salt neutraliser

[Sfrazi]

One of the walls in our garage has been boarded with insulation backed plasterboard and skimmed.

A dryer was then in use on this wall and as a result there is a damp patch behind the dryer.

We have removed the dryer from this wall and made sure its vented outside.

The problem is the damp patch has never dried out and has white fluffy deposits (salts I think).

What is the best way to get rid of the damp patch?

1. Apply a salt neutralizer?
2. Hack some of the skim off and re-skim?
3. Hack skim and plasterboard(revealing the insulation) and fill with appropriate filler?
4. Something else.

Any advise would be appreciated.

Thanks

 

[roughcaster]

How was the plasterboard fixed to the wall?

 

[Sfrazi]

It is an insulation backed plasterboard and was fixed to the wall by dot and dab method.

 

[roughcaster]

I would't start hacking off the plaster skim or cutting into the boards. I'm guessing your garage wall is a single skinned brick or block wall. Quite often, if plasterboard is dot and dabbed onto a single skinned wall, you will get damp spots/salts coming through, but your wall is boarded with insulated plasterboard. I know you've been using a dryer against this wall, and you suspect that is the cause of the damp patch. Try holding a hair dryer against the damp patch and see if it dries out permanently. If it does, brush the fluffy salt deposits off, and paint the area of wall with a neutralizer. I think it probably was caused by the dryer being close to the wall, keeping that area of wall constantly "damp", leaving you with the salt staining. 'Don't use water" to wash the area of wall, water/making the wall wet will take you back to square one.
The only other thing i can think of for causing a similar problem, would be if the insulation on the back of the plasterboard was damaged, and the dampness has drawn through a dab of adhesive, causing a damp spot on the front of the plasterboard. Have a tap around the damp looking area, with your knuckles, and see if it sounds hollow or solid. If it does sound solid, that'll tell you there's a dab of ashesive around that area, if it sounds hollow, i'd say the dryer caused the damp looking salty stain. Let us know how you get on.

 

[Sfrazi]

Thanks for the response.

The garage is block inside and red brick outside.

The area where it is damp sounds hollow but other parts of the wall sound solid so I guess that means there is no dot and dab around the damp patch.

It has been like this for many months and everytime I dry it the damp patch comes back.

What is the best way forward?