Mold In A New Home

By Stephen Andrews

I was called out to test for mold in a detached one story single family dwelling. The owner was a brilliant engineer specializing in coal burning power plants. During his career he had consulted on projects in seven different countries. He and his wife had recently retired to Marietta, Georgia. They had chosen a retirement community designed for and restricted sales to people fifty-five and older.

Although their home was less than two years old, his wife began to suffer from several health issues and she suspected they were mold symptoms. She would begin to feel better when she was away from home for a few days but her symptoms would return after being for several hours. She had been diagnosed with mold allergies and was allergic to Penicillium.

I made a quick visual inspection of the outside before knocking on the door and introducing myself. The house was built on a slab and the first thing that came to my attention was the driveway ran parallel to the home about seven feet from the front of the home. The ground sloped away from the driveway, toward the house. The grade of yard at the house slab was almost level with the floor. On the other three sides of the home the ground was only two to three inches below the slab, barely sloping away from the home. A good rainstorm could easily flood this place. Even under normal conditions, excessive moisture could accumulate in the concrete slab. Depending on what floor coverings were used and how the humidity was controlled inside the home, the problem could become much worse and conditions for mold growth could be created.

There were several observations that immediately brought up red flags. To start with, the grade around the floor slab was inadequate and could lead to flooding. When I entered their home I noticed that the thermostat was set to keep the temperature in their house fairly warm. This meant that their air conditioner was not running enough to control the humidity in their home. I also discovered that the hardwood flooring was glued directly onto the concrete slab. This kind of installation would expose the wood to the moisture rising from the concrete. To make it even worse, the wood floor had an acrylic finish, which acted as a moisture barrier, preventing the wood from drying as moisture in the concrete tried to migrate through the wood into the atmosphere.

Since there was no visible mold I decided to take a couple of air samples inside and a sample outside for comparison. Several moisture measurements were taken in various locations in an attempt to determine if conditions existed to sustain mold growth. The laboratory results indicated unusually high levels of Penicillium/ Aspergillus and moisture measurements in the floor indicated levels of moisture in the concrete ranging from 18% to 34%. When I discussed the result with the homeowners, the Mrs. indicated she was allergic to Penicillium. The homeowner decided to take the investigation to another level and with his background in engineering and project management he attacked the project with a vengeance.

The initial findings led me to believe there was mold growth beneath the hardwood flooring. In a few areas there appeared to be very slight cupping in the floor further supporting the idea of elevated moisture under the hardwood flooring. In 2007, residents of Atlanta had been suffering through the worst drought in over one hundred years so this was somewhat perplexing.

The homeowner drew a scale drawing of his floor plan and identified fifty-five locations he wanted moisture measurements taken. Over a period of six months, he had me take moisture measurements in each of the locations four times. He even purchased a different brand moisture meter and had me take measurements with his meter in the same locations and time so he could compare the variance between the meters.

At the end of testing period it was decided to take up some of the flooring for mold tests. They had moved out of their home a couple of months prior because the Mrs’. mold symptoms were not going away. I sent one bulk sample to a lab for tests and they concluded no mold growth was present. I could not accept that there was no mold growth because conditions were present to support growth and there were small black specks on the bottom side of the hardwood that looked to me like mold. I took the sample to a different laboratory and had them incubate it for seven days. This time test results showed Penicillium/ Aspergillus present. I have worked with several different laboratories and find results vary substantially from laboratory to laboratory. Sampling methods are fairly straightforward and are easy to learn. They don’t vary much from inspector-to-inspector but laboratory work is tedious and requires attention to detail. I feel inspectors should try three or four laboratories by double sampling and sending the results to different laboratories until they feel comfortable in choosing a lab.

I believe the mold problem resulted from a combination of three issues:

  1. Excessive moisture in concrete resulting from grade levels and lack of drainage around the slab and an incomplete vapor barrier beneath.
  2. The acrylic hardwood finish forming a vapor barrier on top of the hardwood restricting the drying process of the concrete below;
  3. and high humidity levels inside the home that slowed drying.

In the end, because of the homeowner’s professional skills and my refusal to except the first laboratory’s test results, they were able to force the builder into buying the home back, allowing the couple to find a home with healthy air, thereby providing an escape from the plaguing mold symptoms.

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