Our British wood flooring Association colleague Matt Bourne brings you the following advice when faced with bitumen on your underfloor or subfloor:
Question: "Is there any way we can screed over bitumen when we want to glue a wooden floor down?"
I prime with a neoprime primer use acrylic leveling compound over the top ONLY if the Bitumen is well stuck down and very thin. This will give you a good flat base. You can then use a epoxy dpm paint to deal with any moister problems.
Now please remember that this is NOT a recommended method by the product manufacturers. You are relying on how well the bitumen paint is stuck to the subfloor!
Do not use a latex flooring smoothing compound! These compounds are good for nothing and normally used by people who have no idea. ( 95% of builders ) They will stick to anything you put them over but have very little strength, so basically you can NOT use a epoxy compound or any sort of glue over the top!