Now that we have removed the wet carpet from our basement floor, we can
see a few cracks in the concrete.
Although the recent mini-flood was caused not by water coming up through
the cracks but by water overflowing into the house from a flooded window
well, ought we to fill the cracks before laying new carpet or carpet tiles?
Absolutely. And you should also do a test to see if there is some
moisture coming up through the slab. Put some plastic down on the
slab and tape down the edges. Let it set for a couple of days and
then remove the plastic. If the slab is darker where the plastic was,
you have moisture issues that need to be addressed.
Let the concrete dry thoroughly. It may take a few weeks. You may need
a fan and a dehumidifier.
Fill large cracks with mortar. Every slab has hairline cracks. Large
cracks, especially those where the two sides are different levels,
should be examined by a foundation expert.
Seal all cracks with something like RedGard.
Thanks for the reply.
The cracks are little more than hairlines. Most of the floor already has
some kind of coating on it, but I have no idea what it is. Will the
RedGard work on top of an existing coating?
I had a long crack in my garage floor. I just blew it clean with compressed
air and filled it in with sanded tile grout. In my case the maximum crack
width was about 3/4" with most of it under 1/2" the crack is over a decade
old so I am taking a chance it will not move more and open the crack again.
If I thought it would move, I would have used a flexible concrete caulk.
One year and still stable.
I would attempt to remove the coating before applying any new adhesive for
carpet, it sounds like residual adhesive. A floating floor may be OK if it
is smooth enough. A floor sander might work but if it is too gummy then a
solvent (like paint remover) and scraper might be in order first.
It is not necessary to have a dry surface for Mortar or Grout. For a tube
dispensed caulking product, read the label.
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