Six Tips for Drying Out a Flooded Building

F. Mitchener Wilds, supervisor of the Restoration Services Branch of the North Carolina State Historic Preservation Office, has been involved in restoring historic buildings for many years. He has provided tips for drying out water-damaged buildings. His full list, which is available here, is excerpted below, with his permission.

After a catastrophic flood affects your home, the process of restoring and remediating the damage can seem daunting. Once a home or building has been exposed to floodwaters, it’s important to dry it out in order to assess damage and plan for repairs and restoration. Floodwater affects a building in three ways:


  1. Water causes direct damage to materials. Wallboard disintegrates; wood can swell, warp and rot; electrical parts can short out, malfunction and cause fires or shock.
  2. Mud, silt and other contaminants in the water (think sewage) make everything dirty and unhealthy.
  3. Dampness promotes the growth of moisture-related mold, mildew and fungus that leads to dry rot.

Rely on Natural Ventilation and
Air Circulation

Drying a building out can be time-consuming, as the best approach is to allow natural ventilation and evaporation to do the work. It’s better for the building, since rapid drying using forced hot air can cause irreparable damage to some building features.

Start at the Top

When drying out a building, your efforts should start at the top, in the attic. Begin by opening windows and vents to allow fresh air to circulate. If your electrical system is safe and you have an attic fan, turn it on. Then remove any water-soaked items stored in the attic. The weight of water-soaked boxes can cause the ceilings below to crack. Also remove and properly dispose of any wet insulation. After becoming wet, most insulation is ineffective, and it will hold moisture for a long time and create high moisture conditions that over time will damage metal, masonry and wood.

Once done in the attic, begin moving down through the structure. Open windows in all rooms, even if there is no evidence of moisture retention. If the windows are swollen shut, remove the inside stop bead to free the window sash. Window fans will help draw fresh air through the building, helping to dry out cavities between interior and exterior walls. Remove wet carpets, furniture and water damaged household furnishings from the house. Drying out these items in the house only adds to the moisture level within the house. Remove sheet vinyl or linoleum flooring to allow for maximum evaporation. Any features removed during the cleanup, such as trim, should be labeled and saved for later reinstallation.

Pay Careful Attention to Ceilings

As you enter each room, inspect the ceilings carefully. Wet plaster and sheetrock can be very heavy, and as such can be a hazard. Be aware of bulging ceilings that may hold trapped water. Poke holes at the edges of any ceiling bulges to release the water, and collect it in buckets for disposal.

If sheetrock has been exposed to water for less than two hours, it can probably be repaired. Otherwise it will be saturated by contaminated water and require complete replacement. Plaster dries out much better than sheetrock, but its durability depends on the plaster mix, the original application, the degree of water saturation, placement and the type of lath used. Plaster over metal lath is likely to require replacement. Wood lath may expand if saturated, causing the plaster keys to break. Check for loose plaster and plan to reattach it using plaster washers. Plaster ceilings can be temporarily shored by using 2x4s nailed together to form a “T” and using the top of the T to press plywood against the ceiling.

Get Water Out
of the Walls

You can drain water from within the wall cavity by removing the baseboard and drilling holes through the plaster or sheetrock several inches above the floor. Use cordless or hand drills to avoid electrical shock and be careful to avoid wiring within the walls. Remove any wet insulation by removing the baseboard, and allow the wall cavity to dry out thoroughly.

Take it Slow
with Wood Floors
and Features

Wash down wood features — including trim, doors, mantels and stairs — to remove mud and silt. Mold and mildew can be removed using a weak solution of bleach and water or commercially available disinfectant. If wood floors are coated with mud, wash them down with fresh water. The floorboards might begin to warp as they dry, but further drying might bring them back to their original shape. Using weights or shoring on the wood floors during the drying process may reduce severe warping and buckling. Remove vapor barriers and insulation from beneath the floor to allow for complete air circulation. Do not use heat, air conditioning or other forced air to dry wood floors. Rapid drying can promote cupping of the floorboards, as the top surface dries out faster. Drying out wooden floorboards may take several months.

Don’t Pump Out the Basement Right Away

It might sound counterintuitive, but if your basement is flooded, do not rush to pump it out. Draining the basement while the surrounding ground is saturated may create uneven pressure on the basement walls and floor and cause cracking or collapse. Once floodwater surrounding the house has receded, lower the water level in the basement by two or three feet, mark the water line and wait overnight. If the basement water level rises, then it is too early to fully pump out the basement. If the water level remains stable or drops, then pump out another few feet and again check the water level overnight. Continue this process until the basement is free of water.