How to Check a Concrete Wall for Dampness

Checking your concrete walls periodically for dampness is a good idea, not only because you want to detect any structural problems, but also because any mold that starts to form can be a health issue. Usually mold isn't hard to spot, as it discolors the cement. But if you want to be absolutely positive that your walls are dry, use a plastic-sheet method recommended by the American Society for Testing and Materials.

Clear polyethylene plastic
Wide concrete-fiberglass mesh tape or clear packing tape

Instructions

- 1
  Place an 18-by-18-inch square of clear polyethylene plastic on the concrete wall, and seal all four edges with wide concrete-fiberglass mesh tape. If concrete-fiberglass mesh tape is not available, use clear packing tape. You will only need four 20-inch strips of tape to secure all four sides of the plastic to the concrete. Clear plastic can typically be purchased in rolls at building-supply and home-improvement stores.
- 2
  Avoid exposing the plastic sheet to excessive heat or direct sunlight. This may give you a faulty result, as extreme heat and sunlight can cause sweating under the plastic. The moisture you see in this case isn't coming from the concrete.
- 3
  Allow the plastic to remain in place for 16 to 24 hours. Signs of condensation on the underside of the plastic or darkened concrete under the plastic indicate excessive moisture. Take steps to eliminate the moisture.
- 4
  Combat dampness by covering the concrete walls with a wall-grade epoxy resin. Mix the epoxy resin according to the manufacturer's directions. Apply the epoxy resin with a quality paint roller, thoroughly covering the surface. Allow the coating to dry for six to 10 hours before applying a second layer, which should also dry six to 10 hours.

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