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Dry Before Restoring Flood-damaged Buildings

Flood-damaged buildings need to be dried before they can be repaired.

“Wood submerged in water will absorb a large amount of water,” says Ken Hellevang, North Dakota State University Extension Service flood expert. “Rebuilding too quickly after a flood can cause continuing problems, such as mold growth, insect infestations and deterioration of the wood and wall coverings.”

Wood may take weeks to dry. The drying time will depend on the initial moisture content and drying conditions. Wood should have a moisture content of less than 15 percent before you replace drywall, paneling or other coverings.

Using a moisture meter is the best way to determine if the wood is dry, according to Hellevang. Most county Extension Service offices have moisture meters you can check out.

To dry a building, use a sump pump, mops, fans and/or natural ventilation. Once the structure is dry:

  • Inspect laminated woods, such as plywood, that have been immersed in water to be sure laminations still are firmly bonded together. Check nails to determine whether they still are firmly in place.
  • Remove silt and mud from floors. Wood floors that have absorbed a lot of water could be buckled. Do not repair them until they are fully dried. Pulling some of the flooring back into place with nails may be possible. Plane and sand the floors as needed to remove humps. This may not get the floors into condition to look good uncovered, but they will be smooth enough to serve as a base for a new covering.
  • Remove any insulation that was wet. Floodwaters often will leave absorbent material with a foul odor that is difficult to remove. When checking the insulation, expect it to have been wet above the high-water level because of the material’s wicking action.
  • Replace any drywall. However, interior sheathing in out-buildings such as barns usually will be wood, which can be removed, dried and reused.
  • After removing interior sheathing and insulation, inspect the wall studs, sills and plates for structural damage, and repair or replace damaged components.
  • To replace insulation in the walls, place a 4-mil or 6-mil polyethylene vapor barrier on the warm side of the insulation according to local building recommendations and then install interior drywall or sheathing.
  • Inspect wiring and plumbing for damage. Electrical outlets, switches, sockets and breaker or fuse boxes generally need to be replaced. Check local electrical codes. Do not turn on the power to a flood-damaged structure until a qualified person has inspected it.H
Here is advice for flood-damaged farmsteads:
  • Disconnect equipment that was immersed in floodwaters, such as milking equipment, grain augers and ventilation fans, from the power source and completely disassemble and thoroughly clean it to remove grit or other contaminants.
  • Do not run electric motors that were submerged until a qualified person has reconditioned them. This means air conditioners, furnaces, appliances, feed augers, fans and other equipment may not be available for several days.
  • Clean, dry and lightly oil all metal tools to prevent rusting.
  • Recondition power tools before using them because floodwaters leave deposits in motors that may cause electrical faults, creating a safety hazard.

Also, you may need special cleanup and disposal measures if fuel or chemicals spilled during the flooding or have water damage.

For more information, view these videos: www.ag.ndsu.edu/flood/home/cleaning-up-your-home-after-flooding-video and www.ag.ndsu.edu/flood/home/using-a-moisture-meter-before-rebuilding-video, or visit www.ag.ndsu.edu/flood or www.extension.org/Floods.

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