10 Tips for Building a Flood-Proof House That's Up to Code

From seaside views to taking a daily dip in the lake, there's no question why we love to build homes by the water. However, many of these regions fall within a Special Flood Hazard Area (SFHA) designated by the Federal Emergency Management Agency (FEMA), which means your home is more susceptible to damage during a flood. While there's no way a home can ever be 100% flood-proof, FEMA and local agencies specify the best materials, structural conditions, and homebuilding tips to protect you and your home in the event of a large storm.

Once you choose a homebuilder with experience working with SFHAs, consider these 10 flood-proof home tips.

1. Learn Your BFE

When building a flood-proof home, you'll encounter a handful of acronyms and terminology. One of the most common is BFE, or base flood elevation. FEMA defines BFE as "the elevation of surface water resulting from a flood that has a 1% chance of equaling or exceeding that level in any given year." 

In this case, a 1% chance is more than enough of a threat to take special actions to protect your home. Doing so will also keep your insurance rates down. The National Flood Insurance Program (NFIP) will use the BFE of your property to set standards and propose insurance rates. 

For example, the lowest floor of your home—any fully enclosed living or storage space—must sit above the BFE. Areas below the BFE, such as garages or columns that raise your foundation, must be made of approved flood-resistant materials.

2. Opt for Flood-Resistant Materials

The NFIP categorizes common building materials into five classes based on their resistance to floodwaters. Keep in mind that these recommendations are the base-level requirements for living in an SFHA. Even if your home is only mildly susceptible to flooding, highly-rated materials may help lower your flood insurance rates and provide peace of mind during a rough storm season.

Any materials below the BFE must fall into class 4 or 5 to meet compliance. Here's a quick breakdown of what each class means:

• Class 5: Resistant against significant damage (beyond cosmetic) in moving floodwaters. These are used for exterior and partially enclosed areas.

• Class 4: Resistant against floodwaters, but not likely moving waters. It is possible to clean them after exposure to dangerous pollutants.

• Class 3: Only resistant to damage when submerged in clean water.

• Class 2: Cannot survive damage from clean water or floodwaters and should remain dry.

• Class 1: Cannot survive when exposed to either type of water or a high moisture level.

While FEMA provides a full list, some level 4 and 5 materials include:

• Brick

• Cast stone

• Cement board

• Preservative-treated borate

• Marine-grade plywood

• Commingled plastic lumber with 80%–90% polyethylene

• Steel trusses and beams

• Solid, decay-resistant wood beams

• Mortared ceramic and porcelain tile

• Glass tile

3. Raise Your Home

Photo: dhvstockphoto / Adobe Stock

With flood zones expanding, raising your home and keeping the lowest floor above the BFE is becoming more common. The NFIP defines the "lowest floor" as the lowest enclosed area. You cannot use anything below here for a living space or electrical and mechanical equipment. In other words, it's not your traditional basement or storage area.

Raising an existing home can cost up to $24,000, so it's important to consider this option during the initial construction. Raised homes sit on reinforced masonry materials, such as concrete or steel columns. You can also opt for approved class 4 or 5 types of wood to raise a home.

4. Consider Dry Floodproofing

Also called dry floodproofing, dry proofing includes any series of steps that ensure your home is watertight. Different methods of dry proofing include placing heavy plastic along the exterior of your home, adding floor shields over windows and doors, and using sealants in vulnerable areas around the home. 

Dry proofing doesn’t completely prevent flooding exposure, but it reduces your home’s vulnerability to floodwater. It’s best for people who live in areas that don’t experience excessively deep flood conditions and those whose homes have concrete or solid brick walls. 

5. Relocate Utility Appliances

Hot water heaters, furnaces, and major electrical systems have to be above the BFE in flood-prone areas. If the appliances sit below the lowest level of your home, contact your local heating specialist or plumber to discuss raising them. For example, you can avoid a water heater catastrophe by elevating it off the ground or installing it on a higher floor.

6. Choose the Right Insulation

Fortifying your walls against hydrostatic pressure can both keep water outside your home and protect against irreparable water damage in the wall's interior. Based on FEMA's regulations, opt for insulation materials that fall within classes 4 or 5. These include:

• Sprayed polyurethane foam

• Closed-cell plastic foams

• Formed-in-place plastic flooring

7. Landscape With Proper Drainage

Photo: bilanol / Adobe Stock

Regrading a sloped lawn or adding supporting drainage will help direct water away from your home and into the local storm drains. Installing landscape drainage costs an average of about $4,600, depending on the type of system you choose for your lawn. Lawn drainage systems include:

• French drains

• Trench drains

• Underground downspouts

• Yard inlets

• Concrete or plastic catch basins

8. Install a Sewage Backflow Preventer

FEMA also recommends installing a backflow preventer if sewage starts heading in the wrong direction during a flood. Backflow preventers, with their floaters and flap mechanism, prevent sewage from entering your home because they control whether the flap opens or closes. When there isn’t sewage backup, the flap remains open. If there is sewage backup, the floaters close the flap, preventing sewage backup from getting into your house.

Keeping sewage at bay is necessary to keep hazardous toxins away from your home and drinking water. Without a backflow preventer, wastewater may enter your home through many water sources, including tubs, sinks, and toilets. This can create serious health risks because sewage contains harmful bacteria and viruses that could cause diseases.

9. Reinforce the Basement

While most homes in flood-prone areas must legally raise the house above the BFE, you may still opt for a basement in less-threatened areas. In this case, there are several steps you can take to prevent basement flooding. Seal the interior of your walls with waterproof paint and install a sump pump to control minor floods. 

FEMA also sets standards for foundation flood vents that allow water to escape should you experience a large flood. You can also support your basement and crawl space by properly draining and grading your landscape and directing gutter downspouts at least 3 feet away from your foundation.

10. Hire an Experienced Team

Most importantly, you don't need to go this alone. If you live in an SHFA, FEMA can assign you a floodplain manager. You can also hire local homebuilders with flood-proofing experience, particularly local specialists in landscape drainage and grading or local basement waterproofers.