Protecting Your Property from Flooding: Exterior Walls
Are You At Risk?
If you aren't sure whether your house is at risk from
flooding, check with your local floodplain manager, building
official, city engineer, or planning and zoning administrator.
They can tell you whether you are in a flood hazard area.
Also, they usually can tell you how to protect yourself and
your house and property from flooding.
What You Can Do
Flood protection can involve a variety of changes to your
house and property -- changes that can vary in complexity and
cost. You may be able to make some types of changes yourself.
But complicated or large-scale changes and those that affect
the structure of your house or its electrical wiring and
plumbing should be carried out only by a professional
contractor licensed to work in your state, county, or city.
One example of flood protection is adding a waterproof veneer
to the exterior walls of your house. This is something that
only a licensed contractor should do.
Add Waterproof Veneer to Exterior Walls
in areas where flood waters are less than 2 feet deep, a house
can be severely damaged if water reaches the interior. The
damage to walls and floors can be expensive to repair, and the
house may be uninhabitable while repairs are underway.
One way to protect a house 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.
As shown in the figure, 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. Also, because the
wall will be exposed to flood water, changes are made to the
interior walls as well so that they will 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.
Keep these points in mind when you have a waterproof veneer
added to the exterior walls of your house:
- Adding a waterproof veneer is appropriate in areas where
the flood depth is less than 2 feet. When flood depths
exceed 2 feet, the pressure on waterproofed walls
increases greatly, usually beyond the strength of the
walls. If greater flood depths are expected, consult with
a licensed civil or structural engineer before using this
- Changes to the foundation of your house must be done by
a licensed contractor, who will en-sure that the work is
done correctly and according to all applicable codes. This
is important for your safety.
- If your house is being remodeled or repaired, consider
having the veneer added as part of the remodeling or
repair work. It will probably be cheaper to combine these
projects than to carry them out separately.
- If your house has brick walls, you can still use this
method. The new brick veneer and water-proof membrane are
added over the existing brick.
- If your house is flooded by groundwater entering through
the floor, this method will not be effective.
If you have a contractor add a waterproof brick veneer to
your house, you can expect to pay about $10 per square foot of
exterior wall. For example, a 3-foot-high brick veneer on a
house measuring 60 feet by 30 feet would cover about 540
square feet and would cost about $5,400. This figure does not
include the cost of sealing doors and other openings or
extending the foundation.
Other Sources of Information
- Protecting Your Home from Flooding, FEMA, 1994
- Repairing Your Flooded Home, FEMA-234, 1992
- Flood Emergency and Residential Repair Handbook, FIA-13,
- Retrofitting Flood-Prone Residential Structures,
- To obtain copies of these and other FEMA documents, call
FEMA Publications at 1-800-480-2520. Information is also
available on the FEMA