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DIY Forum >> DIY - Painting, Decorating & Tiling Questions >> Stains in paint and plaster
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Message started by Porkerspalace on Nov 4th, 2017, 11:23pm

Title: Stains in paint and plaster
Post by Porkerspalace on Nov 4th, 2017, 11:23pm

Could anyone advise on these stains? I have had them come through for years!

The plaster has been removed, new plasterboard and plaster has been put on but they reappeared.

The walls, stone and plaster are completely dry, no water or damp found.

The stains seem to grow in size!

[album]Porkerspalace&1509837614[/album]

Title: Re: Stains in paint and plaster
Post by thescruff on Nov 5th, 2017, 8:37am

What is the room used for. ?

What is the other side of the walls. ?

Have you tried a stain block. ?


Title: Re: Stains in paint and plaster
Post by woodsmith on Nov 5th, 2017, 9:00am

Is it a stain or is it damp? If you can get access to a multimeter, they are only cheap if you get a simple one from Maplins, put it on ohms and push the pins of the leads against the wall. If the wall is dry you will get no reading, if it's damp the needle will swing across.

It looks odd to me though, like something is getting onto the surface rather than coming out from behind. If it's not damp then stain block may well work.

Title: Re: Stains in paint and plaster
Post by Porkerspalace on Nov 5th, 2017, 11:20am

One is the hallway, the other is a bedroom.

The walls behind do not have these stains.

It's a stone cottage with insulation boards in a frame then plasterboard before plaster then paint.

I have tried a stain block and it still came through. Removed the stained parts of the wall and no dampness was found. The walls were then re done and the stains appeared again.

The stains are both halfway up each wall.


Title: Re: Stains in paint and plaster
Post by thescruff on Nov 5th, 2017, 6:54pm

Certainly looks damp with signs of mildew, also looks to be on the joint of the board. can you test it as per Woodsmiths post.

Could it be condensation behind the stud wall.

Did you fit a vapour barrier when you re-boarded

Title: Re: Stains in paint and plaster
Post by CWatters on Nov 6th, 2017, 8:06am

Is the insulation in the wall pushed to the other side of the wall leaving a small void on this side? Then perhaps cold air is getting into the void somewhere like the loft and causing condensation at joints ?  

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