I have approx 18m2 of rosewood parquet flooring in my lounge, which has been down over 50 years and is set in what I presume to be bitumen. We had the flooring skimmed and revarnished about 8 years ago, but now want to take it up and relay carpet as the blocks have come loose and rattle (even under carpet, which was laid over the parquet when we bought the house).
I'm not sure of the best way forward. I know I want to remove the blocks (and possibly sell them if they have any value), but I'm not sure what to do with the remaining floor. It will need making up to the height of the surrounding floors (the blocks are about 15mm deep), but once I've removed the blocks I'll be left with a black, tarry mess. I've thought about laying some 15mm ply or chipboard, or concrete/screed, but having googled both I'm not sure which would be best. Is 15mm deep enough for concrete; would it crack and break up? I don't know how flat the floor is underneath the blocks so I don't know whether ply would lie flat itself.
Can anyone offer any suggestions please?