Should You Add Flood Vents to Your Home?

Flood vents can protect your home from damage during heavy rainstorms, hurricanes and floods. Here's what you need to know about them.

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If you live in the Great Lakes region, congratulations. You’re among the least likely Americans to experience a natural disaster.

People on the Gulf Coast and Atlantic Seaboard, on the other hand, must be prepared for floods, while those on the West Coast watch out for wildfires and floods. Fires are terrifying, but floods are far more common and destructive, causing $3 billion in damage in the U.S. in 2021 alone.

Rising and flowing water during a flood can weaken and undermine a building’s foundation, eventually causing the structure to collapse. That’s why the National Flood Insurance Program (NFIP) requires flood vents in areas it designates as flood-prone.

Even if they aren’t required where you live, flood vents are a smart investment. According to Jon Sanborn, a San Diego real estate professional and founder of SD House Guys: “If your property is surrounded by large amounts of impermeable surfaces, such as pavement or concrete, then you should consider installing flood vents to help reduce the potential for water damage.”

So should you add flood vents to your home? Read on to find out

What Are Flood Vents?

Nathan Claire, a Florida-based real estate investor, says flood vents are specialized openings in foundation walls that allow water to flow freely through them. They equalize pressure on both sides, lowering the risk of structural failure.

The NFIP requires a flood vent be installed no more than one foot above the interior or exterior grade immediately below it. It must be below the base flood elevation (BFE), which the Federal Emergency Management Agency (FEMA) defines 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.” Consult FEMA’s flood maps┬áto find the BFE for your area.

There must be at least two flood vents in a foundation wall. If the area inside the building is subdivided, each section must have two.

The vents are sized according to the floor area of the building, with one square inch of venting area required for every square foot of floor space. According to this formula, the vents for a 2,000-square-foot house would be 2,000 square inches, or about 14 square feet.

How Do Flood Vents Work?

Allowing water to flow through the foundation reduces the buildup of hydrostatic pressure against the walls, which can cause them to crack or collapse during a flood. Sanborn says the water usually moves through a series of interconnected pipes or channels.

The vents open when the water level reaches a certain height. This prevents water from accumulating in the foundation and damaging your property. The vents can also be manually adjusted to ensure they remain closed until needed.

Who Should Have Flood Vents?

“Flood vents are typically installed in areas that are prone to flooding or in buildings that are located near bodies of water,” Claire says. “They are also commonly used in areas with high groundwater levels, such as coastal regions, where flooding can be particularly severe.”

NFIP regulations, as well as some local building codes, require flood vents in the foundation walls of any residential structure in Flood Zone A with its lowest floor situated above the BFE.

According to FEMA, Flood Zone A includes areas with a 1% chance of flooding in a single year and a 26% chance during a 30-year mortgage. You can look on FEMA’s map to see if your property qualifies.

Buildings with a basement and/or crawl space should have flood vents in the walls of these utility spaces.

Types of Flood Vents

Flood vents are technically the covers for the holes where water passes through. Claire says there are several types. The most common:

  • Mechanical vents: These open and close automatically. They typically use a float system or a pressure sensor to detect rising floodwaters and open the vents. Some may also be connected to a backup power source, like a battery or generator, to ensure they function during power outages.
  • Passive vents: These rely on the pressure of the rising water to open and close them.
  • Hybrid vents: These combine mechanical and passive elements to provide greater flexibility and reliability. A float system or pressure sensor detects rising floodwaters and opens the vents, then relies on the pressure of the water to keep them open.

How To Install Flood Vents

Flood vent covers can be installed over any existing opening in the foundation that meets the requirements, though installers usually have to make the opening themselves.

You need at least two openings. Each must meet the minimum size requirement for the building, and the bottom of each can’t be more than 12 inches from the ground. The vent can cover the opening from the outside or fit inside. Either way, it’s typically held in place with construction adhesive or another strong waterproof sealant.

It’s best to install flood vents during new construction because cutting openings in a concrete foundation can be challenging. The job is DIY-able for anyone with the right tools. However, if you opt for professional installation, you’ll pay about $700 for two vents. If you have a complex foundation that requires more than that, the cost is typically around $260 per vent.

Chris Deziel
Chris Deziel has been active in the building trades for more than 30 years. He helped build a small city in the Oregon desert from the ground up and helped establish two landscaping companies. He has worked as a carpenter, plumber and furniture refinisher. Deziel has been writing DIY articles since 2010 and has worked as an online consultant, most recently with Home Depot's Pro Referral service. His work has been published on Landlordology, Apartments.com and Hunker. Deziel has also published science content and is an avid musician.