Expert: Stephen Hayes - 4/10/2011

Question
Hello,
Our house was built in 2003 in Southern California.  We started experiencing moisture in our lower cabinets, as did some of our neighbors.  After years of battling the builder, we have received an insurance claim with the builder's insurance carrier.  We have moisture extrusion from the slab.  We had calcium chloride tests throughout the house with the highest number being a "9".  It was explained to us that where the moisture was able to evaporate, there was no problem.  But where the cabinets were set directly on the slab, the moisture was being trapped under the cabinets, not being able to evaporate.  That moisture is coming up through the cabinet base and creating water damage in our base cabinets.  The recommended solution was to put in French drains around the perimeter of the house and tear out all cabinets, flooring, tub, shower pan etc. and seal the slab with a concrete sealer/moisture barrier.  The sealer that is being recommended is RedGard.  I have talked with other contractors and they don't think the sealer will work.  They say that sealer keeps moisture from entering the slab but won't keep moisture from coming up through the slab or only temporarily before it fails.  We plan on putting travertine flooring in so the sealer would not be able to be re-applied.  Your opinion would be greatly appreciated.  Thanks in advance for your time and expertise.
Thanks again,
Joel

Answer
Hi Joel;Thanks for your question.  Moisture in concrete is the overwhelming greatest cause of floor covering installation failures.  I am not an expert in home construction.  I could take some guesses, such as the building putting no moisture resistant ground cover before pouring the concrete.  The concrete not being properly mixed before pouring.  No proper screeding being done during the concrete pour.  The recent rains substancially raising the water table.  The foundation ground outside your home not being pitched away from the home.  The list goes on and on.  You need to find the exact cause of the moisture and solve it before any type of floor covering is installed.  The calcium chloride test is no longer the proper test to make for finding out the moisture in concrete.  That test only tells you what it was during the period of the test.  Not what it is today, tomorrow, before the test, etc.

The new test, which now supercedes all previous moisture testing is ASTM-F2170.  That test can be purchased, for a fee, from the website, <astm.org>.  ASTM is a company headquartered in Philadelphia, PA and Washington, DC that writes test methods, after extensive research, for, just about, everything that you and I use.  That test indicates, in part, that 3/4 inch in diameter drill holes are made in a grid system, down about 30% or more of the thickness of the concrete.  Then RH capsules are inserted in each of the holes and left undisturbed for 72 hours.  Then the tops of those capsules are read with a special meter, and the result is the moisture content in the concrete.  You need to contact a company that does that testing.  I believe a company called Wagner Instruments in Portland, OR supplies the capsules and meters.  They may be able to provide you with the name of a company in your area that does such testing.  After the tests are done, the capsules are forever entombed in the concrete and the drill holes are patched and leveled AFTER the moisture problem has been totally solved and eliminated, and then those patched holes are leveled before any type of floor covering is installed.

The amount of moisture in the concrete is then, acurately known.  To solve the moisture problem, perhaps digging around the perimeter of your home is needed, or a major dig to remove all of the concrete made to inspect the ground cover.  Because of the recent changes in the amount of moisture your area of the Country has received, may have reactivated any underground dormant streams that may have been present.  That's just another guess.  You really need a total investigation to find out the sources of the moisture and then totally eliminate it before ANY floor covering is installed.

If you have any other questions, please feel free to get back to me.

Cordially,

John Michaels