Flood Retrofits
Learn how to retrofit your home or business to protect it against flooding.
Damage from just one inch of water in an average-size home can cost roughly $25,000 in clean-up and repairs. Retrofitting your home or business to be more flood resilient could save you money in the long run and may even lower your flood insurance premiums. |
There are many ways to protect your home or business against flooding—from lower-cost, simple changes to bigger projects that require professional help.
Renters
Many flood prevention and cleanup resources are directed towards property owners, as it often involves making changes to the property. However, about 65% of Boston households are renters. The best short-term approach, especially for renters, is to simply raise valuables as high as practicable within your home. The Mayor’s Office of New Urban Mechanics provides additional flood guidance specifically for renters that includes protective measures, safety tips, and resources.
Property Owners
For homeowners and business owners considering retrofits, consult with licensed and qualified professionals and get at least three quotes to compare prices. All information, including installation details, cost estimates, and useful life expectations, is provided for informational purposes only and may vary based on property conditions, labor rates, materials, and other factors. Links to third-party resources are provided for convenience only and do not constitute or imply endorsement.
Start by visiting the Knowing Your Flood Risk page to view your property's potential flood risk and find your Base Flood Elevation (BFE). The BFE is the expected depth of flooding that has a 1% chance of occurring in any given year. To determine your BFE, use the FEMA Flood Map Service Center website to locate your property and find the "EL" labeled number (e.g., EL 10 is an expected flood depth of 10 feet).
Retrofits cannot impact neighboring properties or protected wetland resource areas. View the Boston Conservation Commission’s guide to locate wetland resource areas. Retrofits that could impact these areas require review and permitting. Before taking action, please contact the Boston Conservation Commission at cc@boston.gov to learn about what additional permitting steps you may need to complete.
For more information, technical guidance, and retrofit case studies for various building types, see the Coastal Flood Resilience Design Guidelines.
If you have questions about permitting requirements for flood retrofits, visit Inspectional Services Permitting in the Flood Hazard District page or email ISDFlood@boston.gov.
-
Still have questions? Contact:
Emergency Management
-
85 Bragdon Street
Boston, MA 02119
Flood Retrofit Options
options
Purchase a rain barrel to capture rainwater runoff from your roof and help conserve water, reduce your flood risk, and lower your water bill. One inch of rain on a 1,000 square foot roof yields 623 gallons of water. Just 1/4 inch of rainfall on a typical roof will fill a rain barrel and can be used to water a 200 square foot garden.
Installation: Place the barrel near your roof’s downspout, attaching one end of a diverter to the downspout and the other end to the barrel, and collect water for storage. Attach a spigot or garden hose to the barrel and use the water for gardening or washing your car. Rain barrels come with a mesh screen to prevent debris from getting into the barrel, which needs to be cleaned regularly. The barrel should be cleaned at least once per year using vinegar, bleach, or dish soap to prevent algae and bacterial growth. Drain and store your barrel during the winter months to prevent water from freezing and cracking the barrel. Visit the Office of Green Infrastructure’s Community Rain Barrel Program page for more information on purchasing and installing a rain barrel.
Cost: A 55-gallon rain barrel is $80-$89 through the City’s Community Rain Barrel Program. Market price is $199-$160.
Useful life: With annual maintenance, 10-30 years
Seal cracks in foundation walls. Basements, garden-level apartments, and any areas below street level are vulnerable to flooding. Seal minor foundation cracks with a waterproof filler. Cracks that are wider than 1/4 inch, horizontal, or stair-step shaped need an expert assessment, as they may be signs of structural problems.
Installation: Epoxy works well for small, hairline cracks, while polyurethane is better for larger cracks up to 1/4 inch. Be sure to clean the surface using a wire brush and vacuum loose debris before applying the filler.
Cost: Materials for small crack repairs cost $10-$100. Costs vary for a professional to fix larger cracks and depend on the underlying cause.
Useful life: 5-10 years for smaller cracks
Use flood-resistant materials. Replace carpet with tiles and use flood-resistant insulation and sheetrock. Non-paper-faced gypsum board and terrazzo tile flooring are good options. You can also install floodproof cabinets or replace wooden items with metal ones. Costs vary depending on the materials used and the size of the area.
Install a backwater valve that opens to allow wastewater to flow out of your home into the city sewer system and closes to prevent sewage from traveling backward from the sewer into your basement during heavy rain or flooding. When the valve is closed during heavy rain, you should avoid using sinks, toilets, or showers so water doesn’t back up into your home. Valves should be checked and cleaned at least annually. Sewage backups can cost $2,000–$10,000 for cleanup and repairs. Check to see if your insurance covers sewage backup.
Installation: Takes 2-8 hours. Hire a licensed plumber. Be sure to ask if they have installed backwater valves before, and what type of valve they recommend for your home.
Cost: $600-$5,000
Useful life: 5-15 years
Install a sump pump to remove water from your basement or crawlspace. Water is directed into a pit or basin. When the water reaches a certain level, a float activates the pump, which pushes water away from your foundation through a discharge pipe into your yard. Once the water is pumped out, the float drops and the pump shuts off. A battery-powered backup will allow the pump to work during power outages.
Installation: A sump pump and basin should be installed by a licensed professional. A plumbing permit is required, and an electrical permit may be needed if installation requires new electrical circuits or upgrades. Sump pumps may not discharge to the city’s sewer system. A dewatering discharge permit is needed from the Boston Water and Sewer Commission to discharge water into the city’s stormwater drains. Be sure the basin is properly sealed to prevent radon gas from entering your home. Test radon levels annually to ensure they are below the EPA action level of 4 pCi/L.
Cost: Approximately $3,500 (Submersible pumps are quieter and more efficient than pedestal pumps, but are more expensive.)
Useful life: 7-10 years
Anchor your fuel tank to prevent it from floating or tipping in floodwaters and causing spills or fires.
Installation: Takes 2-5 hours or longer if a new concrete slab is needed. A licensed professional is needed to anchor your fuel tank to a properly anchored, reinforced concrete slab using galvanized, non-corrosive metal structural supports and fasteners. Rubber or vinyl shields should be placed between the metal straps and the tank to prevent corrosion. Vent pipes should be extended above the BFE.
Cost: $300-$500
Useful life: 20-30 years with maintenance every 5-10 years.
Install flood vents, which are small openings near the bottom of your home that allow flood waters to flow through safely and reduce pressure on your walls that can cause structural damage. Mechanical equipment for heating, ventilation, and air conditioning must be raised above the flood plain before installing flood vents.
Installation: Requires a licensed professional and can be installed in a few days. FEMA and MA building codes (780 CMR) require at least two vents on different walls with 1 square inch of opening per square foot of enclosed area. Openings should be no more than 12 inches from the ground. A short-form building permit is required and may be requested through Boston Inspectional Services’ permitting portal. Additional approvals from the Boston Conservation Commission may be needed if your property is near a designated wetland.
Cost: Approximately $3,000, including $150-$200 per vent, $150-$200 for installation, and a building permit of $20 for the primary fee and $10 per $1,000 of the estimated cost of work.
Useful life: 15 - 20 years with annual maintenance
Elevate or floodproof your heating, cooling, hot water, and electrical systems. Floodwaters can damage your systems, costing thousands to repair, and leaving you without power, heat, or hot water. There are a few ways to protect your systems and even lower your insurance premium by $100 - $200 per year.
Option 1: Use a masonry base to raise systems at least 12 inches above the BFE. Contact a licensed surveyor to determine your BFE and to get an elevation certificate, which compares the height of your home’s lowest floor with the BFE. The certificate is needed to lower your flood insurance premium.
- Installation: Requires a licensed professional. Use reinforced concrete and properly anchor the slab to withstand water pressure. Secure the furnace, water heater, HVAC unit, or electrical panels to the masonry base using galvanized anchor bolts or stainless steel straps to prevent flotation during a flood. Apply a waterproof coat to the slab to prevent water seepage.
- Cost: Typically $500 - $2,500 for materials and labor
- Useful life: 100+ years with mortar joint maintenance every 25-50 years. Salt water exposure, freezing, and thawing reduce the lifespan.
Option 2: Build a flood wall around systems higher than the BFE, typically 1-5 ft.
- Installation: Requires a licensed professional. Flood walls are properly anchored, reinforced concrete able to withstand water pressure. Leave 2-3 feet around the system for maintenance access and air flow. Use hydraulic cement or masonry caulk to seal any gaps in the wall and between the wall and the house foundation. Install a removable gate for servicing the unit.
- Cost: $2,500 - $6,000 for a 3-foot-high, 35-foot-long barrier.
- Useful life: 30-50 years with sealant maintenance every 5-10 years.
Option 3: Move systems from the basement to an upper floor or the attic.
- Installation: Takes a few days to a few weeks, depending on what needs to be moved. Requires a licensed professional for structural, electrical, plumbing, gas line, and ductwork modifications. If adding or changing walls to accommodate the modifications, a building permit will be necessary.
- Cost to move systems:
- Furnace $3,000 - $10,000
- Electrical panel $1,500 - $4,000
- Water heater $1,500 - $6,000 (consider replacing traditional hot water heaters with tankless units)
- Additional labor and material costs to accommodate the new system locations (e.g., piping, wiring, ductwork, etc.)
Fill in your basement with sand, crushed stone, or gravel. A 3/4" stone provides better drainage than sand and maintains stability without settling over time. Filling your basement raises your home’s lowest floor elevation and could lower your flood insurance premiums by 15-20%. Obtain a new Elevation Certificate to document the changes for your insurance provider.
Installation: Requires a licensed professional to relocate mechanical systems to a higher floor, install flood vents, and fill the basement with proper drainage. Filling the basement adds weight. A structural engineer can determine if your foundation can handle the load.
Cost: For a 1,000 square foot basement, $3,000 - $10,000 (approximately $60 per cubic yard for material plus labor)
Useful life: Stone or gravel 50-100 years (the life of the home). Sand should be monitored for settling.
Abandon your first floor, move upstairs, and use the first floor for entry, storage, or parking. Although you lose living space, you lower your flood risk and can reduce your insurance premiums.
Installation: Requires a licensed professional. Floors and walls need to be replaced with flood-safe materials, mechanicals moved to an upper floor above the BFE, flood vents installed, and entrances elevated. Any planned changes should comply with National Flood Insurance Program requirements and local building codes, and cannot redirect water onto another property. Plan to move out temporarily while the space is being transformed, as work typically takes a few weeks to 90 days.
Cost: $10,000 - $100,000, depending on the extent of changes, materials used, and the size and intended use of the space.
Useful life: The life of the home.
Elevate your home on stilts, piers, or extended foundations at least two feet above the BFE to reduce your flood risk. Elevating your home can reduce insurance premiums 30% - 60% and increase the home’s value.
For buildings in FEMA’s Special Flood Hazard Area with a Standard Flood Insurance Policy that have experienced substantial or repetitive flood damage, check with your flood insurance provider to see if you qualify for Increased Cost of Compliance coverage up to $30,000 to elevate, relocate, demolish, or floodproof your building.
Installation: Requires a licensed professional and typically takes 6 to 12 weeks. The basement should either be filled or the floors and walls replaced with flood-safe materials. Mechanicals should be moved to an upper floor above the BFE, flood vents installed, and entrances elevated.
Cost: $25,000 - $100,000 or more, depending on the size of the building, the foundation type, and elevation height.
Useful life: 30-50 years
-
Still have questions? Contact:
Emergency Management
-
85 Bragdon Street
Boston, MA 02119
