HomeMy WebLinkAboutCityofEdinaFloodResilienceFactSheets-03-24-2020_Dry floodproofingFor more information on flood resilience, contact the Engineering Department at 952-826-0371.
1The cost of dry floodproofing varies depending on the building size, depth of required protection, types of material used, and number of openings. Examples of general
cost estimates can be found in FEMA publications: Homeowner’s Guide to Retrofitting: Six Ways to Protect Your House from Flooding and Engineering Principles and Practices
of Retrofitting Floodprone Residential Structures.
What is dry floodproofing?
Dry floodproofing describes a range of strategies to seal the
exterior of a building from flood waters.
Who should use dry floodproofing?
Dry floodproofing is only viable for buildings that are structurally
sound in areas with low-velocity, relatively shallow flooding (below
3 feet). It is most appropriate for slab-on-grade buildings with
concrete or solid masonry walls. Due to risk of structural failure
from excessive flood forces, dry floodproofing is not advised for
homes with basements or homes comprising weaker construction
materials (e.g., wood frame with siding).
Note that dry floodproofing residential structures will not reduce flood insurance
premiums.
What are dry floodproofing
methods?
• Temporary installation of waterproof
membranes: Heavy plastic sheeting or
a waterproof membrane along a wall’s
exterior can be effective in preventing
water from entering the home.
• Use of sealants: Waterproof sealants
can be applied to building walls,
structural joints, and openings for utility
lines. Cement and asphalt-based coatings
are effective, but can drastically change
the appearance of the home and may
be susceptible to puncturing. Clear
coatings (e.g. epoxies or polyurethanes)
can be applied to exterior walls without
changing appearance but tend to be less
effective.
(continued on next page)
Reduces exposure
Reduces vulnerability
COST: VARIES1
Actions for Flood Resilient Homes:
Dry Floodproofing
(Above) “A way to seal an existing brick-faced wall is to add an additional layer of brick
with a seal in between. Please note that weep holes (drainage) and wick drains are moved
up to prevent moisture from getting inside the walls.” Images and descriptions provided by
FEMA P-312, Homeowner’s Guide to Retrofitting 3rd Edition (2014)
(Left) Example of exterior application of asphalt
membrane (courtesy of https://staydrywaterproofing.com/)
(Right) An interior application of a fiber-reinforced polymer
wrap, image provided by FEMA P-312, Homeowner’s Guide
to Retrofitting 3rd Edition (2014)
Before flood action During flood action After flood action
Flood level
Existing walls
Brick ties
Fully grouted
Existing floor
New foundation extension tied to
existing foundation with steel dowels
Existing
foundation
New foundation
(added to support
new brick veneer)
Ground
New drain or
relocated drain,
or sump pump in
crushed stone
New masonry veneer
New masonry rowlock
Grout
Existing masonry veneer
For more information on flood resilience, contact the Engineering Department at 952-826-0371.
Other considerations
• The Federal Emergency Management Agency recommends that dry floodproofing should be designed by licensed professionals.
Failure to anticipate hydrostatic forces (force due to the pressure of a fluid at rest) may result in extensive damage.
• Placement of flood shields or waterproof membranes is not feasible during flash floods or when warning times are short.
• Ongoing maintenance is required.
• Flood shields and sealants may not be aesthetically pleasing.
• Dry floodproofing does not mitigate the potential impact of high-velocity flood flow, wave action, erosion, or debris.
Actions for Flood Resilient Homes:
Dry Floodproofing
• Addressing closures: Openings in the walls need
to be either temporarily or permanently sealed
shut. For example, low window openings at ground
level can either have a pre-sized closure fitted over
their surface or a low wall constructed around the
opening. Similarly, all or part of a low window could
be replaced with brick or glass block.
• Using flood shields: Temporary watertight
shields can be placed over windows or doors in
anticipation of flooding. Most residential shields can
be stored in the home and installed when needed
by bolting them into place or securing them in
permanently installed brackets or tracks.
• Addressing interior drainage: A good interior
drainage system to collect leaking water (e.g., a
sump pump with an emergency power source) is
an important component of a dry floodproofing
system. Sanitary backflow prevention is also
recommended.
(Above) Metal shields installed with bolts or permanently installed
tracks; image courtesy of www.psfloodbarriers.com/wp-content/uploads/
sites/4/2016/09/Flood-Plank-21.jpg
(Left) Low window raised and original opening filled with brick; image
provided by FEMA P-312, Homeowner’s Guide to Retrofitting 3rd Edition
(2014)
What are dry floodproofing methods? (continued)