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Disaster Relief: Home Cleanup and Renovation for Walls

Publication Number: IS1703
Updated: March 24, 2016
View as PDF: IS1703.pdf

Drying Inner Walls

Walls must dry from the inside out. The interior framing of walls should be allowed to dry thoroughly. Sometimes this takes weeks or even months. To release water and mud from walls, remove top and bottom strips of siding on the outside of the building. Drill several holes in walls near the inside floor line. Remove drywall from the floor to just above the waterline mark, and leave the space open until all of the wood dries out.

The total drying time depends partly on how much dry air can circulate through the studding (called “chimney action”). To provide for best chimney action, first consider the construction of the building.

Fire Stops or Cross Bracing

There are horizontal or diagonal braces between the vertical supports or studs. Cross bracing prevents chimney action between the studding. Cross bracing is not usually found in modern construction, except in two-story houses where it has been specified. To allow free air movement, remove interior or exterior wall covering wherever cross braces are located. To check for cross bracing or fire stops, put a stiff wire into the wall cavity.


Most types of insulation will be ruined if water-soaked. You will probably have to replace flood-soaked insulation.

  • Loose fill (such as vermiculite) settles to the bottom of walls. You can remove it as it dries. If you don’t remove it, loose fill insulation will create odors and eventually cause studding to decay.
  • Rock wool batting insulation also bunches and settles. If it is absorbent, it will create odors and could eventually cause studding decay.
  • Fiberglass batting also bunches but may not develop odors. Its insulating value will be greatly reduced if it is not thoroughly dry or if it settles and leaves areas at the top of walls unprotected.
  • Reflective surfaces (such as aluminum foil) sometimes lose their reflective ability, thus decreasing their insulation effectiveness. The material itself should be undamaged.

Wall Coverings and Finishes

  • Plaster takes weeks or even months to dry but may not be ruined by water. Old plaster, however, may disintegrate after being wet for a long time.

  • Sheetrock warps and disintegrates in water. Warping above the water level can also be expected. Drywall that has been submerged must be replaced.
  • Laminated paneling (plywood, masonite) separates and warps above and below the water level. The extent of damage depends on how long the paneling was in water and how quickly moisture is removed from the studding. Slow drying decreases the possibility of delamination.


  • Masonry dries slowly but will be undamaged except for possible cracking or settling. Open the inside walls to prevent mildew and decay of wooden supports.
  • With lapped siding (wood, asbestos, aluminum), remove strips or sections to dry insulation and studding. The type of sheathing determines drying rate. To prevent oxidation, make sure backing of aluminum siding is dry.

Sheathing (Material Between Studding and Finish Siding)

  • Wooden boards dry slowly, and some warp. If possible, nail warped areas again before they dry. Replace those that are too badly warped to salvage.
  • Sheathing board is usually absorbent and is difficult to dry. Some disintegrate or separate and must be replaced.
  • Plywood will probably separate and must be replaced. Marine plywood will not warp or separate but is generally considered too expensive to use in residential construction unless the building is subject to frequent flooding.

Cleaning Interior Walls

  • If walls have been flooded, hose them down while they are still damp to remove most of the mud and silt.
  • Scrub with a sponge and a warm, non-phosphate* solution or a commercial cleaner. Clean a small section of the wall at a time.
  • To get rid of the stench that often accompanies flooding, rinse with a solution of 2 tablespoons sodium hypochlorite laundry bleach (such as Purex or Clorox) to 1 gallon of water. Repeat the scrubbing and rinsing several times if necessary. You can also use household disinfectants such as Lysol. Follow directions on the container.
  • Work from the floor to the ceiling to prevent streaking. Rinse with an old bath towel wrung out in clear water. Overlap sections.
  • Clean the ceiling last.
  • Let walls dry thoroughly before repainting, repairing plaster, papering, or applying any wall covering. Allow at least 4–6 weeks’ drying time. Total drying time depends on weather conditions. You may need to remove baseboards or sections of the walls to dry interior studding and insulation (see Drying Inner Walls).
  • If mildew appears on walls, scrub with a disinfectant solution or a non-phosphate detergent.

*U.S. manufacturers have removed phosphate from laundry detergents. Special non-phosphate detergents may also be purchased at paint or hardware stores.

Information Sheet 1703 (POD-04-15)

Reviewed by Dr. David Jones, former Associate Extension Professor, Sustainable Bioproducts. From The Disaster Handbook - 1998 National Edition, University of Florida/Institute of Food and Agricultural Sciences SP 2431.

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