Construction Resources and Support

[Guest]

A couple of years ago a fellow DIYer painted her basement walls with Dry-Lock waterproofer and the floors with Dry-Lock floor paint. She has a workshop area, gym area, and storage in her basement. She thought her basement was dry, as she never had any water, and ran a dehumidifier. However, in the workshop area she has large rubber mats, and has noticed that a light coating of water collects under the mats. How can she prevent this water? Her house does not have a high water table. Even if it did wouldn't she be getting water from the area on the floor where the slab meets the walls. FYI: There are no cracks on the floor. Is this something she can prevent? The simple solution would be to get rid of the mats, but she likes the non-slip surface.



Advice:

In many cases this is simply condensation. The best way to control condensation is make sure that all windows and doors in the basement are closed and other potential air leaks are sealed. Next keep running that dehumidifier. If possible have it drain automatically so you don't have to empty it -- some will shut off when full. This will also allow it to run at maximum efficiency. The other possibility is that you have a case of vapor transmission: when water vapor comes up through the slab and is then trapped under a non breathable material, condensates and causes a puddle or damp spot. One way of testing this out is to tape a piece of plastic to the floor about 18" square and leave it for a few days. If there is moisture under it when pulled up it is vapor transmission. To test for condensation there are do-it-yourself test kits available you can set on the floor.

[Guest]