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Handling mold in residential buildings following hurricanes in Houston and Florida

Mani Skaria, PhD Professor, Texas A&M University-Kingsville (retired) Mani.skaria@uscitrus.com

Mani Skaria, PhD
Professor, Texas A&M University-Kingsville (retired)




Houston, Texas and the entire state of Florida was inundated with hurricanes, Harvey and Irma, in August and September 2017, respectively. Millions of homes and other buildings experienced extensive water damage affecting as many people.
Modern residential building walls have surface panels called drywalls, made of gypsum (calcium sulfate), pressed between thick sheets of paper. Drywall (also known as plasterboard or Sheetrock) are normally made with some additives that decrease mold growth. However, when drywalls are soaked in water for hours as in hurricane-associated floods, they do initiate mold growth soon.

Mold is also called mildew, its scientific group name is fungus (fungi, plural). There are many different molds that grow rapidly on wet drywalls. Many people use the name sheetrock, it is the name of a brand of drywall. A square foot of moldy drywall will produce millions of spores. Mold spores are small and easily air-borne. Mold spores cause allergy, asthma, infections of skin and tissues, including lungs. Some molds produce toxins (mycotoxins), some toxins are known carcinogens.

Floor carpets and carpet pads that are soaked in water also initiate mold growth. So also, structural woods, wooden cabinets, especially that are made of particle boards.

The AC closet in many homes are made with drywalls (inappropriately for cost cutting). The area below the AC unit is called, plenum. The plenum is an air-distribution area. It is always expected to be clean, dry, and dust-free. In a flood situation, the AC closets in the ground floor also get wet. With the airborne nature of mold spores, one of the first places that requires clean-up process is the AC closet.

Stachybotrys (black mold), Aspergillus, Alternaria, Chaetomium, Penicillium, Cladosporium, Fusarium are some of the commonly found molds in water-damaged buildings. Modern residential buildings in USA are more prone to mold growth because of the type of construction materials, compared to buildings in other countries such as India, or even in older homes built in USA.

Mold growth in residential buildings is not a new phenomenon. It has been with us always and will be with us forever. Managing mold after water-damage is more of an art and requires a rational approach than the biological sciences associated with mold growth and development. The first mention of a mold remediation protocol that I have seen is in the Holy Bible, Leviticus, Chapter 13: 47-59. The gist is: inspection (by the priest, the most learned person in the society), removal and cleaning of infected material, natural drying process, re-inspection, and discard the material if contamination persists. This was written centuries ago. You apply and modify the basics for today’s building materials and scientific knowledge. In the Bible, mold is referred to as mildew or leprosy of the building.

Some General Principles to Know
1. Mold (=Mildew) will grow on building materials after any water damage. Growth and development of mold happens very fast. It will produce millions of spores in a small area. These spores become airborne and cause allergic reactions and even infections.
2. The amount of work required for remediation far exceeds well-qualified service providers after the hurricanes in Houston and Florida. Therefore, be prepared to physically do or fully supervise some water damage control operations.
3. Drying the structural component of the building should start immediately after water damage.
4. After a Harvey/Irma type of water damage, attempting to dry and save materials such as floor carpet and padding is highly discouraged (see reasons in item 6 below)
5. Water damaged drywall is not recommended to be restored through any level of drying process.
6. The reason(s) for items 3 and 4 above are that:
Such items absorb water and initiate mold (=mildew) growth. Once mold growth is initiated in carpets, carpet pads, and drywall, it multiplies very fast and produces millions of spores that are very small and air-borne that can easily get into the respiratory system.
The kind of molds that are normally formed associated with water- damaged buildings are mostly: Aspergillus, Penicillium, Stachybotrys, Chaetomium, Fusarium, Alternaria, Cladosporium, etc.
Aspergillus are known to cause lung infections. Once the infection sets in, it is very difficult to remove with medication alone. Molds produce toxins, and toxins become air-borne.
7. Water damage remediation in the air condition closet should be done immediately to avoid circulation of mold spores and mold toxins throughout the building.
8. Treating drywalls with Clorox may be seen in some unscientific communications. Try not to save any drywall with Clorox treatments.
9. Young children, babies, elderly and immune-suppressive people should not be occupying a building when water damage remediation processes are in progress.
10. In addition to molds, water damaged buildings will often have infestations with cockroaches, mites and other arthropods. Physically remove all. Do not use cheap nose mask as protection. Invest in a well-fitting, full-face mask with glass to protect your eyes.
11. Painting over mold-affected drywall is a mistake.
12. Discard all moldy clothes. Wash and dry clothes that are water damaged but not moldy.
13. You may hear some people say that you can cut and remove only the water damaged drywall. Cutting drywall releases numerous particles into the air, which becomes a health hazard. You will be better off removing the whole sheet instead of cutting and patching it. The cost benefit of patching just a portion of the drywall pales in comparison to the hazards triggered by the airborne particles made in cutting operations. Avoid sentimentality on water-damaged and moldy materials. Containing the work area with plastic is a way to reduce air-borne particles.
14. Inexpensive moisture meters are available to check water-damaged drywalls, particle boards, etc.
15. Fans and air drying are ways to dry out water-damaged areas. You may have difficulty finding enough commercial dryers in Houston.
16. After the drying process, using dehumidifiers is recommended. Again, you may find scarcity of such machines.
17. Before reinstalling drywall and carpets vacuum and vacuum thoroughly.
18. You are directed to the USEPA rule that banned asbestos in building construction materials. Buildings constructed prior to 1990 may contain asbestos. Removal and discarding of asbestos containing materials require additional safety precautions.
Visit https://www.epa.gov/asbestos for more information.


The author has been involved in an official capacity, in many assessments on buildings that have suffered water damage in Texas. He taught a PhD level class on Mold, Buildings, and Human Health. He had served the state of Texas towards the development of a mold law, and consulted for schools, universities, hospitals, jails, and Texas state and federal government agencies, and several insurance companies in the country. He was one of the resource person appointed by the state of Texas towards developing a mold rules and regulations.
Disclaimer. The author has no business (consultation) interest or relationship with mold remediation companies. The information is shared out of a moral responsibility of a citizen with expertise and experience and once had a thriving consulting business for two decades. Readers are directed to verify the above facts with published directives on mold available through the Florida and Texas Department of Health and Human Services.

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