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Clean Wet Buildings Quickly, Safely

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Flooding and seepage from saturated soils mean many North Dakotans will be faced with cleaning wet buildings this spring.

Ken Hellevang, a North Dakota State University Extension Service engineer and professor in NDSU's Agricultural and Biosystems Engineering Department, has these tips to help the cleanup go more smoothly and safely:


* When using wet/dry vacuums and other cleaning equipment, use an extension cord with a ground fault circuit interrupter or install a ground fault circuit interrupter in electrical circuits. Do not stand in water when using electrical equipment.

* Sewer backup contains extensive biological contamination, so clean carefully.

Wear boots, gloves and other protective gear. Overland flooding also may contain some biological or chemical contamination, so wear personal protective clothing.

Porous materials such as carpet or drywall that can absorb water need to be discarded if they were exposed to sewer backup or other water with biological or chemical contamination.

* Wet materials will mold in one to three days, depending on temperature, so cleanup and drying need to be done quickly. Mold in buildings is a human health hazard. Mold must be removed, not just killed, by using a biocide to eliminate the hazard. Open at least two windows for cross-ventilation to remove moisture in the house or use a dehumidifier. Adding heat without exhausting the air just creates a warm, humid environment and does not aid drying. Use fans to circulate air across damp surfaces to help the material dry.

* Clean and dry carpets and rugs quickly. For health reasons, discard carpet if it was exposed to sewage or mold growth occurred. Hot-water extraction is the best way to clean soiled carpets, so have them cleaned professionally or rent the equipment to do it yourself. To clean small amounts of carpet or rugs, take them outside and hose them down. Use a disinfecting carpet cleaner to clean them thoroughly. Dry the carpet or rugs and floor rapidly and thoroughly before replacing the carpet. Replace the padding; do not try to dry it. Use a moisture meter to assure that a wood floor is dry before replacing the carpet or rugs.

Before placing carpet on concrete, tape a 3-foot-square plastic sheet on the concrete for a couple of days to make sure moisture vapor is not coming through the floor to create damp conditions conducive for mold growth.

If the carpet can't be removed, dry it within 48 hours of when it became wet, using a wet/dry vacuum, dry outdoor air and/or dehumidifier to minimize mold growth. Use fans to circulate air above and underneath the carpet. Unless the carpet is very thin and does not have a pad, such as an indoor/outdoor carpet, lifting it to expose both sides for drying is very important. Mold growth likely will occur unless the carpet can be dried within 24 to 48 hours, depending on temperature.

* Clean and disinfect nonporous materials. Scrub surfaces with hot water and a heavy-duty cleaner. Then disinfect the materials for biological contamination with a solution of 1/4 cup of chlorine bleach per gallon of water or a product that is labeled as a disinfectant to kill germs. Follow label directions. Don't mix cleaning products because a combination of chemicals can give off toxic fumes.

* Dry ceilings and walls. Typically, removing and throwing away water-soaked wallboard is necessary because it loses its structural integrity and drying it may not be possible before it becomes moldy. Damp wallboard that does not contain insulation needs to be dried rapidly by circulating air onto the damp wall. It must be dried within a couple of days to prevent mold growth. Water will wick up drywall a couple of feet above the waterline. Frequently, you will need to open a wall to dry it rapidly. If the wall contains insulation, the wall needs to be opened and the insulation removed. The insulation retains moisture, and the paper on the interior of the wall will become infested with mold before it dries. Plaster and paneling may be saved, but air must circulate in the wall cavities to dry the studs and sills.

* Clean appliances. Use a heavy-duty cleaner and hot water, then a bleach solution, to clean surfaces. Recondition or replace electric motors that were submerged in water.

* Hire a professional to replace or recondition electrical wiring and equipment.

Breaker panel boards, breakers, fuses, receptacles, switches, light fixtures and electric heaters that were submerged must be replaced. Electrical wiring also may need to be replaced.

For more information, visit the NDSU Extension Service website on coping with flooding at and your local NDSU Extension Service office.