spraying for mold on floor joists

Spraying for Mold on Floor Joists: Pest Control

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“Has anyone noticed the new racket in town? Spraying for mold on floor joists.”

I get called in a lot to look at floor structures above crawl spaces, which have been inspected by pest control contractors who discovered either active or previous fungus infestation. Oftentimes the mortgage underwriter wants a home inspector or engineer to determine if there’s any structural damage as a result of this infestation. I always get copies of the Official Alabama Wood Infestation Report because I want to know what has been discovered (previous or active) and where it is located. I don’t want to spend an hour crawling around under a home looking for a patch of mold. Nearly every time I crawl beneath the home I end up asking myself, “What is going on here?” “The floor structure looks fine to me and the wood moisture content is less than 20%.” I glance down at the paperwork and see where the contractor sprayed a Borate solution on the joists to kill the mold. These costs are usually around $ 500.00. I’m starting to think this is money you may want your sellers to keep in their pocket. It might be worth getting a second opinion next time you hear the recommendation to spray for a hefty price.

Why Are They Spraying for Mold on Floor Joists?

First of all, mold is just one type of fungus. So it’s really fungus that we’re talking about because no one knows if the fungus on the floor joists is mold. Mold fungus is different from plants, animals and bacteria. Molds are eukaryotic micro-organisms that are decomposers of dead organic material such as leaves, wood and plants. The spores and hair-like bodies of individual mold colonies are too small for us to see without a microscope. When a lot of mold is growing on a surface, it often appears black, blue or green. The color of the mold is determined by the type and is influenced by the nutrient source, surface substrate and the age of the colony.

Mold needs water to grow. Without water mold cannot grow. Mold also needs a food source, oxygen and a temperature between 40 degrees and 100 degrees F. Since mold decomposes dead organic material (cellulose, hemi-cellulose and lignin) it loves to grow on wood floor structures in dark, moist crawl spaces. Molds secrete digestive fluids that decompose the substrate, making nutrients available. Molds prefer damp or wet material. Some molds can get moisture from the air when the air is very damp, that is when the relative humidity is typically above 60%. The high humidity makes enough moisture available to make surfaces damp enough for mold to grow.

Mold can grow by extension of hyphae that are like tiny root hairs. In this way, a small colony of mold can expand to cover many square feet of material. Mold can also make spores that are like very small seeds. Spores can survive conditions that are too sunny, hot, cold, dry or wet for mold to grow. When spores are released they can be carried by air or water to new locations—such as into the crawl space through the perimeter foundation vents. When spores land on a damp surface that has food (wood) and oxygen available, and if the temperature suits them, they will start to grow.

It is important to realize that mold spores are ubiquitous in nature and are present everywhere, in outside air as well as indoor air – unless very special precautions are taken to remove or kill them such as in clean-room and hospital operating theaters. Wherever there is decaying organic material (leaves, mulch, and wood) mold and mold spores are also present. Everyday, since we were born, we have been exposed to airborne mold spores from outdoor sources, sometimes at high concentrations. It is almost impossible to create a mold free space or to keep a space mold free. What we can do – and should do – is to control the amount of moisture and hence the amount of mold in our indoor environments. Too much mold can affect the health of you and your family. In addition, mold can damage or destroy building materials such as the wood in our homes.

North Alabama is located in the SE United States, which is known to have a warm humid environment. Whenever we ventilate our crawl spaces, we are introducing fungus spores and warm humid air. If there are air conditioning ducts in the crawl space (a common situation), the temperature inside the crawl space stays around 70 degrees, while outside, in the middle of July, the temperature is 90 degrees–and the humidity is 80%.. Whenever this hot, humid air enters the crawl space, which stays at a constant 70 degrees due to the air conditioner duct leakage, the hot humid air gives up it’s moisture while dropping in temperature to 70 degrees. This water condenses on cool objects such as the air conditioning ducts and the cool wood floor system. This wets the wood floor and this allows fungus to grow. This occurs all summer long during the air conditioning season. Then during fall, winter and spring, the humidity beneath the home drops along with the outside cooler air, and the wood floors beneath the home dry. The fungus has now lost its moisture source, so it goes dormant. It doesn’t leave, it just goes dormant, only to be rejuvenated again once the condensation cycle starts over or humid conditions develop in the crawl space due to water seepage or plumbing leaks.

When pest control contractors crawl beneath the home, they always see floor joists with surficial fungus growth. Whenever, they see lots of surficial fungus growth, a sign of a humid crawl space, they recommend spraying. I say they should always carry an electronic moisture meter and they should always probe the floor structure to check for the wood moisture content. If it is below 20%, then there is no active fungus. The joists may be stained or painted with light fungal growth, but it is dormant fungus. It can be wiped clean with soap and water. It doesn’t need a $ 500 shower of Borate solution.

So, don’t ever agree to pay for spraying for mold on floor joists unless the pest control contractor insists the moisture content of the floor joists are 25% or higher. Thirty percent moisture content is saturated wood, so when the joists get this wet, you have a serious problem and need to be installing a crawl space encapsulation system.

Don’t hesitate to contact us for any of your inspection service needs and feel free to ask us questions!

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