Limit Damage - Prevent Wicking
Damage from shallow floods is typically not confined to the area that was touched by floodwater, but includes areas that were wet by water wicking - creeping up the wallboard (commonly called sheetrock) and other porous building materials. You can reduce the damage from shallow flooding by creating gaps in the wallboard and other materials so wicking stops at the gap and you would need to replace only the wallboard or insulation below the gap. The wallboard gap can be disguised by decorative trim such as a chair rail. The gap can be filled with waterproof caulk or a gasket material. Similarly, use a non-wicking waterproof material to separate insulation in the upper wall from that in the lower wall creating the smallest possible gap in the insulation. For VERY shallow flooding you can avoid damage by trimming the bottom so it ends several inches above the floor. Use extra-wide baseboards to cover the gap. (See Diagram).
The anti-wicking technique confines flood damage to the lower part of the wall, even if you use customary building materials. If you have designed the system so paneling, wallboard, and insulation are easily removed and re-installed, you may be able to save them from flood damage.
Use the opportunity created by re-doing the walls to raise the electrical wiring, switches and outlets, ideally moving them to a location above the wicking gaps.
Create Flood-hardy Walls
A flood-hardy wall is one that can stay in place during the flood and require only cosmetic restoration - cleaning and painting, not replacement of materials. A flood-hardy wall (or flood-hardy lower wall section) consists of materials that are flood-damage resistant (see next section). It is designed so flood water enters and drains freely from the wall. Gaps at the top and bottom of the floodable section of the wall must be wide enough to allow flushing (to remove silt and contaminants) and air circulation (to dry the materials before harmful fungi and bacteria take hold).
Interior walls - and the inside face of exterior walls - can be made more flood-resistant with some simple interior finish alternatives:
Note: If you use these techniques on a wall that separates your home interior from the garage, make sure the garage-side of the wall maintains its fire-retardant properties (fire-rated materials, no gapping).
Exterior walls can present more challenges because they typically contain insulation and exterior sheathing. If your exterior wall has solid wood or steel studs, that part is flood-hardy. So the challenge is what to do about the insulation.
If exterior sheathing and or cladding (bricks or siding) is being replaced, there are materials and methods that can be used to improve the water and moisture resistance of the wall even further. Be sure to use references and methods designed for our hot, humid, rainy region, not other parts of the country. LSUAgCenter.com/Home has an excellent collection.
Wet Floodproofing Techniques and Considerations
6-Tips for Reducing Future Flood Damage