Hi, I'm renovating a room in my house which has a concrete slab floor. I'm putting 50mm battens on it and 50mm Kingspan between - what I'm finding though is that water is collecting under the insulation at certain points - looks like damp is coming up from under - too much to be condensation, plus I noticed dark patches before I started, but wasn't sure if it was damp - now I know better. I think the sheeting under it may be pierced, or missing in parts. Can anyone suggest a method of dealing with this, short of digging it up and starting again? Ideally I'd like to be able to paint something on, or lay a membrane on top - I'm looking for something effective but preferably not too expensive. I need to deal with about 12m/sq if I do the whole floor.
Thanks,
R.