The floodwater may have left the building, but a wet mess remains. Before you can rebuild your home, you have to dry out the wood framing, say specialists from Iowa State University Extension.
“Just cleaning up isn’t enough,” said Mary Yearns, ISU Extension housing specialist. “Walls that have gotten wet must be completely dried out before you rebuild. Otherwise mold will grow in wet walls that are closed up before they dry.”
Tear out dry wall or plaster to the flood line, and discard any wet insulation, Yearns said. Wall cavities that are moldy must be cleaned. Then allow sufficient time for all the framing lumber to become thoroughly dry. Check the wood moisture content weekly until it drops below 20 percent. If electricity is available, use fans and open windows to let in dry outside air and exhaust the damp inside air.
Deal with Mold
Mold can be a health hazard and must be removed before the house can be lived in, added Dean Prestemon, retired ISU Extension wood products specialist. He suggested wearing protective clothing when cleaning up mold, including boots, gloves and an N-95 or HEPA mask.
“These types of mask will have two straps. A one-strap mask likely isn’t effective in removing mold spores,” Prestemon said.
For most non-porous surfaces, clean first with normal cleaning agents — detergents and soaps. Then sanitize with chlorine bleach — one-half to 1 cup chlorine bleach to 1 gallon of water.
“Diluting the bleach in this manner is more effective than higher concentrations,” Prestemon said. “This is a sanitizing step after you have cleaned the material. The surface needs to stay wet with the bleach solution for about 10 minutes so that it can be effective. Chlorine bleach will kill the mold that is on the material. Then let the surface dry.” Chlorine bleach does not prevent new mold spores, always present in the air, from re-establishing if the surface is damp.
Wood is a semi-porous material, but it can be cleaned, Prestemon continued. To remove mold and mildew from wood framing, first clean the wood with detergent and water and heavy-duty scrubbing. Then sanitize the wood with one-half to 1 cup of chlorine bleach per gallon of water.
For more information on removing mold from a flood-damaged home, download a free copy of Storm Recovery Guide (SP 327) from ISU Extension’s Online Store, https://www.extension.iastate.edu/store/. This document was created by Louisiana State University AgCenter and has been adapted for use in Iowa by ISU Extension.
Let the Wood Dry
After removing the mold, the next step is to let the wood thoroughly dry, Prestemon said. He recommends getting the wood to below 20 percent moisture content. “If you get the wood to below 20 percent moisture content and keep it at that level, you won’t get mildew growth. But you have to open up the structure — remove the drywall or the plaster — and leave it open for two or three weeks or longer.”
If the wood framing isn’t dried to below 20 percent moisture content, consumers are taking a big risk if they rebuild, Prestemon said. Mold may not grow on the wood framing if the wood is above 20 percent moisture content, but the paper backing on the new drywall could pick up moisture from the wood, and the new drywall could mold.
Consumers can use moisture meters to determine the moisture content of wood framing, Prestemon said. The most common type of moisture meter (also referred to as resistance meter) measures direct current conductance between two metal pins inserted into the wood, which is then correlated with wood moisture content. When using a moisture meter, follow the instructions carefully. Instructions are specific to the meter.
ISU Linn County Extension offices and Linn County Public Health Department have moisture meters that can be borrowed by flood victims. To reserve a meter, call Linn County Extension at 319-377-9839 or Linn County Health Department at 319-892-6000.
How can you tell if your basement is really dry?
For those on the edges of the flood who received small amounts of water in the basement, it may be tempting to think it is dry and move ahead to put down carpet and bring back furniture. Be careful not to move to soon. According to Linda Bigley, Linn County Extension Director, a cement floor may look dry but because the ground is still saturated moisture will continue to move through the concrete.
A tip from Extension staff who worked with flood recovery in North Dakota is to cut a 3 foot square of heavy plastic and use duct tape to seal it to the floor, wait 24 hours and look to see if moisture has condensed on the plastic; if there is condensation, do not lay carpet or bring in furniture. The same technique can be used to check for moisture in walls.