damp patch in the plaster

by jon

I had a interior wall (wall dividing my house to next door) skimmed over the existing plaster, and there is a patch of damp plaster approx 1.5 metres up the wall that never dried. ( 2 foot by 2 foot size). i wallpapered this wall some time after the skim was done and the paper got soaked through and discoloured.
Do I need to hack off the plaster and render and re-do ?


Hi Jon

That's a difficult one to answer - as there has to be a reason why this wall is damp. There are many possibilities:

The damp patch could simply be as a result of damp brickwork in this one area - which is going to take longer to dry out. This can happen during renovations for a number of reasons, and in order to facilitate the drying process, and not damage the decorations, wallpaper cannot be used - instead the plaster needs to be painted with a breathable non-vinyl paint. When the plaster has finally dried out then wallpaper can be used, but this process can take a year or two.

It could be rising damp. It can seem odd that the damp has appeared half way up the wall, but this can be due to a non-porous plaster being applied to the lower portion of the wall - in which case it is forced higher up the wall - coming to the surface where the plaster is more porous. If this damp patch is re-plastered with a strong render mix to hold back the damp - then the danger is that you can force it further up the wall.

If it is a case of rising damp then, one possible solution is to re-plaster the wall in a lime plaster that will let the wall breathe.

There may be another explanation as to why there is damp on an internal wall - but in order to work out the best course of action for plastering the cause of the damp needs to be established.

Investigate as much as you can and let me know what you think.


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