FloodMapReview logo

FloodMapReview.com

LOMA and LOMR-F guidance

Glossary

Lowest Adjacent Grade (LAG)

Lowest Adjacent Grade is the lowest ground elevation touching a building's exterior, a critical measurement in LOMA applications.

Lowest Adjacent Grade, or LAG, is the lowest natural or finished ground elevation measured at the exterior perimeter of a structure. It is one of the most important measurements in LOMA and LOMR-F work because FEMA compares the LAG to the Base Flood Elevation to determine whether a property qualifies for removal from the SFHA.

Start Eligibility ReviewBrowse Guides

Key takeaways

LAG is measured at the lowest point where the ground touches the building foundation.
For a LOMA, the LAG must be at or above the BFE for the property to qualify.
The measurement is typically recorded on an Elevation Certificate by a licensed surveyor.
Even small differences between the LAG and BFE can determine whether a LOMA is approved or denied.

Why it matters

LAG is the single measurement most likely to determine LOMA eligibility.
Homeowners need to understand what is being measured and why it matters before hiring a surveyor.
Misunderstanding LAG vs. other elevation measurements can lead to confusion about LOMA outcomes.

Frequently asked questions

What is the difference between Lowest Adjacent Grade and Lowest Floor Elevation?

Lowest Adjacent Grade is the ground level at the outside of the building. Lowest Floor Elevation is the elevation of the lowest floor inside the building (including basements). FEMA uses LAG for LOMA determinations on structures, while Lowest Floor Elevation is more relevant for insurance rating and some LOMR-F applications.

How is LAG measured?

A licensed surveyor measures the LAG by identifying the lowest point where the natural or finished ground surface meets the building's exterior foundation. The measurement is recorded as an elevation referenced to a consistent vertical datum, typically NAVD88, and documented on an Elevation Certificate.

What if my LAG is below the BFE?

If your LAG is below the BFE, your property will not qualify for a standard LOMA based on the structure. Depending on the specifics, you may still have options — such as applying for a LOMA on the lot (not the structure) or exploring a LOMR-F if fill could raise the grade. A professional review can identify the best path forward.

Can landscaping or grading change my LAG?

Adding fill or regrading around your foundation can change the finished grade and therefore the LAG measurement. However, if the original ground was not naturally high enough, this would make the case a LOMR-F (fill-based) rather than a LOMA (natural ground). The distinction between natural grade and filled grade matters to FEMA.