Garage floor

[Cookie]

What causes dark stains on the garage floor? Thanks.

[hj]

Ground water could only come up through the concrete if it was under pressure and that is very, very unlikely. Put newspapers on the floor under the car. It is probably fluid leaks of some kind. Wherever the stains mark the paper, the leak is somewhere above it.

[Mikey]

I had a similar stain in part of my garage which is now a formal laundry room. I just covered it up yesterday with ceramic tile. There's a similar stain in the master bath, which will be tiled next week, Imshallah .

[prashster]

It doesn't sound like water seepage. Water doesn't behave like that - in isolated spots.

You need to take a picture of this and post it.

Could the stains be mold? Dampness and darkness would make it appear on the surface. Light and drying out would make it recede below surface. I doubt, though, that you'd mistake mold for a liquid stain...

Another way to refute the theory that it's water seepage is to lay some clear polyethylene down in a large square. Tape the edges sealed. If you get no condensation after a few days, then you don't have moisture seeping through the slab.