I have taken up old five finger parquet in order to lay wood blocks. Underneath the old parquet is a thin layer of a black substance on the concrete presumably bitumen which was brushed on. Some of the bitumen has come away, and it is a level surface, and a friend has advised that I should put on another layer of a waterproof substance for damp purposes. There is no sign of damp in the floor of the house which is 40 years old and another suggestion was that I should leave it and lay the wood blocks down with just an adhesive layer. I have heard that if there was damp it should be allowed to come out.
Can anybody give further guidance which will be most welcome.
it's recommended that stone and concrete floors have waterproof underlay.
I think you've find that the black substance is from when the parquet was originally layed.
Regards and best of luck
Old bitumen is a big problem, as the previous poster said you really should have a DPM.
The best option here is to remove the majority of the bitumen a heavy duty scrapper or orbital sander. Then DPM the floor with an Epoxy DPM like Sika MB or Bona R410
You may then need to level the floor, if not you can stick wood directly to the DPM with modern Silane adhesives like Laybond L19, Bona R850 or Utzin MK100.
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