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Dry out before rebuilding

April 23, 2019 GMT

After clean-up of flooded homes and buildings, do not be in a hurry to repair or rebuild. Wood and other surfaces need to dry first.

Rebuilding too quickly after a flood can cause continuing problems such as mold growth, insect infestations and deterioration of wood and wall coverings, according to Kenneth Hellevang, Extension Agriculture Engineer with North Dakota State University Extension.

The steps to cleaning include removing debris, mud and flood damaged items. Then cleaning surfaces with a non-phosphate soap to further remove dirt and organic matter, rinsing, and allowing to dry. Next, applying a disinfectant, such as unscented bleach or a quaternary ammonium compound, according to label direction.

Read and follow all label directions for mixing and using the disinfectant and follow all precautions listed. NEVER mix a disinfectant or cleaner with any other product. NEVER mix chlorine bleach with ammonia or vinegar, as toxic gasses are produced.

For information on how to safely and correctly complete the above steps, see our NebGuide “Entering and Cleaning Flooded Homes” found at www.flood.unl.edu under homeowners information.

Where mold growth has already begun and is extensive, covers more than a 10 foot by 10 foot area, professional mold remediation is recommended.

After cleaning and disinfecting, the final step is drying out. This is critical to preventing continuing problems like mold. The following information is from the NDSU publication ‘Dry out Before Rebuilding’ by Dr. Hellevang.

Wood submerged in water will absorb a large amount of water. It may take weeks for the wood to be adequately dry to do repairs or close a wall that needed to be opened for drying.

The drying time will vary depending on the initial moisture content and drying conditions. To know if wood is dry, test it with a wood moisture meter. Nebraska Extension offices have wood moisture meters available for check out. Call the Platte County Extension office at 402-563-4901 to ask about these.

Wood should have a moisture content of 15 percent or less before drywall, paneling or other coverings are placed on the wood. If a contractor is doing the work, homeowners should have the contractor verify with a meter that the wood is dry.

Ventilation can be used to aid drying. Know that mold growth has likely occurred and wearing personal protective equipment, like an N-95 air filter mask, is highly recommended whenever working in flood impacted homes.

To aid drying, provide an entrance and exhaust opening for air to promote cross-ventilation. Place a fan in a window or door with the fan to the outdoors. Seal the rest of the opening with cardboard, plywood or blankets so the fan creates a vacuum. Use fans to circulate air over wet surfaces. Face fans into corners or other hidden areas.

Heat increases the moisture-holding ability of air. If possible, use your furnace or large heaters to heat the air. Small space heaters will have little effect. As wood gets drier it may be helpful to heat the house for a few hours, then ventilate to exchange moist air with dry air.

A dehumidifier can be also used. Dehumidifiers function most efficiently at warm temperatures. At 80 degrees and 60 percent relative humidity, most dehumidifiers will remove one to two pints of water per hour from the air.

Source: North Dakota State University and Nebraska Extension