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Take steps to prevent, remove mold from flooded homes

News Release Distributed 09/06/12

After a flood, mold colonies can start to grow within two to three days. The key to preventing mold is to act fast and get things clean and dry, according to LSU AgCenter housing specialist Claudette Reichel.

To prevent mold growth after flooding, Reichel recommends that you do the following:

– Remove wet carpeting and pads right away, as well as wet draperies and upholstery.

– Cut into wallboard and remove all wet and damp insulation promptly – even if wallboard appears to be dry. Wet insulation will stay wet far too long, leading to the growth of hidden, unhealthy mold and fungi inside the walls.

– Clean with non-phosphate detergents – any phosphate residue is mold food. If you disinfect, follow directions carefully and never mix bleach with ammonia or acids (vinegar). Disinfectants can kill molds but do not prevent new growth on damp materials.

– Do all you can to speed the drying of subfloors, slabs and wall framing before replacing insulation, wallboard and flooring. Use air conditioning or heaters, fans and, better yet, a dehumidifier. Water-damage restoration contractors with special equipment (dehumidifying blowers) can provide the fastest drying.

– Test the moisture content of studs and sheathing using a moisture detector before replacing insulation. Wood should drop below 20 percent moisture content before you close the wall.

– Do not use vinyl wallpaper. It prevents further drying to the inside.

Reichel said to clean up mold, follow these steps and refer to more detailed information available online at

– Minimize your exposure during clean-up. People are mainly exposed to mold by breathing spores or fragments and can also be exposed through skin contact. Wearing gloves and a respirator that can filter mold spores (N-95 or better) is recommended.

– Isolate work areas and ventilate to outdoors. Disturbing mold colonies can cause a massive release of spores, so seal off the contaminated area from the rest of the house. If power is on, use a fan to exhaust air to the outdoors.

– Remove and discard moldy material. Porous moldy or sewage-contaminated materials should be removed, bagged and thrown away – including gypsum wallboard, insulation, plaster, carpet/carpet pad, ceiling tiles, processed wood products and paper. To minimize the spread of spores, cover moldy material with plastic to contain spores before removing and discarding it. Even if not moldy, all wet fibrous insulation and other materials that are unlikely to dry quickly should be removed and replaced.

– Clean surfaces. Surface mold on non-porous materials such as hard plastic, concrete, glass, metal and solid wood can usually be cleaned. Cleaning must remove, not just kill, the mold because dead spores can still cause health problems.

– After cleaning, you may choose to use a disinfectant to kill any mold missed by the cleaning, but it is not a substitute for cleaning. In the case of sewage contamination (including floodwater), disinfection is recommended. On colorfast, non-metal surfaces, you may disinfect with a solution of 1/4 to 1/2 cup bleach per gallon of water. Do not use this in the air system. Milder, less-corrosive disinfectants include alcohols, disinfecting cleaners and hydrogen peroxide. Always handle chemicals with caution, never mix bleach with ammonia and test on a small area.

– Consider treating wood with borate. While walls and subfloors are exposed is a great time to treat them with a penetrating borate solution to provide safe protection from termites and decay. The coating may also help to deter mold growth during the drying time.

– Speed dry. Dry all wet materials as quickly as possible. Use air conditioning or heat with fans and dehumidifiers, if possible. New mold colonies can form in as little as three days if materials stay wet. Wood and other materials that look dry can still be wet enough to support regrowth.

– Remain on mold alert. Continue looking for signs of moisture or new mold growth. If mold returns, repeat cleaning and consider using speed drying equipment and moisture meters. Regrowth may signal that the material was not dry enough or should be removed. Rebuilding should wait until all affected materials have dried completely.

– Do more than restore. You can reduce future damage and ordeal by restoring your home with flood-resistant materials and elevating equipment where possible. Consider ceramic or solid vinyl tile flooring and wall assemblies that can be washed and dried with solid wood studs, plywood (no OSB), closed cell foam insulation and paperless drywall with latex paint or removable wainscoting.

See and learn more about hazard-resistant housing at and by visiting LaHouse Home and Landscape Resource Center in Baton Rouge. Find more storm recovery publications at or visit your local LSU AgCenter office.

Johnny Morgan

Last Updated: 9/6/2012 10:06:58 AM

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