Marks on plaster after dampproofing

[tiddlywinks]

Hello. Four weeks ago, we had some damp remediation work in our Victorian terrace, involving injected damp course, damp proof membrane, bonding coat and plaster. A few days after it was finished this pattern appeared on the surface (no white salty fluff but a crystal-like pattern).

The damp company and decorator were surprised and said they hadn't seen anything like this before. Then I called British Gypsum which said it should be taken down and redone as they thought it must be coming through from the brickwork, but I don't see how as the membrane is floor to ceiling in kitchen where marks are worst. I'm now stressed out as I have decorators and new flooring booked in the coming 3 weeks and I don't know what to do.

I did think at the time, the bonding coat seemed very wet (water was running down the wall). I believe there is a bonding coat behind the membrane as well as in front.

Any thoughts/advice appreciated. Thank you.

 

[Wayners]

That can happen. Plaster don't always dry the same colour.
Just how it is.
If you think it's damp tape some plastic over and water will show under after a few days.
I don't think that's damp

 

[ree]

OP,
Is the wall solid or cavity - do you have CWI?
What kind of membrane was used?
Who first said that you had a damp issue that required whole wall remedial treatment?
What you say the "damp company" have done as remedial work to deal with damp in that wall is more or less wrong e.g. you dont use any gypsum plaster - if necessary you use sand & lime render.

 

[tiddlywinks]

OP,
Is the wall solid or cavity - do you have CWI?
What kind of membrane was used?
Who first said that you had a damp issue that required whole wall remedial treatment?
What you say the "damp company" have done as remedial work to deal with damp in that wall is more or less wrong e.g. you dont use any gypsum plaster - if necessary you use sand & lime render.

Thanks for your response. It's a solid brick wall. They used a fleeced grey waterproof membrane (don't know the name) with BH Thistle bonding layer and normal gypsum plaster on top I believe. I think they did the whole kitchen wall because there was a damp patch higher than 3ft from the ground. In other rooms it only went half way up. The surface pattern is s bit concerning as it looks like marks made by crystals (presumably salts). Most of the wall looks like it's drying ok though there are still a few darker areas where plaster is still damp.

 

[ree]

The Thistle bonding is a gypsum plaster - over time it could possibly disintegrate?
The membrane sounds like one of the newer ones introduced over the last say 10years - from what I've heard they are OK - but damp proofing is for the long run so we'll see.
As for bonding coats before and after the membrane - from what I understand these new membranes can be skimmed with a specialist skim finish, no bonding needed except on the wall as a first coat.
However, no render or plaster should be streaming moisture.
But I have no personal experience so maybe you will have to wait & see when it dries.