Q.: I live in Louisiana. Many times my garage and shop floors become very wet and slippery during the winter, when the air temperature changes quickly from cold to warm. What can be done to concrete floors to prevent this from happening? I'm also installing a new shop floor and would like to know what can be done during construction to prevent this problem.

A.: Water is probably condensing on the floor surface due to temperature differences between the air and the concrete. Warm air holds more moisture than cold air. When the air temperature increases rapidly, the concrete temporarily remains colder than the air, causing moisture in the air to condense on the floor. To verify this, use duct tape to seal the entire perimeter of a 2x2-foot square of plastic film to the dry floor. When the floor gets wet again, check to see if it's wet under the plastic. If it isn't, condensation is the problem.

If your shop or garage area is enclosed, a dehumidifier would help keep the floors dry. You might also consider grooving or grinding the floor to reduce the slipping hazard. You can rent grinders, groovers or scabblers from equipment rental houses. The disadvantage of rough-textured surfaces is that they are hard to keep clean.

For new construction, consider placing the floor on 2-inch-thick insulation board. Installing in-slab radiant heating will decrease the temperature difference between the floor and air, and possibly prevent condensation, but this is a more expensive alternative.