Patricia Skinner, Baker, Eugene, Reichel, Claudette H.
Making a Building Watertight
Sealing a building so water will not enter is called dry floodproofing. The interior spaces, equipment and contents of the building stay dry.
Dry floodproofing, which is called simply "floodproofing" in FEMA publications, is an alternative to elevation for non-residential buildings only - not for homes. New and substantially damaged or improved homes must be elevated. Disaster mitigation funds are not typically used for dry floodproofing a home, though some exceptions have been made on an experimental basis.
Permanent dry floodproofing of an existing building can be done by applying a long-lasting, waterproof sealant coating or membrane over siding (if relatively flat) or brick veneer, or, with greater effort, on the sheathing behind the siding or veneer.
Penetrations in the walls must be sealed. These would include passages for plumbing and for central air-conditioning condensate drains, openings for telephone and electrical lines, and any other channels through the walls. In addition, all doors and windows - and the door frames and window frames - need to be made watertight or be covered with watertight panels during flood events. See also "Using Panels as Closures for Flood Protection" and a description of temporary dry floodproofing by wrapping with plastic: "Flood Wraps and Shields".
This technique has significant drawbacks for wood-frame construction in hot, humid climates, related to moisture control. For these structures it should be a last resort. It should always be done by, or with guidance by, a qualified professional.
The diagram (click to enlarge) shows methods for sealing two types of exterior walls -- Please refer to the diagram above. The critical components of the wall are numbered: