

That’s why wiping does nothing — the staining is in the grout, not on it. You have to get into the pore.

Use the right tool: a stiff brush, not a cloth

• A cloth or sponge can’t reach into the texture of grout.
• A stiff grout brush or an old toothbrush is what moves the dirt out.
• This is the #1 reason people feel grout “won’t come clean” — wrong tool for the surface.

Use a paste that clings

Spray cleaners run straight off vertical grout lines before they can work. Instead:

1. Make a paste of bicarb soda and a little water.
2. Smear it along the grout line.
3. Spray white vinegar over the top — it’ll fizz, lifting grime out of the pores.
4. Leave 10 minutes, scrub, then rinse with warm water.

For stubborn floor grout, bicarb mixed with a little hydrogen peroxide is a step up.

Natural stone tiles (marble, travertine): skip the vinegar, the acid etches them. Use a pH-neutral, stone-safe cleaner instead.

Deal with soap scum separately

That cloudy film on glass and tiles is soap scum , soap residue plus minerals from your water.

• Spray on warm white vinegar and leave 5 minutes.
• Wipe with a microfibre cloth and buff dry.
• For shower glass, a quick squeegee after each shower is the real long-term fix — 30 seconds now saves an hour of scrubbing later.

Tackle the silicone seal

The flexible seal around the bath, basin and shower base is silicone, and once mould gets in, scrubbing often won’t shift it.

1. Lay a strip of toilet paper along the seal.
2. Soak it with white vinegar (or a mould-specific product).
3. Leave a few hours or overnight.
4. Remove and rinse.

If the silicone is still black afterwards, it’s perished and needs replacing, not cleaning.

Then keep it that way

• Run the exhaust fan for 15 minutes after every shower.
• Leave the door open so the room dries out.
• Hang towels where they can actually dry.
• Once grout is clean and dry, apply a grout sealer once a year to stop moisture and grime soaking back in.

When grout has gone permanently dark or silicone has perished no matter what you try, a professional clean or re-seal resets everything back to a clean baseline that’s far easier to maintain.