HomeMy WebLinkAboutCityofEdinaFloodResilienceFactSheets-03-24-2020_wet floodproofingFor more information on flood resilience, contact the Engineering Department at 952-826-0371.
1Costs of wet floodproofing vary with the methods adopted. Major costs are associated with rearrangement of utility systems, installation
of flood vents, and replacement of materials that are not resistant to floods. Note that wet floodproofing will not reduce flood
insurance premium rates on residential structures.
What is wet floodproofing?
Wet floodproofing refers to a range of
strategies used to prevent or provide
resistance to flood damage—while allowing
water into the uninhabited portion of
a building (e.g., unfinished basement,
crawlspace, garage). Allowing floodwater
to enter the enclosed areas of a home
equalizes pressure, which can prevent
structural damage. Successful wetproofing
involves (1) ensuring that floodwaters inside
the home rise and fall at the same rate as
floodwaters outside the home, (2) reducing
damage through the use of flood-resistant
materials, (3) protecting service equipment
inside and outside of the home, and (4)
relocating any high-value items stored
below the designed flood elevation (DFE).
• Elevate appliances and utilities or install
barriers: Items that should be elevated or protected
with a barrier include your furnace and air-conditioning
unit, outside air-conditioner compressor, washer and
dryer, water heater, freezer, and electrical outlets and
switches. You can also relocate these to a place in your
home that is higher than the DFE (e.g., an attic), or build
a small addition that would serve as a utility room and
as storage for valuable furnishings during a flood.
• Use flood-resistant materials: The Federal
Emergency Management Agency (FEMA) publishes
flood-resistant classifications for flooring, wall, and
ceiling materials, as well as the adhesives used to install
them (Technical Bulletin 2-08). Carpeting, paneling, and
gypsum wallboard can all be replaced with materials
that would require cleaning rather than replacement.
A table on the following page lists materials that are
acceptable in wet floodproofing home projects.
(continued on next page)
Actions for Flood Resilient Homes:
Wet Floodproofing
Reduces exposure
Reduces vulnerability
COST: VARIES1
Before flood action During flood action After flood action
Wet floodproofing techniques for a house. Image from FEMA P-259 (Figure -10)
https://www.restoration1greaterminneapolis.com/how-to-deal-with-a-flooded-basement
What are wet floodproofing methods?
An advantage of wet floodproofing is that it is flexible; it can be done in stages—many of them relatively inexpensively.
A good time to employ wet floodproofing strategies is when you remodel your home. The following are some wet
floodproofing methods:
Base flood elevation
Who should use wet floodproofing?
If you are at risk of flooding and cannot elevate your home or build reliable
flood barriers, wet floodproofing of non-living spaces is an option. It is
most suitable for shallow flooding that inundates uninhabited space. It is not
practical for most slab-on-grade structures that have the living space at or
near ground level. Also, it is not a reasonable approach if the duration of a
flood is expected to be more than one day.
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
Other considerations
• Ongoing maintenance is required to minimize flood
risks.
• Pumping water from a basement too soon after a
flood may lead to structural damage.
• Work on electrical systems, gas systems, or air-
conditioning compressors requires a licensed
contractor, and permits may be required.
Actions for Flood Resilient Homes:
Wet Floodproofing
What are wet floodproofing methods? (continued)
Materials that are acceptable in wet floodproofing home projects:
Material Type Acceptable Unacceptable
Structural Flooring Materials • Concrete
• Naturally decay-resistant lumber
• Pressure-treated plywood
• Oriented strand board (OSB)
Finish Flooring Materials • Clay tile
• Ceramic or porcelain tile
• Terrazzo tile
• Vinyl tile or sheets
• Engineered wood or laminate flooring
• Carpeting
• Wood flooring
Structural Wall and Ceiling Materials • Brick face, concrete, or concrete block
• Cement board/fiber-cement board
• Pressure-treated plywood
• Solid, standard structural lumber (2x4)
• Non-paper-faced gypsum board
• Fiberglass insulation
• Paper-faced gypsum board
• OSB
Finish Wall and Ceiling Materials • Glass blocks
• Metal cabinets or doors
• Latex paint
• Wood cabinets and doors
• Non-latex paint
• Particleboard cabinets and doors
• Wallpaper
FEMA P-312, Homeowner’s Guide to Retrofitting 3rd Edition (2014)
• Sewage backflow prevention is important; a backflow valve
should be installed.
• Because wet floodproofing allows your home to flood,
extensive cleanup may be necessary to remove potential
chemical and biological contamination and prevent mold
growth and decay.
• Install flood vents: Flood vents (permanent openings)
allow water into the structure, equalizing interior and
exterior pressures to avoid structural damage.
(Above) “Wall openings must allow floodwaters not only to enter the home, but
also to rise and fall at the same rate as floodwaters outside the home.” Images
provided by FEMA P-312, Homeowner’s Guide to Retrofitting 3rd Edition (2014).
(Left) Base flood elevation and location of flood vents. Images provided by FEMA
Technical Bulletin 2, 2008, Openings in Foundation Walls and Walls of
Enclosures.
Base flood elevation