Remove, prevent mold in flooded homes

(03/18/16) BATON ROUGE La. – A flooded home can harbor mold colonies after the waters recede.

“Mold colonies can start to grow within two to three days, so the key to preventing mold is to act fast to get things clean and dry, said LSU AgCenter housing specialist Claudette Reichel.

Reichel offers several tips prevent mold growth after flooding:

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

– Cut into wallboard and remove all wet and damp insulation, even if the wallboard appears to dry.

“Wet insulation will stay wet far too long, leading to the growth of hidden, unhealthy mold and decay fungi inside the walls,” Reichel said.

– 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, such as vinegar,” Reichel said. “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, heaters, fans and, better yet, a dehumidifier,” she said.

Water-damage restoration contractors can use special equipment such as dehumidifying blowers to hasten drying.

Test the moisture content of studs and sheathing with a moisture detector before replacing insulation, Reichel said. Wood should be below 20 percent moisture content by weight before closing a wall.

“Do not use vinyl wallpaper,” Reichel said. “That would prevent walls from drying further.”

If mold in present, it must be cleaned up, she said. More detailed information is available online at .

“Minimize your exposure to mold during cleanup,” Reichel said. People are mainly exposed to mold by breathing spores or fragments, but they can also be exposed through skin contact.

Wear gloves and a respirator rated N-95 or better that can filter mold spores to ensure safety.

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.

Moldy or sewage-contaminated porous materials should be removed, bagged and thrown away, Reichel said. This includes 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 and discard it.

Even if not moldy, all wet fibrous insulation and other materials that are unlikely to dry quickly should be removed and replaced, she said.

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,” Reichel said.

“After cleaning, you may choose to use a disinfectant to kill any remaining mold, but it is not a substitute for cleaning,” she said. Disinfecting is especially important in the case of sewage contamination, including floodwater.

Colorfast, nonmetal surfaces can be disinfected with a solution of 1/4 to 1/2 cup of bleach per gallon of water, but do not use this in an air-handling system, Reichel said. Milder, less-corrosive disinfectants include alcohols, disinfecting cleaners and hydrogen peroxide.

“Always handle these materials with caution, never mix bleach with ammonia, and test any formulation on a small area,” she said

When 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.

“Remain on mold alert,” Reichel said. “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.

Homeowners can reduce future damage and ordeal by restoring their homes with flood-resistant materials and elevating equipment where possible. “Consider ceramic or solid vinyl flooring and washable wall assemblies with solid wood studs, plywood, closed-cell foam insulation and paperless drywall with latex paint or removable wainscoting,” Reichel said.

More information about hazard-resistant and high performance housing at is available at and by visiting LaHouse Resource Center near the LSU campus in Baton Rouge.

3/18/2016 3:25:55 PM
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