sweating slab syndrome

Sweating slab syndrome (SSS) is a phenomenon in which an interior concrete slab (or other surface) develops condensation or "sweat" on the surface.  SSS is caused by a rapid change in temperature and humidity between the ambient air and the slab, which surpasses the dew point.  The dew point is the temperature at which moisture in the air will condense upon contact with a colder surface.

For example, if the concrete slab is at 65 degrees F and exterior doors are opened to allow a rapid increase in air temperature with high humidity, moisture will quickly develop on the slab.  From the weather conditions in Clearwater, Florida, the dew point was 77 degrees F, which means that the concrete will begin to sweat if colder than 77 degrees.

Sweating Slab Syndrome at Dew Point of 77 Degrees

Sweating Slab Syndrome at Dew Point of 77 Degrees

The result is the quick development of sweat on the slab.  The part of the concrete which was covered by a box did not sweat.
Sweating Slab Syndrome Prevented by a Box Covering the Concrete

Sweating Slab Syndrome Prevented by a Box Covering the Concrete

Virtually all of us have witnessed this same phenomenon in a vehicle when interior conditions are substantially different than outside conditions and condensation develops on the windows.

Flooring should not be installed with conditions of sweating slab syndrome.  The conditions must normalize.  Avoid the problem by maintaining regulated HVAC conditions.

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