A friend writes us about a mold problem in their concrete floor that they found while remodeling their bathroom. They are wondering what steps they can take to remove the mold and prevent it from reoccurring.
This is a very common problem found in bathrooms. Whether the house is new or old the bathroom is one of the worst places in the home where mold will grow. It just seems pretty much eventual that over time there will be a problem but although it is common it doesn’t mean that every home will have the same level of damage.
In this case it seems that moisture that was trapped in the concrete slab floor probably worked in unison with the mastic to install the flooring to cause a condition where mold could grow pretty easily.
The first thing that you need to understand about this problem is that it is pretty much impossible to remove all moisture from concrete. Concrete is a porous sponge type material when it comes to moisture. It likes to absorb water and hold it. Although contractors can attempt to reduce the amount of ground moisture that gets into the slab by putting a plastic vapor barrier down before the concrete is poured you are never going to prevent all of the moisture from entering the slab.
Since Mold and Bacteria needs warmth, moisture and food to grow many building materials are perfect breeding grounds for them. Wood, Drywall, Concrete and basically anything that isn’t nonporous like steel or glass will allow growth. However I bet that you have probably even seen mold growing on glass in a bathroom before.
Unfortunately when the area is out of reach of household cleaners and disinfectants there is not a lot you can do to prevent this problem. This is especially true if the moisture is coming from below and not from above where you can control it.
One thing you might try is using a ceramic tile in the area instead of vinyl. But that is no guarantee. Another thing you want to do is address any leaks you might have immediately, such as a waste pipe leak under a slab.
How To Remove Mold And Bacteria In Your Home
The best product for killing mold and bacteria is bleach. If you look at most household cleaners or professional products that are made for killing bleach you will see that they contain bleach.
The trick when using bleach to kill mold is that you must treat the area long enough to kill the mold and bacteria. Every situation is different but the general rule is that a 5% sodium hypochlorite solution (bleach) should be allowed to treat the area for a minimum of 15 minutes. In real world conditions that time can be anywhere up to about an hour for full treatment.
This means that you keep the area wet with bleach by using a hand or pump sprayer for the entire time that it is being treated.
In many cases when the mold is killed it will change color from a dark green, brown or black to a yellowish color. This is a good indication that things are working.
Curing The Mold Problem
The most likely source of the mold problem was that the contractor that installed the flooring used a Mastic that was organic. There are a number of different types of adhesives used to apply flooring. Mastic as it is normally referred to is organic based so it provides the food for the mold to grow.
Remember that mold needs warmth, moisture and food to grow. By removing its easy food source you will possibly reduce its growth but mold is everywhere in the world and its on every surface in our homes too.
When ordering your flooring adhesive make sure that you select one that is mold resistant.
A best solution might be to install ceramic tile and use a thinset mortar because it is not an organic material it will not promote the growth of mold.
I strongly suggest that in areas such as a basement that you don’t install vinyl, carpet or other flooring and that you go with a ceramic tile. It can be more expensive but it will not cause the same problems in the end.
Final Note
Knowing your materials and how to use them best in all areas of your home will reduce problems in the long run.
Where mastic is a great choice for tile backsplash behind your stove it is not a good solution everywhere in the home.