Floods are the most regular type of natural catastrophe. These occurrences are the result of rising water from storm surges, heavy rainfall, and fast snowmelt. These rising waters offer little to no warning and are devastating to everyone in their path.
While we are unable to stop these natural occurrences, we can take steps to mitigate flood damages. Consumers living in high-risk areas should consider taking steps to floodproof their dwellings.
There are tactics you can take to prevent your home from becoming substantially flood-damaged. These nonstructural and structural changes, also known as floodproofing, can help save millions. FEMA reports a savings of $5 for every $1 invested in flood mitigation.
You can install wet floodproofing or dry floodproofing.
What is Wet Floodproofing?
Wet floodproofing is a construction method that allows floodwater to enter enclosed areas of a home. The ultimate example of wet floodproofing is a home on stilts. But additional measures exist other than stilts to wet floodproof your house (we will cover them further below).
The premise of wet floodproofing is if floodwaters enter a home's enclosed areas and quickly reach the same height as the surrounding outside floodwaters, the impact of hydrostatic pressure, including buoyancy, is significantly reduced.
Consequently, wet floodproofing may substantially lessen the loads imposed on a house and structural damages they cause during a flood.
When adding wet floodproofing features to your home, it benefits certain areas the most, such as damages to:
- Enclosures below elevated buildings
- Below-grade basements
- Walkout-on-grade basements
- Attached garages
However, it is not practical for everyday living spaces.
Effective wet floodproofing involves the following:
- Ensures floodwaters enter and exit the house
- Relocates and protects items stored below the Flood Protection Elevation (FPE)
- Ensures floodwaters inside the house rise and fall at the same pace as floodwaters outside
- Protects the areas below the baseline flood level from floodwater damages
- Protects equipment and appliances inside and outside the house
Wet Floodproofing vs. Dry Floodproofing
The two most common floodproofing techniques are dry floodproofing and wet floodproofing. Both options serve to reduce flood losses and losses of human life.
Dry floodproofing is when you make changes to prevent floodwaters from entering your home. These changes include:
- Installing watertight protectors for doors and windows
- Reinforcement of Walls
- The use of sealants to prevent floodwaters from seeping in
These flood protection techniques are not recommended for all structures. FEMA prohibits dry floodproofing to dwellings located in a special flood hazard area.
Residential wet floodproofing is the opposite of dry floodproofing. Instead of keeping rising water out, it allows the water to flow in and out, usually by raising the house above the flood baseline. This technique reduces damages caused by the water and its hydrostatic pressure.
Taking steps to reduce damages caused by rising water benefits the entire community. It reduces business interruption in commercial buildings and saves millions in taxpayer dollars.
FEMA Wet Floodproofing
The steps taken to wet floodproof vary depending upon the specifics of a structure. The following are the most common wet floodproofing practices.
The installation of wall openings is the most critical step to wet floodproofing a home. These openings should be in the garage, foundation, and basement walls. Placing them below expected flood levels ensures equalization of hydrostatic pressures.
Elevation or Relocation of Appliances
Rising waters can damage or destroy a dwelling's appliances, water heaters, and electrical systems. Contractors elevate threatened systems to help safeguard against a loss. Elevated structures made with pressure-treated wood ensure they can withstand the flood's forces.
Flood-Resistant Construction Materials
Many construction materials are available on the market that can mitigate flood damages. You no longer must sacrifice beauty to floodproof your home.
Examples of materials that meet FEMA wet floodproofing construction standards include:
- Waterproof Mortar
- Clay Tile
- Chemical-set Adhesives Used with Solid Vinyl Flooring
- Rigid, Closed-cell Foam Insulation
- Pressure-Treated Wood
- Wood Resistant to Decay
- Stained Concrete
Floodproofed spaces should be void of all materials that trap moisture. Failure to comply could reduce the effectiveness of your new materials.
Install Drainable Walls
The concept behind wet floodproofing is that water should be able to flow in and out of the lower part of your home. To ensure proper draining, you will need to install removable baseboards and wainscoting.
Materials such as gypsum wallboard reduce wicking and prevent wetness.
Those steps ensure easy cleanup and drying after a flood.
FEMA Wet Floodproofing Requirements
FEMA only allows wet floodproofing in specific situations, in accordance with the National Flood Insurance Program standards.
Situations where wet floodproofing is appropriate include:
- Historical homes when elevating the structure is not an option
- Homes with attached garages or storage sheds
- Homes above Base Flood Elevation (BFE) that are prone to flooding
- Pre-FIRM homes that are below the BFE
FEMA has published specific standards for wet floodproofing a structure. You can find those requirements in the previous section.
FEMA Planning Considerations
There are essential factors to consider when determining if wet floodproofing is appropriate. These considerations are set forth in FEMA's Technical Bulletin 7-93.
- Warning Time. Residents must have enough warning time before rising waters occur.
- Safe Access. Residents must be able to access and escape the site without injury.
- Duration of Flooding. A structure prone to prolonged flooding is subject to structural deterioration.
- Frequency of Flooding. Homes prone to flooding may not profit from wet floodproofing.
- Water Temperature. Ice is often a factor in cold-weather climates. Chunks of ice can hinder the flow of water in and out.
- Flash Floods. Areas prone to flash floods do not meet the standards for dry or wet floodproofing. Relocation or elevation are appropriate alternatives in these situations.
FEMA Guidelines for Flood Cleanup
FEMA has issued guidelines for cleaning up after a flood. Safety is the number one priority. Proper access and cleaning help protect against contaminant exposure.
You should avoid using electrical receptacles in flooded areas. A certified electrician should check the system before using it. Deactivate your power system until that time.
In situations where mold growth is visible, protect yourself with safety gear, including a full-face respirator, as well as hand and clothing protection. If a full-face respirator is not available, an N-95 mask and goggles are appropriate.
If your home has asbestos or lead paint, have a professional inspect the site. State and federal regulations for cleanup are applicable.
FEMA's published cleanup standards include:
- Installation of Plastic Barriers. These barriers help prevent the spread of mold to unaffected areas.
- Cleaning and Sanitizing. All products used must meet EPA standards to protect you from harmful contaminants from the sewer lines.
- Cleaner Application. The most efficient cleaning process involves first applying a foam cleanser. Affected areas must then be pressure washed. Cleaning the crawlspace is critical for proper cleanup.
- Drying. Once the home is clean, the drying process can begin. The moisture content will help determine what drying equipment is appropriate.
To ensure proper cleanup of your home after a flood, consider hiring a professional. A professional ensures the safety of both your family and your home.
FEMA Wet Floodproofing Certificate
A floodproofing certification will be necessary if you floodproof your home. A registered architect or engineer must complete the inspection.
Using FEMA's one-page wet floodproofing certification form will ensure you meet all floodplain management requirements. This certification is also used for insurance rating purposes.
Advantages and Disadvantages of Wet Floodproofing
Before flood waterproofing your home, you will need to consider the pros and cons. The advantages to wet floodproofing include:
- Financial Costs. These techniques cost less than other available options.
- Mitigates Structural Damage. Even minor changes help reduce the risk of damage.
- Hydrostatic Pressure. The equalized hydrostatic pressure lowers the pressure on your home's floors and walls.
- Flood Insurance Rate. It impacts your ability to get flood insurance and lowers its rates.
The disadvantages to wet floodproofing include:
- Evacuation. You cannot occupy your home during a flood. You will also need to move items located on the lowest floor.
- Cleanup. Because wet floodproofing allows water in, the lower level space will be wet after a flood. Extensive cleanup is sometimes necessary.
- Limited Use. You may not have full use of the area.
Your home's situation is unique to everyone else's. Speak with a professional and weigh all the pros and cons before investing.
Wet Floodproofing Cost
The cost for residential wet floodproofing averages between $6,000 - $8,000. Wet floodproofing costs are lower than other techniques. The costs vary depending upon the methods employed and materials used.
Partial Wet Floodproofing Technique
Partial wet floodproofing focuses on the structure's most vulnerable areas.
Flood Vents in Wet Floodproofing
Flood vents are permanent openings in foundation walls. These vents allow floodwaters to exit the structure, reducing pressure on the building's structure and allowing for faster drying.
Flood vents must measure one square inch per square foot of enclosed floor space.
Flood-resistant walls, also known as waterproof veneers, mitigate floodwater damage. Veneers are most appropriate in areas where the flood level is two feet or fewer.
Rising water can result in loss of life and significant damage to personal property. Take the above steps to ensure your home can withstand the pressures of floodwaters. In turn, this helps minimize damages.
Hope that helps!
At your service,