Hello, I’ve recently purchased Mapei Ultraplan self levelling compound to level an extension concrete floor before I install click vinyl flooring. I have found the floor is holding some dampness and wish to cover with a liquid DPM before levelling. I’m new to this game and am trying to find out a recommended, not too expensive liquid dpm to use and also can I simply apply the levelling compound directly over the dpm or do I need to use some sort of primer before the compound? Any advice would be gratefully received!!!