Flood zone AE: can I build, and how high?

What the letters mean

FEMA, the federal emergency agency, draws flood maps for the whole country. Every lot falls in a zone.

• Zones starting with A or V (A, AE, AH, AO, VE) are the high-risk areas. They are expected to flood in a storm that has a 1 percent chance of happening in any year. People call it the 100-year flood.
• Zone VE is on the coast, where waves add to the flood. Its rules are the strictest.
• Shaded zone X is moderate risk, between the 100-year and the 500-year flood.
• Unshaded zone X is minimal risk.

Much of coastal South Florida is in zone AE. It is normal here, and new homes are built in it every year.

The number that matters

In zones AE and VE, the map gives a height next to the letters, for example “AE (EL 8)”. This is the base flood elevation: the level, in feet, that the water of that flood is expected to reach.

What counts for your project is the gap between that number and the height of your ground. A surveyor measures your ground and writes it in a document called an elevation certificate.

How high you must build

In Florida, the building code asks that the lowest floor of a new home in an A zone sits at or above the base flood elevation plus 1 foot. Your city can ask for more, and some do.

In zone VE the house must also stand on piles or columns, with the space under it left open so water can pass.

So if the map says 8 feet and your ground is at 5 feet, the floor of the house will be at least 4 feet above the ground.

What it changes in a project

• Cost. Raising the floor means more fill or a taller foundation, plus stairs and ramps.
• Design. In some cities the height limit is measured from the flood level, in others from the ground. This can change how many floors fit.
• Insurance. Lenders require flood insurance in the high-risk zones when the loan is federally backed. A higher floor usually means a lower premium for the buyer.

A flood zone rarely stops a project. It changes the numbers, and a serious buyer has already counted them in his offer.

Check your lot

You can look up any address for free on the FEMA Flood Map Service Center. The maps are revised from time to time, so check the current one.

Our Land Check shows the flood zone of your lot next to its area and its zoning. Then read what can I build on my lot? for the zoning side.