Reconstruction of houses in
flood prone area
Follow recommended for removal and replacement of existing housing envelope
materials.
Siding
• Fiber cement and vinyl sidings better withstand flood conditions than
hardboard lap siding and plywood siding.
• Replacing trim and corner boards with plastic or wood/plastic composite is
likely more cost-effective than restoring (thorough drying, renailing, crack
filling, and repainting) sawn wood trim.
Sheathing
• Plywood sheathing with flood-damage-resistant lap siding is a good
combination. Plywood sheathing covered with plywood siding does not dry well and
is not recommended.
• Water-resistant, fiber-reinforced gypsum sheathing (e.g., Fiberock WR
Sheathing by USG) is a good sheathing material.
• Fiberglass and other moisture-retaining insulation in the exterior cavity is
not recommended
Wood Framing
• Wood is a good flood damage-resistant framing material as long as the wall or
floor system will allow it to dry. Fiberglass and other moisture-retaining
insulation in the exterior cavity or subfloor is not recommended.
Insulation
• Spray polyurethane foam insulation is a much better for flood
damage-resistance than fiberglass batt insulation.
Gypsum Wallboard (drywall)
• Water-resistant, fiber-reinforced gypsum exterior sheathing can generally be
restored to preflood condition with only cosmetic restoration. Though it
supports mold growth on the exposed surface, it can be cleaned, sanitized and
restored.
• Gypsum board that is able to dry completely within an appropriate time can
generally be restored to preflood condition with only cosmetic restoration.
Although it supports mold growth on the exposed surface, it can be cleaned,
sanitized and restored.
• Gypsum wallboard is available with a non-paper skin. The paper in wallboard is
a source of food for mold and eliminating the food reduces the potential for
mold growth
• Gypsum board with fiberglass batt insulation on exterior walls generally dries
too slowly to maintain its integrity.
Wall Finishes
• Oil-based flat enamel generally performs better than water-based latex;
flaking and blistering very little and much easier to restore than other paints.
• Standard drywall compound and paper joint tape performs very poorly under
flood conditions. Quick setting joint compound and fiberglass tape are generally
a great improvement. When used with the water-resistant gypsum sheathing and
oil-based paint, these materials are expected to require minimal repair.
• Vinyl wall covering will blister, peel, and debond after flooding. It damages
the surface of the gypsum board and may inhibit drying of the substrate or wall
system.
• Ceramic tile generally performs well under flood conditions with no long-term
deterioration.
Exterior Doors
• Exterior wood paneled doors, exterior prehung metal-clad doors in wooden
frames; fiberglass and foam-filled metal doors can generally be restored to
preflood conditions with minimal effort.
• Do not fill the joints between the outside of the door frame and the rough
opening with compressed fiberglass insulation because it may retain excessive
moisture. Filling with low expansion foam is the preferred option.
Interior Doors
• Considering the relatively low cost of replacement, it is generally cost
effective to replace all types of interior doors.
Windows
• Vinyl and aluminum window frames are generally able to be restored to preflood
conditions with a minimal cleaning effort.
• Do not fill the joints between the outside of the window frame and the rough
opening with compressed fiberglass insulation because it may retain excessive
moisture. Filling with low expansion foam is the preferred option.
Floors
• Sealed concrete floor slab in all slab-on-grade modules generally remain
undamaged during and after flooding.
• All carpeting (including water resistant) and padding holds or traps water and
should be removed, dried and cleaned as part of the flood recovery process.
• Wood flooring holds or traps water above the slab and slows the overall drying
process. If cost-effective, wood flooring should be removed, washed and stacked
during the drying process.
• Ceramic and quarry tiles absorb little water and do not significantly slow the
drying process.
• Wood and plywood subflooring and framing retains moisture and could be subject
to long-term moisture problems when un
faced fiberglass batt insulation is installed underneath the subflooring. With
no floor insulation, the subflooring generally dries well.
• Drying of the subfloor is predominantly through its bottom side.
• Both glued-in-place and floating vinyl flooring on padding traps water, so
they should be removed during the drying process.
If the flooring can be removed without damaging it, vinyl flooring can be reused
if it is cost-effective to do so.
Foundation Vents and Crawl Spaces
• Conventional foundation vents and operable flood vents both perform well.
• Conventional vents may become blocked by debris during flooding, which could
cause damage to the structure.
• Block open operable vents throughout the drying period to permit air to
circulate through the crawl space.
• Flood-damaged homes undergoing restoration in wet climates may require
regrading of the site to promote drying in the crawl space.
• The crawl space area must be effectively sealed at all penetrations in the
flooring to cut off potential pathways for the excess moisture and mold to enter
the interior of the home. Ductwork, especially return air, within the crawl
space should also be sealed after it has been cleaned, sanitized, disinfected,
and repaired as necessary.
Install insulation and wall materials to the full height of the walls subjected
to flooding. Uncertainty regarding future flood levels and the wicking of
floodwater through materials make the combining of conventional materials and
flood damage resistant ones imprudent.
When selecting envelope materials and finishes, and caulking/sealing methods it
is wise to assume that floodwater will permeate the system and that there will
be hidden pockets of moisture that will require a "means of escape". This escape
could be through permeable materials such as gypsum board or through cracks such
as through the joints in vinyl siding. Don't block this means of drying with low
permanence paints and wall coverings on walls or with caulking joints.