Brown spots/blistering on interior wall

[Chuci]

Last year I suspected I had a leaky gutter as one of the rooms had damp coming through the walls. Had the wall redone, filled and painted as well as the gutter fixed. I'm still getting these weird yellow stains coming through.

The other day I had just that wall repainted as every other wall is fine. Guy used zinsser bin primer and then my usual dulux matt paint on top. All looked decent. Wake up next morning and I see a bit of yellow again. It's not rained so I don't know what it is


This is an extreme close up and it's not very obvious but this is how it always starts.

This is what it looked like before I had it painted:



Today I bought some of the zinsser oil based cover stain spray and sprayed the tiny brown patches, let it dry for 2hrs and then painted over with the same dulux paint. All looked OK but just now I can see a little bit more brown patches in a different area.

Any idea what it is? Should I just get the paint version of cover stain and a roller and go over a large part of the wall again? Or is it something completely different.

Worst is, I'm looking to sell the place so really don't want to have to smash the wall and incur a huge cost.

Thanks in advance. I'm a complete rookie to decorating so appreciate the most idiot friendly answers

 

[sparkwright]

If you're selling the place, just go over with the zinsser and emulsion every now and then.

If you have a conscience, get the damp problem looked at (if there still is one)

It is possible you have rubble in the cavity that needs removing.

Or there could 100 other reasons.

 

[Wayners]

Lime plaster and wrong emulsion trapping moisture? Is there a cavity or solid wall?

 

[Chuci]

Lime plaster and wrong emulsion trapping moisture? Is there a cavity or solid wall?

Just a solid wall

 

[Wayners]

Solid wall no cavity then. That's why they rust. Grinder. Fill. Breathable paint