60.3(c)(7): Lowest Floor Elevation, Zone AO

60.3(c)(7) covers structures in Zone AO, and states that the elevation for the lowest floor must be elevated above the highest adjacent natural grade by the depth number specified in feet on the FIRM or a minimum of 2 feet if no depth number is specified.

This graphic of a building shows the highest adjacent natural grade.

It is important to remember that it is the highest adjacent natural grade prior to the start of construction, not after the site has been re-graded.

Another permissible elevation technique is to use perimeter walls with lower enclosed areas.

Graphic illustration of a two foot elevation on fill. Labeled are LFE (lowest floor elevation) 2ft fill dirt, and highest adjacent natural grade (natural grade prior to construction)
Elevation could be attained by any appropriate method previously listed (i.e. on properly designed perimeter walls, piles, piers, etc.).