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Drying and Repairing Walls

Kenneth Hellevang, Extension Engineer

Remedies for Interior and Exterior Surfaces

Walls must be dry from the inside out before restoration, repainting or recovering can begin. Even when walls feel dry to the touch, the material inside the wall may be wet. Drying the inside of the walls may take weeks or even months. The total drying time will depend partially on the amount of dry air that can circulate through the studding and different wall materials.

Plaster and paneling can often be saved, but you still need to get air circulating in the wall cavities to dry the studs and sills. Wallboard soaked by dirty floodwater will need to be replaced. If the wallboard was damaged by clean rainwater, consider cutting a 4- to 12-inch-high section from the bottom and top of walls. This will create a "chimney effect" to speed up drying time. A reciprocating saw with a metal cutting blade works well for this task, but use only the tip of the blade and watch out for pipes, ductwork and wiring.

Guidelines for Wall Coverings and Insulation

Remove drywall, laminated paneling and plaster at least to the flood level. Warping above the water level often occurs with drywall and paneling, so more may need to be removed.

Plaster walls can sometimes be adequately drained by removing the baseboard and breaking out plaster and lath at the bottom of the wall. Later the baseboard can cover the opening.

Some paneling may be salvaged if allowed to dry slowly. Remove the baseboard from paneled walls and pry off the individual sheets. Prop them against the wall to dry. Don't allow them to dry in sunlight, which may cause warping.

Remove vinyl-covered wallpaper. It will restrict drying within flood-damaged walls.

Water-soaked insulation should be removed and replaced. It can hold water for months, causing odor and decay problems. While wet it has little insulation value.

Consider wainscoting as a restoration option if flooding is no higher than 3 feet above the floor.

Patching Plaster

Do not attempt to repair plaster until walls and inner walls (studding and insulation) are completely dry. If walls were flooded extensively, you may need to wait four to six weeks, or even several months, before attempting repairs.

Drywall compound is the preferred method for patching plaster. It comes in a variety of types with different drying times, shrinkage characteristics and consistencies. Read labels to select the type you need.

Repairing Exterior Siding

Dry wall cavities from the inside if possible. (See previous section.)

Remove small section of siding to check conditions on the reverse side. If crevasses are filled with silt, remove siding to water level and clean. Silt left in crevasses will trap moisture, causing mold, decay and peeling paint.

Check for cracked or warped siding. If only a few boards are warped or cracked, replace them individually.

Checking Sheathing

Sheathing is the material between studding and finish siding. Depending upon the type of sheathing, replacement may or may not be necessary.

Wooden boards should dry slowly and some will warp. Re-nail warped areas after they dry. Replace those that are too badly warped to salvage.

Sheathing board is usually absorbent and difficult to dry. Replace any that is disintegrating or separating.

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.

Related publications:

"Repairing Your Flooded Home," American Red Cross/Federal Emergency Management Agency, 1992.

Tips on Repairing or Rebuilding Your Disaster-Damaged Home, FEMA, 1981.


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