State University Extension
Home Maintenance And Repair - 01500014
Drying Walls After A Flood
Walls must dry from the inside out. The interior framing of walls
should be allowed to dry thoroughly. Sometimes this process takes weeks
or even months. To release water and mud from walls remove top and
bottom strips of siding on the outside of the building. Drill several
holes in walls near the inside floor line.
The total drying time will depend partially on the amount of dry air
that can circulate through the studding (called "chimney action"). To
provide for maximum chimney action, first consider the construction of
Fire Stops or Cross Bracing
These are horizontal or diagonal braces between the vertical supports
Cross bracing will prevent chimney action between the studding.
However, cross bracing is not usually found in modern construction,
except in two-story houses where is has been specified. To allow free
air movement, remove interior or exterior wall covering wherever cross
braces are located. To check for cross bracing or fire stops, extend a
stiff wire into the wall cavity.
Any types of insulation will be ruined if water- soaked. You will
probably have to replace flood-soaked insulation.
1. Loose fill (such as vermiculite) will settle to the bottom of walls.
As it dries it can be removed. If not removed, loose fill insulation
will create odors and eventually cause decay of the studding.
2. Rock wool batting insulation will also bunch and settle. If it is
absorbent it will create odors and could eventually cause studding
3. Fiberglass batting will also bunch, but will not develop odors. Its
insulating value will be greatly reduced.
4. Reflective surfaces (such as aluminum foil) will probably lose their
reflective ability thus decreasing their insulating effectiveness. The
material itself should be undamaged.
Wall Coverings and Finishes
1. Plaster will take weeks or even months to dry but may not be ruined
by water. Old plaster, however, may disintegrate after being wet for a
2. Dry wall (plaster board) will warp and disintegrate in water.
Warping above the water level can also be expected. Drywall that has
been submerged must be replaced.
3. Laminated paneling (plywood, masonite) will separate and warp above
and below the water level. The extent of damage will depend on how long
the paneling was submerged, and how quickly moisture is removed from
the studding. Slow drying decreases the possibility of delamination.
1. Masonry will dry slowly but will be undamaged except for possible
cracking or settling. Open inside walls to prevent mildew and decay of
2. Lapped siding (wood, asbestos, aluminum). Remove strips or sections
to dry insulation and studding. The type of sheathing will determine
drying rate. To prevent oxidation, make sure backing of aluminum siding
Sheathing (material between studding and finish siding)
1. Wooden boards will dry slowly and some will warp. If possible,
renail warped areas before they dry. Replace those that are too badly
warped to salvage.
2. Sheathing board is usually absorbent and will be difficult to dry.
Some will disintegrate or separate and must be replaced.
3. Plywood will probably separate in places and must be replaced.
Marine plywood will not warp or separate, but is generally considered
too expensive to use in residential construction unless the building is
subjected to frequent flooding.
This article was written by Anne Field, Extension Specialist, Emeritus,
with reference from the USDA Disaster Handbook.
to main page
This information is for
educational purposes only. References to commercial products or trade
names does not imply endorsement by MSU Extension or bias against those
not mentioned. This information becomes public property upon
publication and may be printed verbatim with credit to MSU Extension.
Reprinting cannot be used to endorse or advertise a commercial product
MSU is an
employer. Michigan State University Extension programs and materials
are open to all without regard to race, color, national origin, gender,
gender identity, religion, age, height, weight, disability, political
beliefs, sexual orientation, marital status, family status or veteran
status. Issued in furtherance of MSU Extension work, acts of May 8 and
June 30, 1914, in cooperation with the U.S. Department of Agriculture.
Thomas G. Coon, Director, MSU Extension, East Lansing,MI 48824. This
information is for educational purposes only. Reference to commercial
products or trade names does not imply endorsement by MSU Extension or
bias against those not mentioned.
information.was reviewed as
of June 2008. For more information about the contents please
for webpage problems