White powdery build-up in garage?

[tordley]

My in-law has an unusual problem in her garage. She lives in a two-story condo. Whenever an object is left in the garage for a couple of weeks (such as a box of something or a bag of old clothing, etc.), it appears to have a white powdery residue underneath it when it gets picked up. The powder looks like it could be hardwater deposit except it's very soft, like baking flour. It also seems to develop directly under the objects and not in the main walking path or driving area of the floor. Can some sort of vapor be seeping up through the concrete floor and condensing on the underside of these objects?

Thanks in advance,

Tordley

[pushkins]

You got it in one !

What your experiencing is the "sweating" from the concrete to the object placed on top of it. The powder you refer to is a type of mold.
Mold needs two things to exist 1. moisture and 2. a dark place, under a box is both.

[alyssa]

Mold can be a potentially bigger problem that can end up taking over the inside of the wall so be careful! My parents are dealing with it now and its been one thing after the other. When we moved the sellers brought in a mold sniffing dog to check out the house. Luckily we didn't have any.