help with damp looking plaster

[Steven963]

hi
i really hope somebody can help me.
ive been having problems with this plaster since I moved in this house it appears to have damp marks on it but they come and go.
I really don't know what to do anymore.
they are at either side of my chimney breast, I have a vent in the chimney in my bedroom which has a vent cover on. I have taken this off and looked through it and there seems to be lots of loose bricks inside piled up would this cause the problem?
I will upload the pics






the patches wont go higher than 5 inches high.
thanks

 

[Doggit]

Is this on the ground floor. Chimneys don't tend to have a dpc, but with all that rubble there, it could be pulling moisture up from the ground, but do the marks appear after it's been raining, as the soot in the chimney can leach moisture across the brickwork to the plaster.

 

[^woody^]

Is this bedroom and damp on the ground floor?

 

[Steven963]

Hi
Yes the pics of the chimney are in the bedroom, and the damp is on the ground floor.
the chimney downstairs has been blocked off so there is no fireplace.
the marks come and go I am finding it very strange.
As you can see the marks don't come up very far would I have to remove the laminate floor to see what's underneath?

 

[Doggit]

You'll need to hack the plaster off, Inject a chemical dpc (for good measure) apply a cement render (using washed sand) with a waterproof render in it, and then replaster. Or you could look on the safeguard website for a quicker, albeit more expensive, solution.

 

[Steven963]

Would I only have to have the affected walls rendered? Also how much would that roughly cost?
Would I get a builder or a specialist damp company

 

[Doggit]

You'd only do the affected walls, and if a specialist company does it, then you get a warranty (that may well be useless mind you) but a builder should be just as good, and possibly a bit cheaper - as usual, get several quotes. Sorry, we can never give costs on here as we're not on site.