Question:
After tanking my garage floor using 'thoroseal' about 6 weeks ago, I have
now put some vinyl flooring down. Although the floor appeared fine with no
floor covering on it, since I put the vinyl down there appears to be damp
patches underneath the vinyl. Is this just condensation? If so, how do I
stop it so it doesn't damage the vinyl flooring?
The thoroseal should create a watertight seal, and given the good weather I
doubt very much that water is coming through the floor. why is moisture
becoming 'trapped' between the coating of thoroseal and the vinyl?
Answer:
Condensation seems unlikely at this time of year unless you are using any
moisture-producing equipment such as a tumble dryer that is vented into the
garage. I have no idea how effective Thoroseal is but it is quite easy to
test it using some putty or plasticine and two small pieces of glass, such
as left-overs from small picture frames. Choose two areas of concrete, one
where there is the damp problem and one without, and dry the surface of the
concrete using a hairdryer. Then make two circles of plasticine or putty,
and press a piece of glass onto each surface. The air inside the glass needs
to be trapped and sealed from the outside air. If a few days later you have
any misting or water droplets on the inner surface of the glass then it must
be moisture coming through the concrete and Thoroseal which is condensing on
the glass. In which case a layer of builders damp proof membrane between the
concrete and vinyl should prevent moisture reaching the vinyl and if that
works it confirms it was moisture penetrating through the concrete. If you
don't fix this problem you will probably find that mould will grow under the
vinyl and the vinyl will become discoloured.
