Looking for advice on applying barrier to solid floor

[user256]

I've also got contractors in dealing with damp caused by a leak in the new part of my property, and with water ingress issues related to the roof. They're recommending I put down a damp proof layer on this floor here in the old part of the building. This makes sense as it has previously damaged carpets (can be seen in pictures) but little concerned by some things I've seen here and elsewhere.

This is the solid floor in my house, I have it on good authority that the cracks are historic rather than new but the ground level outside is too high (a problem I plan to tackle shortly) so odds are moisture is getting in from this. What should i be doing, will putting down a damp proof course cause problems or solve them?

 

[Toby Newell]

I would screed and apply a liquid dpm, this is more permeable than a sheet, I always use one when fitting a wooden floor. A slab dpm in your case and in most cases isn't going to solve an existing damp issue, rather it is simply going to reduce the rate at which moisture expires through the top floor. The issue is your raised ground level and possibly adequate drainage, then heating and ventilation. Moisture may still rise via the walls from splashback above the dpc from the raised ground level and especially if the dpc is damaged (often is in very isolated areas, eg corners of houses that have subsided) A slab top dpm is primarily there to protect the floor coverings, not to stop 'damp' your slab should have a dpm underneath. The slab could be wicking moisture from the walls.

 

[user256]

Many thanks Toby - is a liquid dpm really going to be permeable though? will this not just lead to all the water building up in the corners?