Flood Zone A vs. AE: What's the Difference?

Zone A and Zone AE are both Special Flood Hazard Areas with at least a 1% annual chance of flooding, often called the 100-year floodplain. The difference between them comes down to one number: Zone AE has a published Base Flood Elevation from a detailed FEMA study, and Zone A does not.

This article covers what each zone means, why the missing BFE in Zone A matters for an elevation certificate, and what the difference means for getting a flood insurance quote.

What Zone A Means

Zone A is a Special Flood Hazard Area where FEMA has not completed a detailed hydraulic study. The flood hazard is real and mapped, but no Base Flood Elevation has been published for the area.

• No BFE on the map. Without a detailed study, FEMA has not calculated a specific elevation that the flood is expected to reach.
• Still inside the 1% annual chance floodplain. The absence of a BFE does not mean the risk is lower than AE; it means less study has been done.
• Common in smaller or less-studied watersheds. Zone A often appears on streams and drainage areas that have not had the same level of engineering analysis as larger, mapped rivers.
• Can still convert to AE later. When FEMA or a local community completes a new study for an area, a Zone A designation can be updated to AE with a published BFE on the next map revision.

What Zone AE Means

Zone AE is a Special Flood Hazard Area where FEMA has completed a detailed study and published a Base Flood Elevation for the area.

• BFE is published on the map. Item B9 on an elevation certificate reflects this number when the property sits in an AE zone.
• Elevations can be compared directly. A surveyor can measure the building and compare it to a specific published number.
• AE has mostly replaced the older A1–A30 zones. Older maps used numbered A zones for areas with a published BFE; AE is the modern version of the same idea.

Why the Difference Matters for Elevation Certificates

An elevation certificate measures a building against the Base Flood Elevation. In an AE zone, that BFE is printed on the map, so Item B9 of the certificate is filled in and the surveyor's measurements in Section C can be compared to it directly.

In a Zone A property, B9 is often left blank because no BFE has been published. When that happens, the surveyor may have measured the building against a different reference, such as a locally available study or an approximate method, and that should be noted on the certificate. A blank B9 is expected in Zone A. It is not a sign that the certificate is incomplete.

Why the Difference Matters for Your Quote

Sterling does not require an elevation certificate to quote, in either zone. Without one, a quote can be based on the flood map and the foundation type.

When a certificate is available, an AE zone's published BFE gives an underwriter a direct comparison to the building's elevation. A Zone A property without a BFE gives the underwriter less to measure against, even with a certificate in hand, which is one reason Zone A properties are more often reviewed by hand rather than quoted instantly. A certificate obtained later, in either zone, can change the picture once it is submitted.

Common Mistakes with Zone A and AE

• Assuming Zone A is lower risk than AE. Both are Special Flood Hazard Areas with at least a 1% annual chance of flooding; the difference is the amount of study done, not the level of risk.
• Expecting a filled-in B9 on a Zone A certificate. A blank BFE field is normal when no detailed study exists.
• Using an outdated BFE after a map update. If the community's flood map has been revised, confirm the current BFE rather than relying on an older certificate.
• Confusing Zone A with Zone X. Zone A is inside the Special Flood Hazard Area; Zone X is not.

Pro Tips from Sterling Flood Underwriters

If you're in Zone A, ask your local floodplain administrator whether an advisory or interim BFE exists. Many communities have one even when FEMA's published map does not.

Send whatever elevation information you have, even if it's partial. A surveyor's measurements without a published BFE to compare them to are still useful.

Get a Quote

Whether your property sits in Zone A or Zone AE, a quote does not require an elevation certificate to get started. Get a flood insurance quote from Sterling Flood.

Frequently Asked Questions

What is the difference between Zone A and Zone AE?

Both are Special Flood Hazard Areas with at least a 1% annual chance of flooding. Zone AE has a published Base Flood Elevation from a detailed FEMA study; Zone A does not.

Do I need an elevation certificate in Zone AE?

Sterling does not require an elevation certificate to quote in Zone AE or Zone A. When one is available, it gives the underwriter measured numbers to compare against the published BFE.

Is Zone A less risky than Zone AE?

No. Both carry at least a 1% annual chance of flooding. The difference is whether a detailed study and Base Flood Elevation have been published, not the underlying risk.

What if I don't know my flood zone?

Your flood zone is shown on FEMA's Flood Insurance Rate Map for your address. A local floodplain administrator or surveyor can also confirm it.