Mould despite extractor fan

[zaffa]

The extractor fan in our bathroom stopped working about a year ago. I finally got around to getting it replaced about four months ago, and ever since then I've noticed mould on our bathroom ceiling.

I'm really confused by this, isn't the fan supposed to stop mould? We keep the bathroom window open a lot, and run the fan with every shower, so I can't figure out why suddenly mould is growing over the ceiling?

We've cleaned it and repainted with anti mould paint but I don't know if it will reappear (we've cleaned it already a few times). Does existing mould encourage more mould?

We dont have a bathroom extractor fan. The walls have cavity wall insulation, would that make it difficult to fit a wall fan? Downstairs bathroom, ceiling fan is not on.

Good luck dealing with it. I moved to this bungalow and nine months later found out I had mould under every carpet, every floor had to be replaced. I still feel so guilty, I believe my late elderly dog had spores in his lungs, he started coughing months after we moved in.

CWI not a problem, unless you have polystyrene beads, which sometimes pour out. I suppose you could drill small holes first and inject expanding foam to stabilise it, but I have not tried.

Cutting the hole will disturb mineral wool, so you usually stuff wool into the cavity to form a collar round the plastic pipe that is used to line the wall.

We have the beads, unfortunately. When installed they forgot to sleeve an airbrick (not in bathroom) and we had to get them back to do it.

Thank you everyone (and glad to see lots of other people getting help too!) I do feel better that it's not just me with this issue!

DH is going to check out the loft this weekend, we might need to get more loft insulation

The answer is you now have additional moisture from your DSS …erm “taking long baths.”
Paint the ceiling with Zinsser and then dulux easycare or a bathroom paint.
Adjust the timer on your fan to run longer.

We have ours linked to the downstairs loo/shower room light, as there's no window in there. It starts when the light goes on, and stays on for a little while after the light goes off. If somepone has had a shower that's left it steamy, we just leave the light on a bit longer until it's all dry. We do squeegee down the shower walls/door after every shower, though, that gets rid of a lot of water down the drain that doesn't then need to be evaporated and removed.