Concrete Slab and Floor Water and Mold Problems from Water Wicking Up From the Ground Thru the Concrete
   Q. Is there a formula - or best practice - for the cure time on a concrete slab for a new home. Is there a way to measure the amount of moisture coming from the slab and or what is the threshold to be below so that mold will not grow? [Aug. 23, 2005]
       A. The concrete cure time is not the problem. Be sure the concrete has adequate amounts of waterproofing compound mixed into the concrete to turn the entire concrete slab into a impenetrable water and moisture barrier. Also, it would be wise to install the best possible rubber membrane waterproofing barrier beneath the concrete and to make sure the workers don't damage it during concrete installation.

       Q. First, I appreciate all the information on the website.  The question I have is about the basement floor.  I moved into a house a few years ago and laid vinyl tiles in the basement.  The squares started to pop up and leak in the seams.  Come to find out the moisture content is high in the floor.  It was taken up and carpet was laid, it was recommended that I tape plastic down as a moisture barrier; I am not so sure that was a good idea.  The carpet now is showing stains from the bottom and there are a few brown spots that make us concerned about mold.  Do I need to pull the carpet up, or have a company do it?  What can I do to fix the problem?  Can I lay any type of flooring in a high moisture floor that will not cause mold? [February 28, 2005]
        A. Unfortunately, your wet concrete floor problem is common. Many basement floors and many concrete floor slabs have no moisture barrier beneath the concrete, the moisture barrier was damaged during negligent installation, or it has degraded over time. The result is that water beneath the concrete wicks up from the ground into the concrete, making the concrete wet, which makes the tiles, carpeting, and walls resting on the concrete wet also and thus driving mold growth. You need to remove all of your flooring, clean the flooring to the bare concrete and then do it yourself or hire a cement contractor to install a new top layer onto the floor of at least one inch thick or more of cement containing adequate amounts of waterproofing compound to make the new concrete floor topping totally waterproofed and to be your new and strong moisture barrier. As to present mold growth in the basement, follow the 25 steps for safe and effective mold remediation You would be wise to mold test your entire home using do-it-yourself mold test kits [available from your local large hardware, home improvement, or safety store] or hiring a Certified Mold Inspector.

        Q. I believe there is mold underneath the sheet tile in my downstairs half bathroom.  There is not a tub there, just a sink and toilet.  The townhouse is built on a concrete slab in 1992. I bought it in 1997.  I noticed that there was a blue color around the toilet when I bought the place.  I figured I would just replace the flooring.  I didn’t know anything about mold.  Now I want to replace the floor not just in my bathroom but the whole kitchen.  If it is mold growing under my vinyl sheet tile floor, how would be able to get rid of it.  Would the glue used to put the floor down cause problems for me to remove the mold.  Over the past year, I have noticed blue areas have grown through out my floor in the bathroom.  A floor specialist said that the mold would be trapped under the floor and I could put new flooring over it.  I would think the mold could still spread throughout.  [Feb. 1, 2005]
        A. You are right that the mold needs to be removed. You cannot ignore mold growth, which can easily spread through out your entire floor area and into the walls, if it has not already done so. The mold growth beneath your floor covering is probably driven by water wicking up from the ground into the concrete. Your home has either no water barrier beneath the concrete, or a damaged or degraded barrier. If this is your home’s problem, you will also likely have water and mold problems inside walls resting on the concrete slab and beneath and in carpeting, etc. You need to have your home carefully mold inspected and tested by a Certified Mold Inspector. The problem can not be easily and affordably fixed. At least in your bathroom and kitchen area you can remove the flooring and glue, kill and remove the mold, and apply a surface layer of concrete containing waterproofing compound as a good foundation for your installation of replacement flooring. Learn the 25 steps for safe and effective mold remediation.

       Q. I'm in Prescott Arizona at 5500 feet elevation. On my concrete basement floor, I have a fuzzy white  mold  popping up in places. It has been a very wet winter and there was minimal moisture coming up through cracks in the concrete. What species of mold is most likely growing and how dangerous is it.  [Jan. 31, 2005]
       A. Any mold species in elevated levels indoors is unhealthy according to the U.S. Environmental Protection Agency. To learn the precise mold species of the mold growing in your basement, you need to send a sample to the mold analysis laboratory. Mold growing on concrete from a wet concrete slab is a very common problem. Your first step should be to fill and seal all floor and wall cracks with a waterproofing compound designed for such purposes---check your local hardware or home improvement store. If the problem persists, put a one inch new concrete flooring down over your present floor, with adequate amounts of waterproofing compound in the concrete mix to make your entire basement floor into an effective water barrier against water leaks and water wicking up from the ground into your basement floor. Learn the 25 steps for safe and effective mold remediation. You can also use one of the low-cost Mold Home Remedy Recipes available at Mold Mart.

      Q. We recently have had days of rain here in San Diego.  My cement garage floor (1st time ever) has white fuzzy mold all over it.  First I washed it with diluted bleach, the next day it came back.  I just poured straight bleach on it but it still is coming back.  I am running a dehumidifier in the garage which is never necessary here in San Diego as it is so dry.  Also, my washer & dryer are in the garage.  What would you recommend as my next course of action?  [Jan. 18, 2004]
       A. Because of the extreme amounts of rain your area has recently experienced, the ground is very saturated. Water is coming up through the garage floor by wicking upwards through the concrete. Most homes have no moisture barrier beneath their concrete slabs, an ineffective barrier, or a degraded barrier. Water penetration of a home through its concrete slab is an extremely big problem in California and worldwide. If the rest of your home is also on a concrete slab, you may have the same problem in your entire house. The wetness in the concrete will cause mold growth inside the walls of your home resting on the concrete.  Bleach is ineffective for killing mold. Please visit: Bleach Mold.  You should also mold test your entire home with do-it-yourself mold test kits [available from your local large hardware, home improvement, or safety store].

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