I've removed a section of herringbone oak flooring over concrete,
installed in 1929. They used some black
stuff for a substrate that's now hard, glossy and brittle. I was
wondering what it is, and the best way to remove it.
Sounds like it is an asphalt based mastic.
The VOCs are long gone; however, what is left will probably burn if it
gets too hot.
I'd try a 1,500 watt heat gun and a putty knife.
Under no circumstances would I use an open flame torch of any kind.
Be prepared to get a mask if you start to smell vapors.
Is it entirely necessary to remove it? Do you need to get down to bare
If you are going to cement new flooring down, you might save yourself a lot
of trouble by seeing if the adhesive for the new flooring will adhere to
the black stuff.
If that's not an option, one of these bad boys will chisel it up in no
And if you're going to use one of those, then a pair of these will make your
day go a little easier.
The old mastics that were used for flooring used to have been made with
asbestos. If the year stated is correct, this may predate that. I would have
a small sample checked before I chisel, burn or anything else..
Over concrete is the key. Concrete sweats. Wood floor over sweating
area - bad news.
Normally resin paper and tar paper is used.
I suspect the layer of tar was higher quality tar paper and leveling.
In any case if it is removed, something else has to replace it before
adding wood over the concrete.
I recently removed some old vinyl tile flooring in our basement and
was also left with a thick black glue of some sort. The best way I
found to remove it was to use a steamer to soften it up then use
a razor blade to scrape it. It's probably a different type of glue
since yours was wood but the same method of removal might work. It's
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