How do I find the base flood elevation for a property?
Find the property on the effective flood map and read the base flood elevation printed for its zone, then confirm the number in the Flood Insurance Study's flood profile for that reach, which is the source the map is drawn from. The elevation is the water level a 1%-annual-chance flood is expected to reach, stated against a named vertical datum. It exists only for the zones that carry one (AE, AH, VE and their numbered relatives). An unnumbered Zone A has no published elevation, and Zone X has none because the property is mapped outside the floodplain.
Reviewed by Spatia's editor on 2026-09-30; sources checked 2026-09-30.
The mistake almost everyone makes
Reading the base flood elevation as the height of the water above the ground. It is an elevation, a height above a datum, not a depth: the depth at the house is that elevation minus the ground elevation at the house, and the ground elevation is what a survey gives you. And the number has a datum. Older maps use NGVD 29, newer ones NAVD 88, and the two can differ by more than a foot in the same place, so an elevation certificate and a map that name different datums are not comparable until one is converted. The base flood elevation is the top of the water; what matters for a building is where its lowest floor sits relative to that top.
How to check it
Locate the property on the effective FIRM
Look the address up on FEMA's Flood Map Service Center, find the building footprint on the panel, and read the zone under it. In AE and VE zones the base flood elevation is printed along the zone, rounded to the whole foot; in AH it is an elevation and in AO it is a depth, which is a different kind of number.
Read the Flood Insurance Study for the exact value
The study report carries the flood profiles and the data tables the map was drawn from, to the tenth of a foot, at lettered cross-sections along each studied reach. Find the cross-sections upstream and downstream of the property and read the profile between them. The study is the instrument; the map is a rendering of it.
Note the vertical datum before comparing anything
The map and the study name their datum. An elevation certificate, a survey or a terrain model on a different datum has to be converted before it is subtracted from the base flood elevation, and the conversion carries its own uncertainty; record it.
If the zone has no published elevation
In an unnumbered Zone A the community may hold best-available elevation data from another study, and its floodplain administrator will say what it will accept. Where there is none, establishing one is an engineer's work and a condition of the permit.
Turn the elevation into a depth with a survey
A licensed surveyor's elevation certificate records the lowest floor and the lowest adjacent grade against the same datum as the map. The difference between those and the base flood elevation, plus the community's freeboard, is the number a permit and an insurance rating are built on.
What this still does not tell you
- It is not an elevation certificate and does not establish where the building's floor sits.
- The map's printed elevation is rounded; the study carries the exact value, and both name a datum that must match anything they are compared with.
- In an unnumbered Zone A there is no published elevation, and none can be read from a map.
- It is not a substitute for the Flood Insurance Study, the floodplain administrator or a licensed surveyor, and it is not engineering advice.
Who actually decides
- FEMA — base flood elevation
- FEMA — the Flood Insurance Study, which carries the flood profiles
- FEMA Flood Map Service Center — the effective FIRM and study
- Your community's floodplain administrator, and a licensed surveyor — the elevation the permit accepts, and the certificate that measures the building against it