Damp and mould in the bathroom
A 10-minute shower puts more water into the air than a bathroom can lose on its own — especially without a window. Most cases are steam with nowhere to go; sometimes it is a hidden leak.
What it usually is
Mould in the grout, the silicone and on the ceiling above the shower, a mirror that stays misted long after the shower.
A patch that grows in dry weather, near the floor or on the wall on the other side, a water meter that turns with all taps closed.
A patch with an outline on the ceiling, below the neighbour's bathroom.
What to check
- How long the mirror stays misted after a shower (more than 20–30 min = weak extraction).
- Whether the extractor pulls: hold a sheet of paper against the grille with it on.
- Whether there are patches outside the bathroom, on the adjoining wall.
- Whether the water meter turns with every tap closed for 10 minutes.
What you can do today
- 01Leave the extractor on for 15–20 minutes after each shower (or fit a timer).
- 02Squeegee the walls and the screen after showering.
- 03Leave a 1–2 cm gap under the door so air can come in.
- 04Clean the grout with diluted bleach and replace the silicone when it is black inside.
Guides for this room
Frequently asked questions
As a rule of thumb, one that changes the bathroom air several times an hour, with a timer or humidistat so it keeps running after the shower. More than the power, what matters is that it vents outside and that air can come in under the door.
On the surface, yes. When the silicone is black inside, the mould has gone through it and the only fix is to remove it and apply new silicone on a fully dry surface.