Mould or condensation in bathroom

[BS83]

Hi

This spot appeared overnight last night (following a v cold night). Nothing else anywhere else in the house including rooms which have the same external wall and under the loft.

There was a lot of condensation built up on all the windows in the house.

For info, the loft is above the bathroom and one other room (the other room was not affected) and the house is c 1930s.

I have also been told there’s a breach in the local water supply and the water company will be replacing the servicing pipes on the main road to the property (read somewhere about iron deposits)

Any thoughts on what it could be and likely remedies?

 

[freddiemercurystwin]

Been in the loft to check it's not a leak?

 

[BS83]

I haven’t yet as it’s not boarded and just waiting on someone to be here. Am I looking for just damp in the loft along the same wall?

 

[freddiemercurystwin]

Have you had any rain lately? A leak could be anywhere in the loft, water can track it's way across rafters, battens, across ceilings etc, not necessary just directly above the wet patches but obviously check the top of the plasterboard above the patch too. Not saying it is a leak but you should be able to at least eliminate that as a possible cause. Is the damp patch wet to the touch?

 

[BS83]

Thank you - that’s really helpful. We had weeks of rain but a couple of weeks ago and nothing happened in that time after.

It wasn’t wet to touch and I ran along the entire length and down the sides of the same wall and the next room to check and nothing was wet

It happened just overnight last night and the only difference this morning was the amount of condensation on all the upstairs windows including the bathroom which wasn’t used for a shower last night.

I’ve got the dehumidifier running now and will leave it to run.

I have cleaned it up with cleaner and the stain has gone for now.

If it’s not an obvious leak and the paint used it seems is very porous and not washable. What paint is best for bathrooms?