The Florida Division of Emergency Management, State Floodplain Management Office offers the comments below. We also encourage review of the CCCL Fact Sheet prepared for the Florida Building Commission by Building A Safer Florida (https://www.floridadisaster.org/dem/mitigation/floodplain/ (Community Resources/FBC Resources),
1. Sec. R322 applies to dwellings within the scope of the FBC, Residential structures that are in the flood hazard area governed by in R322. Table R301.2(1) footnote (g) refers to local floodplain management ordinances for adoption of maps and studies.
2. Regarding the specific question about R322.1.4, before looking at that section and which flood elevation to use, see Sec. R322.1.1, structures seaward of the CCCL. Sec. R322.1.4 identifies the “predicted forces of a 100-year storm event in accordance with Section 3109 … and “the more restrictive provisions shall govern.”
3. The following is DEM’s understanding of the requirements of Sec. 3109 pertinent to the inquiry:
a. Sec. 3109 applies to all sites seaward of the CCCL, even those locations that are in FEMA Zone X.
b. Sec. 3109 requires use of the higher of the elevation in ASCE 24, local elevation if more freeboard adopted, or the DEP 100-year storm elevation.
c. Sec. 3109 has requirements that apply between the Base Flood Elevation (FEMA) and the DEP 100-year storm elevation. See especially Sec. 3109.3.4 (walls and enclosures).
d. Breakaway walls are required when there is an enclosure below the DEP 100-year storm elevation and above the ASCE 24 elevation, or locally adopted elevation if higher and/or more freeboard is required, and uses of those enclosures are limited to those in the definition for “allowable uses.”
e. Breakaway walls, with flood openings, are required if there is an enclosure below the ASCE 24 elevation, or local elevation if higher and/or more freeboard is required, and uses of the enclosure are limited to parking, storage, and building access.
f. Sec. 3109.3.2 requires foundations to be piles or columns and “shallow foundations and stemwalls are not permitted.”
g. Sec. 3109.3.5 allows structural slabs that don’t breakaway if designed by an engineer.