Limestone onto concerete floor - TilersForums.com

[Gnasher1981]

Hi all, I'm raplacing my vinyl kitchen floor with natural limestone tiles.
Having pulled up the old floor, I have discovered the concrete underneath is damp.
It is drying out pretty quick, in one day it's mostly gone, but I'm wondering if this is an issue?
Do I need to have the floor DPM renewed, or paint a layer of liquid DPM on the concrete, before I lay the tiles?
Thanks in advance.

 

[Tile Fix Direct]

The vinyl tiles may have been acting as a barrier to rising damp. You have removed them and the surface has dried but the screed could still be wet and the damp still rising (but evaporating before it looks wet). Adhesives and limestone can be fixed to a damp screed, but you really need to get the screed tested with a meter and find out if you have a problem as the damp could discolour the limestone, cause smells and damage the fabric of the building. Test the floor and if damp find out where the water is coming from.

 

[Gnasher1981]

The vinyl tiles may have been acting as a barrier to rising damp. You have removed them and the surface has dried but the screed could still be wet and the damp still rising (but evaporating before it looks wet). Adhesives and limestone can be fixed to a damp screed, but you really need to get the screed tested with a meter and find out if you have a problem as the damp could discolour the limestone, cause smells and damage the fabric of the building. Test the floor and if damp find out where the water is coming from.

It may be worth noting the kitchen is an extension, built in the 80s. The house is a 30s build.
I have used a moisture sensor, it seems there is still damp, especially near a wall with no pipework. There does not appear to be any damp on the walls.
My guess is the DPM installed when the extension was built has failed.
Can I paint over the floor with a lquid DPM?

 

[Tile Fix Direct]

You could use a liquid dpm. However, sealing in the damp problem could then lead to damp moving up the wall. Previously the gaps in the vinyl tiles may have been sufficient to prevent this. Probably over complicating this but worth considering.

 

[CJ]

If you had sheet vinyl down, it could have sweated, leaving darker/dampish areas. Leave it for a few weeks.

 

[Gnasher1981]

Thanks for the responses.
If there is a damp problem, what is the best course of action?