Help please - is this damp or something else??

[alexisj]

Dear all,

We had an attic conversion two years ago and about 9months ago, the paint on the external wall on the side of the staircase started to peel off.

Called in the builder who did this and he said it's because they forgot to put base layer of paint in.

However the peel keeps expanding and now I can see all the salt like white powder substance appearing on the wall and the plaster also cracked.

I haven't seen mould on the wall until I took down the paintings on the wall and the back of the paintings are covered in green mould.

Now I also see some small bubbling on the more distant side of this wall.

I attach pictures for above.

Have anyone got experience with this before that can advise us what this really is? Would appreciate any sharing and comment. Tbh I lost faith in our builder and don't want to trust him any more.

Many thanks!
Alex

And air the space

This is all getting very scary 😨😱

But earlier OP said it was an external wall!

The wall with the problems is an outside facing wall. The bathroom wall is an adjacent wall that connects to this wall in question. I hope that's clear...

Scraping off more paint will probably make the pattern, and perhaps the source, easier to see.