Water-damaged walls can be repaired, but they must be dry from the inside out before you start restoring, repainting, or recovering them.

“Even if the walls feel dry, the material inside the wall may be wet,” says Ken Hellevang, North Dakota State University Extension Service flood expert. “Drying the inside of walls may take weeks or even months.”

The drying time will depend partially on the amount of dry air that can circulate through the studding and wall materials.

Plaster and paneling often can be saved, but you need to get air circulating in the wall cavities to dry the studs and sills. Remove drywall, laminated paneling and plaster to at least the level the floodwaters reached. You may need to remove more drywall and paneling because it can warp above the water level.

You may be able to drain plaster walls adequately by removing the baseboard and breaking out plaster and lath at the bottom of the wall. The baseboard can cover the openings later.

You may salvage some paneling if it is allowed to dry slowly. Remove the baseboard from the paneled walls and pry off individual sheets of paneling. Prop the sheets against the wall to dry. However, don’t let them dry in sunlight because they could warp.

Wallboard soaked by dirty floodwaters will have to be replaced. If clean rainwater damaged the wallboard, you can cut a 4- to 12-inch-high section out of the top and bottom of the walls. This will create a “chimney” effect to speed up the drying time. A reciprocating saw with metal cutting blades works well for this, but use only the tip of the blade and watch out for pipes, ductwork and wiring, Hellevang says.

If your walls are covered with vinyl-coated wallpaper, remove it because it will restrict drying in flood-damaged walls.

Remove and replace water-soaked insulation because it can hold water for months, causing odor and mold problems.

Do not try to repair plaster until the walls and studding are dry. Drying may take four to six weeks, or even several months, if the walls were flooded extensively. Drywall compound is the preferred material for patching plaster. It comes in a variety of types with different drying times, shrinkage characteristics, and consistencies. Read the products’ labels to select the type you need.

When repairing your home’s siding, dry the wall cavities from the inside if possible. Remove small sections of siding to check its condition on the reverse side. If crevasses are filled with silt, remove the siding to the level the water reached and clean out the crevasses. Silt left in crevasses will trap moisture, causing mold, decay and peeling paint.

Check for cracked or warped siding. Replace individual boards if only a few are warped or cracked.

You also need to check the sheathing, which is the material between the studding and siding. Sheathing board usually is absorbent and difficult to dry, so replace any that is disintegrating or separating.

Wooden sheathing should dry slowly, and some will warp as it dries. Renail warped boards after they are dry. Replace any boards that are too badly warped to salvage. Plywood sheathing probably will separate and should be replaced. Marine plywood won’t warp or separate, but it generally is too expensive to use in residential construction unless the home is subject to frequent flooding.

Source: North Dakota State University

Aspen Environmental Services does flood damage repair and reconstruction and recommends the use of experienced, licensed professionals after flood damage to prevent or remove mold and avoid other dangers. Call them at 800.931.MOLD (6653) or email [email protected].