Damp patches on dabs?

[Jonathan---]

Hello - long story but i will try and cover it all.
When we bought our house, the upstairs bedroom had damp at the top of the wall and edge of ceiling. This is the adjoining wall of the semi and has a chimney breast on. On going into the attic above there was moisture all over that wall too- working it's way down to bedroom below.
We had the chimney re dashed which didn't help but on having the roof overhalled (not re roofed) they noticed a hole in one of the valleys. This was replaced and the wall seemed to dry out.
In the bedroom we knocked off the damp plaster, dabbed new boards on, and skimmed.
12 months later we keep getting round damp spots showing through the paint, usually i can paint them with sealer and cover them but more keep showing up. The attic wall seems still dry.
I am sure it is just moisture in the chimney being soaked through the dabs - is there anything i can do to stop it? Other than re boarding with foil backed boards? (The chinmey pots all have cowels.)
Thanks.

[The Builder]

I know hindsight is a wonderful thing Jonathan, but it's never a good idea to dot & dab onto a wall that has had damp problems. In time, the wall should dry out completely if the problem was fixed, but it does take time.
Screwing treated battens to the wall would have been better. You can still do it now over the existing plasterboard. Fix "Celotex" insulation boards between the battens, then plasterboard and skim.
Alternatively make up a timber stud partition and stand that inside the wall. You could make the partition as thick as you like with a good thickness of insulation.
For a remedial job................ maybe .................. Google "Zinsser Bullseye Primer" ............ an American range of super pukka stain blockers..............
Good luck

[Jonathan---]

Thanks! Nobody ever mentioned that (builders ect) but it does seem a good idea. Think i will try the stain blocker first as to be fair the stain's i have covered haven't really returned. The stains have got worse in the wetter weather however which makes me think there could be moisure getting in via nextdoor or from the roof or chimney. Also would rather not lose any size on a small room and the wall is stepped back after the chimney breast so i'd prefer to take off and try again with treated battens worst case scenario.