Q.: At a building we built 4 years ago, water appears on the sidewalk near one entrance every morning during the cooler fall months. It usually freezes and is a slipping hazard. The condition is localized and as soon as the temperatures get colder into the winter, the problem disappears. Another entrance 250 feet away has no condensation or icing problem.

Before I learned about the problem, the building manager put a sealer on the concrete because he thought water was coming up through it. I covered an area with a plastic sheet, though, and found that moisture was condensing on the surface. The sealer keeps it from soaking into the concrete so the problem is worse than ever.

Is there any way to prevent this condensation? The owner is concerned about possible slip-and-fall injuries to people using the building but doesn't want to use deicing salts on the concrete.

A.: Either of two relatively low-cost approaches might work. Diamond grooving would provide channels for the water and perhaps allow it to run off instead of freezing on the surface. Or mechanically scarifying the surface might also give enough texture to skidproof it even if some ice forms in the valleys. If you try scarifying, it also might help to stain the concrete a darker color so it absorbs more heat from sunlight.