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DIY Forum >> Building Questions >> Dark patches on internal wall
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Message started by ellenjr on Apr 27th, 2016, 2:04pm

Title: Dark patches on internal wall
Post by ellenjr on Apr 27th, 2016, 2:04pm

We're a couple, not got a clue about DIY so be gentle with us!
So we've been in our semi-detached house for about 10 years and for most of those years we've lived with dark patches on our living room wall.
The wall is plasterboard and patches are at the joists in the wall - not at the hollow bits - if that makes sense?
Its an internal wall so our wall backs onto neighbours living room wall. The wall has dark regular, almost circular even spaced patches which look like damp.  We've had the wall painted and wallpapered but they keep coming back. Recently got in 2 builders and a damp specialist who all said they had never seen this before! There is no damp in the wall. One builder said it was "dot and dab" and thought that was the problem.
He thought may have to take all the plasterboard off and re-do and then re-plaster.  I'm hoping not!
Really grateful for advice as don't know where to go to next.

Title: Re: Dark patches on internal wall
Post by thescruff on Apr 27th, 2016, 5:31pm

Do they grow or shrink ?

Perhaps a couple of pics would be clearer.

By the sound of it I would probably try a stain block and paint and see what happens.

Is there a fire place/chimney breast close to the problem.

Title: Re: Dark patches on internal wall
Post by woodsmith on Apr 27th, 2016, 8:20pm

Has anyone tested this with a damp meter? It sounds to me like damp tracking across the dabs (blobs of adhesive used to fix the plasterboard to the brick or block wall).

If the patches are more prevalent at the bottom then you may have a problem with damp coming up from the floor, if they are spaced all over the wall and go up to the the ceiling then as Scruff suggests it may be from a chimney, possibly next doors or perhaps the chimney brest in your house has been removed?

if it definitely isn't damp it may be some sort of chemical reaction between the dab and the wall, in which case stain block would normally stop it.

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