Base flood elevation, freeboard & flood maps, explained

When someone tells you a house has to be raised "to code," what they really mean is a specific height above a line on a map. That line, and the margin added on top of it, decide how high your lowest floor has to sit. Here's how those numbers are built.

Base Flood Elevation (BFE)

The Base Flood Elevation is the height that floodwater is expected to reach during the "base flood," the flood that has a 1% chance of happening in any given year, often called the 100-year flood. It's expressed as an elevation above a fixed reference (feet above sea level), not as a depth of water. FEMA publishes the BFE for your area on its flood maps. On the Jersey Shore, BFEs reflect both tidal surge and wave action, which is why they can be higher on an oceanfront block than a few streets inland.

Freeboard and Design Flood Elevation (DFE)

Freeboard is a safety margin added above the BFE. Building exactly to the BFE leaves no cushion for a storm that runs higher than the model or for maps that lag behind rising seas, so New Jersey and many towns require you to build a foot or more higher. BFE plus that required freeboard gives you the Design Flood Elevation (DFE): the height your lowest floor actually has to meet.

In 2026 New Jersey raised the coastal design flood elevation significantly under its new REAL rule, pushing many new and substantially improved shore homes to roughly four feet above the BFE. That change is big enough that we cover it on its own page: the REAL "4-foot rule" explained.

Flood zones you'll see on the shore

Your flood map assigns a zone that tells you both your risk and the construction rules that apply:

• Zone VE (coastal high hazard). Exposed to waves of about three feet or more. The strictest zone: homes must sit on open pilings so waves can pass beneath, with no solid walls that would trap water.
• Coastal A / LiMWA. The "moderate wave" band just landward of VE (between the Limit of Moderate Wave Action and the rest of the AE zone). Increasingly built to near-VE standards because it still sees damaging waves.
• Zone AE. In the floodplain with a published BFE, but generally without the destructive wave action of VE. Elevation is required, though piers or other foundations may be allowed.
• Zone X (shaded/unshaded). Outside the mapped high-risk floodplain. Lower risk, though "outside the zone" is never the same as "no risk."

Where the maps come from, and why they change

FEMA publishes Flood Insurance Rate Maps (FIRMs) and updates them over time as coastlines, development, and modeling change. After Sandy, FEMA issued Advisory Base Flood Elevations and then preliminary maps that raised elevations across much of the shore before newer maps became effective. The practical lesson: your BFE is not permanent, and both FEMA's maps and New Jersey's state rules can move the target upward. Building with freeboard is how you stay ahead of the next revision instead of chasing it.

How to find your own numbers

• Look up your address on FEMA's Flood Map Service Center to find your zone and BFE.
• Ask your township's floodplain administrator for the local freeboard requirement and any zone specifics.
• Get an Elevation Certificate from a licensed surveyor. It records exactly how your home sits today relative to the BFE, which drives both your project and your insurance rate.

Once those numbers are in hand, the elevation itself is straightforward engineering. You can watch the idea in motion on our interactive elevation slider, which shows a home rising until its floor clears the flood line.