Floods: Floodproofing - Wet

Material provided by Federal Alliance for Safe Homes http://www.flash.org/

This procedure makes uninhabited parts of your home resistant to flood damage when water is allowed to enter during flooding. An example of wet floodproofing is to install flood vents, creating permanent openings in the foundation walls. This retrofit requires at least two vents on different walls. The size of the vents must be 1 square inch per square feet of enclosed floor area. For example, a 1,000 square foot house would require 7 square feet of flood vents. 

Another way to protect your property from shallow flooding is to add a waterproof veneer to the exterior walls and seal all openings, including doors, to prevent the entry of water. The veneer can consist of a layer of brick backed by a waterproof membrane. Before the veneer is applied, the siding is removed and replaced with exterior grade plywood sheathing. If necessary, the existing foundation footing is extended to support the brick. Because the wall may be exposed to flood water, changes are also made to the interior walls to resist moisture damage. In the area below the flood level, standard batt insulation is replaced with washable closed-cell foam insulation, and any wood blocking added inside the wall cavity is made of exterior grade lumber.

Benefits of Using This Mitigation Strategy


Keep these points in mind if you plan to have a waterproof veneer added to the exterior walls:

Estimated Costs

If you have a contractor add a waterproof brick veneer, you can expect to pay about $10 per square foot of exterior wall. For example, a 3-foot high brick veneer on a structure measuring 60 feet by 30 feet would cover about 540 square feet and would cost approximately $5,400. This figure does not include the cost of sealing doors and other openings or extending the foundation.

Technical Information Provided by FEMA