Bitumen/DPMs and parquet flooring

26 Jan 2011
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United Kingdom
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!
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The black sticky stuff is the original tile adhesive. It is bitumen but does not constitute a DPM. I does have some moisture suppressant qualities but nowhere near enough to prevent moisture ingress into modern day flooring and water based adhesives. It will need removing which is a tough job! If left down and simply covered, the bitumen may bleed into whatever is put over it. Scrape as much as you can off the floor and then try a copper plate sanding disc. Once you have removed about 75% of it, prime the floor with neat P131 primer and when dry, cover with Stopgap green bag mixed with 114 liquid. Both these products are available from F. Ball stockists.
As Glueman mentioned, the original bitumen glue would likely have been thought of as partly a DPM, when i am doing parquet block repairs to concrete floors which have a bitumen residue left on it, i apply 2 coats of a liquid dpm, either Lecol PU280 or Sika Rapid, both are superb products and 2 coats is normally enough to form a full dpm, although you can put a 3rd coat down and broadcast in some kiln dried sand to get a really good key for the adhesive.....we then re-fix the parquet blocks back in position.

I've repaired hundreds of m2 using this method and as yet never had a block come back up, i'd recommend using adhesive from whichever dpm manufacturer you decide to use, commonality of products always helps.
This method spares you alot of grief trying to remove sticky bitumen from the concrete subfloor which is a nightmare.

The top manufacturers always have good technical dept's who will be happy to answer any queries.....hope this helps.

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