How do I find the BFE of a property?

The base flood elevation (BFE) is the height floodwater is expected to reach during the base flood: the flood that has a one percent chance of being equalled or exceeded in any given year, the one people call the hundred-year flood. FEMA publishes it for the areas it has studied in detail, on the Flood Insurance Rate Map (FIRM), as a number of feet above a fixed vertical datum. Whether a building's lowest floor sits above or below that number is what most of flood risk, most of the flood-insurance conversation and all of the floodplain building rules turn on.

There are five places to find it. They are listed in the order most people should try them, which is also roughly the order of effort.

#1. FEMA's Flood Map Service Center

The Map Service Center at msc.fema.gov is the official source. Type the property address into the search, and it returns the FIRM panel the property falls on, with the effective date of that panel and a "dynamic map" view centred on the address. From there you can print a FIRMette, a letter-size extract of the panel around the property.

On the map, the BFE appears in two forms depending on the kind of flooding:

• In riverine AE zones, as wavy lines crossing the floodplain, each labelled with an elevation. Unless the property sits right on a line, the BFE is interpolated between the lines on either side, measured along the direction of flow.
• In coastal and lake zones, as part of the zone label itself, in the form "ZONE AE (EL 12)" or "ZONE VE (EL 14)", one value for the whole shaded area.

If the property is in an area shaded as Zone A with no elevation shown, FEMA has mapped the floodplain by approximate methods and has not determined a BFE for it. Skip to the section on Zone A below.

Check the panel's effective date while you are there. Maps are revised, and a preliminary map for the area may already show a different zone or elevation; the MSC lists preliminary products alongside effective ones.

#2. The interactive flood hazard layer

FEMA also publishes the same data as the National Flood Hazard Layer, an interactive map at hazards.fema.gov. Clicking a location returns the flood zone and, where the layer carries a static BFE for that area, the elevation. In riverine areas the BFE is a separate line layer rather than an attribute of the zone, so you may still be reading the nearest line.

The flood zone lookup on this site reads the same layer for an address and returns the zone, whether it is inside a Special Flood Hazard Area, the static BFE where the layer has one, and the FIRM panel with its effective date. It is a quick way to triage an address; it does not replace the panel or a survey.

#3. The Flood Insurance Study

Behind every detailed FIRM is a Flood Insurance Study (FIS), the engineering report for the community. It carries the flood profiles, elevation plotted against distance along each studied stream, and the floodway data tables with a BFE at every cross-section. Where the map shows whole feet, the study shows tenths, and where the map leaves you interpolating between two lines, the profile gives you the value at the exact river station.

The FIS is available from the Map Service Center under the community's products. It is the right source when a foot matters, which it does whenever a building sits close to the line.

#4. An elevation certificate

An elevation certificate is FEMA's form for recording how a specific building relates to the flood map. Section A identifies the property and building; Section B records the flood map data, including the BFE; Section C records the surveyed elevations of the building itself (the lowest floor, the lowest adjacent grade, machinery and equipment) and the datum they are measured in. Section C needs a licensed surveyor, engineer or architect. In a Zone A with no BFE, or a Zone AO, the owner or the community's floodplain official can complete a shorter section instead. It is the only document that answers the question the BFE is really for, which is whether this building is above the water or below it.

If the property has changed hands or been insured before, a certificate may already exist. Ask, in this order: the seller or current owner, the current insurance agent, the lender, and the community's floodplain office, which keeps elevation records for buildings constructed since the community joined the National Flood Insurance Program. If none turns up, commissioning one is a survey job.

#5. The local floodplain administrator

Every community that participates in the NFIP has a floodplain administrator, usually in the building or planning department. They can give you the BFE for a parcel, tell you whether a map amendment or revision has changed it since the panel was printed, say what elevation new construction must be built to (the BFE, plus any freeboard the community adds on top, often a foot or two), and pull any elevation certificate on file. For a property in Zone A with no published elevation, they are often the only source of a number.

#Reading what you find

The zone comes first. The letter tells you whether a BFE exists at all.

The datum matters. Elevations are meaningless without the reference they are measured from. Current maps use NAVD88; older maps and older elevation certificates may use NGVD29, and the difference between the two varies by location and can exceed a foot. Never compare a BFE in one datum with a surveyed floor elevation in the other without converting; the National Geodetic Survey publishes the conversion.

Map values are rounded. A BFE printed on the panel is a whole number of feet. The study and a certificate carry tenths. A building that reads as "at the BFE" on the map can be above or below it by the study.

#When there is no BFE: Zone A

An unnumbered A zone means FEMA established the floodplain boundary without a detailed study, so there is no published elevation. That does not mean nobody has one. The community may hold a locally produced study, a state agency may have modelled the reach, or a developer's engineer may have established an elevation for a subdivision. FEMA's own guidance for these areas is to use the best available data, and the floodplain administrator is where to ask for it. Failing all of that, an engineer can estimate a BFE from the topography and the stream, which is what an application to amend the map for a Zone A property requires.

#What to do with the number

Compare it with the building. The lowest floor elevation from a certificate against the BFE gives the freeboard, positive or negative. A building a foot above the BFE and a building a foot below are different risks, different premiums and different conversations with a lender.

For flood insurance. The National Flood Insurance Program stopped rating primarily on BFE when it moved to its current rating method, Risk Rating 2.0, which applied to new policies from October 2021 and to renewals from April 2022. An elevation certificate is no longer required to buy a policy, but one can still be submitted, and for a building that sits above the BFE it can lower the premium. Private flood markets set their own rules and most of them want the elevation.

For the lender. The mandatory purchase requirement is triggered by the zone, not the elevation: a federally backed mortgage on a building inside the Special Flood Hazard Area needs flood insurance whatever the BFE says. Where the building's lowest adjacent grade is at or above the BFE, a Letter of Map Amendment can remove the structure from the SFHA, which removes the requirement.

For building work. Local ordinance requires new construction and substantial improvements in the floodplain to be elevated to at least the BFE, plus any freeboard the community requires. Anyone planning an addition, a rebuild or a conversion needs the number before the drawings.

#Where this fits in a property submission

For an agent, the BFE is one line in the construction, occupancy, protection and exposure picture on a commercial property application. The ACORD 140 has no dedicated flood field, so the zone usually goes in the remarks, and the property hazard snapshot pulls the zone alongside hail history, wildfire risk and the nearest fire station for an address in one card. The ACORD 140 explainer walks the rest of the form.

#Related

• Free property tools
• ACORD 140 explained