Bathroom wall paint suddenly gone patchy

Hi all,

One of my bathroom walls is an external Victorian wall. It’s been damped checked etc. It was previously painted with matt emulsion with no problems, however I got same colour in Dulux bathroom paint and painted it in that in August.

It looked absolutely fine, until about 2 weeks ago, at the same time it seems the weather got substantially colder (might be irrelevant).

Now it appears patchy all over!

Matthew32, good evening.

Several questions [no real answers]

What is the affected wall made from? [brick? / masonry? / Lath and Plaster?]

If? cavity brick, does the cavity have retro-filled insulation?

The vent extractor? does it have a duct right through the wall? is the duct clear, IE. not blocked?

Sorry about the questions, any answers mat assist the board with giving "opinions" as to an answer.

Ken.

Hi Ken,

thanks for your reply. I’ve lived here 8 years and there’s never been this problem. It was painted in exactly the same colour in emulsion, but, back in August I painted in the same colour but in bathroom paint. It still looked absolutely fine until about 10 days ago, when it appeared like the photo.

It’s a solid double brick wall, Victorian that’s plastered.

The fan goes through the wall and isn’t blocked. It’s strange that it’s just suddenly appeared like this. The only thing I’ve changed is repainting it in bathroom paint.

This is how it’s looked until about 10 days ago in the image I’ve attached. Absolutely fine.

Matthew32, good evening, again.

Thoughts are possibly a chemical reaction between the paints??

I thought about some sort of "detergent" that was used to clean the wall leaving a residue, but the pattern is not consistent with this, such an event would tend to leave circular marks or vertical stripes?

The initial "knee jerk" diagnosis of the issue is rain water penetration / lack of ventilation / cold bridge. You have in effect eliminated all aforementioned because of the "sudden on-set" of the issue and no indications of such issues historically.

Which brings us back to Para. 1 above???

Ken