You are here:

Flooring and Carpeting/flooring; moisture/efflorescense


We live in Houston, Texas.  Our home was built in 1975.  Slab on grade.  Carpeting is installed throughout the house except for the kitchen and baths (ceramic tile) and entry way (which is terrazzo).  We have had a continual problem with moisture forming on the bottom of any flat object laid on the carpet.  After pulling the carpet up in several places, massive efflorescence can be seen, sometimes creating mounds up to 1/4" high.  If this powder is cleaned up, in a couple of days we observe crystalline "angel hair" structures that can be an inch high.  The ceramic tile has been down for about 15 years.  It only shows a little white powder through the grout in two or three places.  The majority of the tiles are stuck down good.  None of them have popped up, but several of them make a hollow sound when tapped.  Don't know if that is just the installation or whether the moisture coming up has loosened them.  We have corrected a drainage problem by re-grading the yard.  We would like to install porcelain tile throughout the house now.  Do you think we have a reasonable chance of success?  Any advise you can give would be greatly appreciated.


Thank you for your question Inez,

    Well it sounds like you have the "mother of all" moisture intrusions. Houston being a significantly humid zone as well there on the Gulf. I simply have never encountered such a large mineral transfer as you are describing to me and your slab. Addressing the grade of the home is an important first step and an additional second step would be to now control the rain that frequently falls in your area as well. Directing as much of the cascading water from the roof by way of rain gutters is also a necessary process with long downspout that deposit the water at least 6 feet from the foundation. But...just because you have perhaps dealt with the primary suspect in your moisture equation doesn't mean at all that the problem stops right away. Soil that is covered by a cement slab could easily take months to begin to dry out as the area has been suffering from the problem for likely years so it will take time for the process to begin to fade and lose power even if what supplied the process has been taken care of. Do you know that there are "de-humidifiers" that can be employed in spaces where excessive humidity is present? Not only does the ground need to dry out but your slab itself is going to have to evaporate out first before the ground can begin to follow. This could take a long time to accomplish so I would allow some time for the moisture to diminish. Now that we are heading into the season where moisture is most prevalent and is added to by having the AC on even if condensation of the AC unit is directed outside (you may want to be sure that this pipe is also not continuing to contribute to your moisture issue and virtually none of the systems handle the water that is generated by the AC very well. This can be a significant amount of water that is not directed very far if at all from the house. Now the hollow tile could have been affected by excessive moisture but I would say not likely, tile is installed in pools all the time and is rarely affected by the presence of water as a general rule. So I would lean more to a settlement issue or just the expansion/contraction process that is constantly going on all year long. Sometimes the bond of the old adhesive just gives way and lets go for any number of reasons that may simply be unknown. So...installing Porcelain tile. I would give your conditions some more time to evolve and return to a more balanced condition. I would guess that the carpet that is currently in place is probably due for a change out as well based on what you have described to me. Of course a cement slab can be encapsulated by employing a paint/sealer or if a tile is desired as in your case there is a product called "Red Guard" that can fill the cement cells and create a surface whereupon a tile can be installed, once you have the current moisture issues under control. Ok Inez I hope this helps you with your unusual problem, feel free to return anytime...

Perry V.

Flooring and Carpeting

All Answers

Answers by Expert:

Ask Experts


Perry Vellenga


Ceramic Tile/Marble. I can answer questions about floor preparation, tile selection, layout questions, performance of products, expectations of finish, compatabilities, questions about grout and epoxies, evaluating an installer, asking the right questions to check competence...more? 33 years this August 2012/ many years in commercial application from exterior finishes to Mall store fronts/ interior finishes like floor packages in stores inside Malls examples: The Limited, Lerner/NY, Lane Bryants, Bombay Co., Now involved in Residential new construction covering all types of interior finishes and designs.


I worked in an exclusive field of floorcovering called "Tenant Development" which is by invitational bid only, by way of a National bid list. These are large floor packages usually over 3500 sq. ft. of 18" x 18" Marble and Granite and many other types of Marble and sizes. They are specialty stores where the floor package can cost upwards of $50,000 for one store. I have also done "Structure" stores and J. Riggins stores, Lane Bryant,Express and Body Shop stores where wood flooring is used. Presently work for a National Flooring Company in the Residential new construction arena that covers most interior design elements..Granite Slab tops/wood flooring both job finished and prefinished ect..

My response's are published all across the Internet and picked up by multiple Interior Design sites and Industry related web sites where people have questions...

too many most of which don't count...

©2017 All rights reserved.