There are two reasons why concrete sweats. The first and most common reason why concrete sweats is that the concrete is cold and the air is warm. When the concrete is cold and the air is warm, the moisture in the air hits the cold concrete and condensation forms on the surface. Have you ever taken an ice cold soda and left it on the counter? The entire outside of the soda can will be dripping wet with water because the soda is cold and the air is warm. The same exact thing happens with concrete. Sealers can’t stop condensation. Sealers can reduce the absorption of water on the surface, but they can’t stop condensation from forming. In order to stop concrete sweating caused by condensation, you need to either warm up the concrete or cool down the air temperature.
The second cause of concrete sweating is sub surface moisture. To be honest, this is very rare, especially in a garage or warehouse. Subsurface moisture is caused when hydrostatic pressure pushes water and moisture up through the concrete from below the surface. It is very common for concrete slabs to have issues with moisture, but concrete sweating is rarely caused by subsurface moisture pushing through. If you have large amounts of water pushing up through the surface of your concrete, or in through your walls, you may need to call a concrete company to determine the source of the water and how to stop it.
There are a few things you can do to try and reduce concrete sweating, and protect concrete against the damage and deterioration caused by the absorption of the condensation.
1. You can run a de-humidifier to try and reduce the moisture in the air. Unfortunately, because temperature difference is a factor, you may not notice much of a difference at all.
2. If you are worried about water stains, or deterioration from water absorption, you can apply a water repellent sealer or a concrete coating. Typically, condensation on concrete doesn’t produce enough water to cause any issues, but if it gives you peace of mind, it never hurts to seal concrete.