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. I've just put the property back on the market so I just want it looking decent for now. Guy used zinsser bin primer and then my usual 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 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 my regular 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

[Square Feet]

That looks like an old property with solid stone walls.  If that is correct then it can take up to a year for a wall to fully dry out after it has been soaked right through.  I had to get a wall tanked for this reason - that then allowed the wall to dry outwards rather than inwards as yours is trying to do. 

Damp proof paint like zinsser will basically seal that part of the wall to some extent, but it may keep coming back though a wee bit until it's completely dry.  For a bodge to get it sold I would just slap more damp proof paint on and then paper over it with thick lining paper. 

There is another possibility that it isn't damp but some other sort of staining ie tobacco, but I assume you have discounted that already. 

[jayc89]

Having an older property myself, I'm not a great believer in water proofing/tanking etc. IMO if there's a moisture problem using these types of products just move it elsewhere. The source of the problem needs addressing, not the symptoms.

I'd be looking at things like what's on the external face - cement render, cement pointing etc? It needs to be lime and preferably a hot lime mix to NHL. Anything cementious will trap and push moisture internally, which could well be the case since you mentioned you had a leaking gutter. 

[Chuci]

Thanks both! You're both correct in that it's an old property. I can't be certain about the tobacco theory as I'm not sure what the previous owners did in that room. 

[Square Feet]

If you are just bodging it to sell then liberal applications of stain blocker and then put some furniture in front of it 😂

[Chuci]

2 hours ago, Square Feet said:

If you are just bodging it to sell then liberal applications of stain blocker and then put some furniture in front of it 😂

Do you happen to know the difference between the zinsser sprays vs the actual paint version. I've only got the spray at the mo but wondering if I should just buy a can of the proper stuff 

 

Using this one at the mo

 

Edited November 25, 2023 by Chuci

[Square Feet]

When I have used sprays before it has just meant a very thin coat. It's much better to use a brushed on one - you will get a thicker coat that way.