I wonder if anyone can definitively answer the following 2 questions; The floor of my 1963 bungalow was originally laid with either parquet or marley tiles. Under this is that lovely thick sticky bitumen over concrete. As dpm under concrete didn't become normal until 1966 is it likely this bitumen was also the dpm? When laying real wood parquet over concrete subfloor is it considered normal practice to also lay a visible dpm? Any answers to these questions would be hugely appreciated as I am just about to go into battle after a complete botch job (following a flood) - new floor blown!