Bill, we have been having some problem with moisture in the foundation slab. We had to remove the wood flooring because of that. We had it tested for any leaks and am glad to say that they did not find any leakage because of plumbing. Now that we are ready to have tiles installed, some say that Redgard does a good job of preventing moisture. I have also heard that it takes care of moisture but not the Hydrostatic Pressure that is effervescent from the concrete slab and they recommend Ardex. I would very much appreciate it if I can get a right answer from you or anyone in the forum. Any helpful suggestion is highly appreciated.