I’ve noticed a white powder all over the floor of the garage, even under some work mats we put down. It seems to be leaching up through the garage floors. Is this a sign of a bigger problem?
The white powder you see is “Efflorescence”. The concrete contains water soluble salts that are the source of the white deposits. Also, the dirt under the concrete carries the same type of salts. If your concrete is new, there should be a vapor barrier under the slab, and the deposits will diminish over time and are nothing to worry about. However, if your concrete is over ten years old and you are having this problem, that may mean the your vapor barrier has failed, if indeed there is one at all. If the latter is the case, you may want to check the drainage around the perimeter of your garage. You can also clean your floor with a dry scrub brush, sweep thoroughly and apply a clear concrete sealer, but if the moisture is coming up from below, the sealer might not work.