Looking for some advice on this. Recently had some asbestos tiles removed, and underneath is whatever was used to stick the tiles down - I've heard a lot of people say it's bitumen, I've attached some pictures in case that helps identify what it is. I'm aware that this may also contain asbestos, after a lot of faff when the tiles were removed, I'd rather find a way to just leave this as is and go over the top of it. Looking at other posts, it seems that this bitumen tile combination was often used in place of a proper dpm. I have no idea if that's the case here. Ardex na seems to be the recommended product for going over this kind of thing. I've not really got a lot of height to work with - can only maybe raise the floor level a total of 4mm. So the recommendation from ardex to level, liquid dpm, level seems to be out of the question. From what I've read, it seems like the best option is to put down a layer of ardex na, and then some sort of liquid dpm, then put the underlay on top of that. But I have no idea if that's a sensible plan at all. Would really appreciate any advice on this.
Ardex na will be fine. If your subfloor reads below 90 rh you can use timbermate and tape the the joins. most underlays with a built in dpm will protect the floor. You want to make sure you dont have any rising damp first or it will collect beneath the underlay. A moisture test will be your best bet
