The purpose of this page is to define enclosures, a commonly used term in floodplain management.
Enclosures are enclosed walled in areas below the lowest floor of an elevated building. Enclosures below the Base Flood Elevation (BFE) may only be used for building access, vehicle parking, and storage. Enclosed areas below the lowest floor must be adequately anchored, built using flood resistant building material, and any utilities or service facilities must be designed and/or located to prevent flood damage. Flood insurance coverage for enclosures below the BFE is very limited.
In A Zones, fully enclosed areas below the lowest floor must be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing the entry and exit of floodwaters. Designs must meet certain minimum criteria for openings in the enclosure walls or be certified by a registered design professional.
In V Zones, the space below the lowest floor of a building shall be free of obstruction or constructed with non-supporting breakaway walls, open wood lattice work, or insect screening intended to collapse under wind and water loads without causing collapse, displacement, or other structural damage to the elevated portion of the building or supporting foundation system. Designs to meet this criteria must be certified by a registered design professional or meet certain minimum criteria for breakaway walls.
- 60.3 (a)(3) - Reasonably Safe from Flooding
- 60.3 (c)(5) Openings Requirement in A Zones
- 60.3 (e)(5) Breakaway Wall Requirement in V Zones
- IS-9 Managing Floodplain Development Through The National Flood Insurance Program (NFIP) (page 5-32 to 5-36)
- Openings in Foundation Walls and Walls of Enclosures (Technical Bulletin 1) (2008)
- Flood Damage-Resistant Materials Requirements (Technicl Bulletin 2) (2008)
- Below-Grade Parking Requirements (FIA-TB-6)
- Free-Of-Obstruction Requirements (Technical Bulletin 5) (2008)
- Design and Construction Guidance for Breakaway Walls Below Elevated Coastal Buildings (Technical Bulletin 9) (2008)
Special Topic Resources
- CRS Credit for Enclosure Limits
IS-9, Managing Floodplain Development Through the NFIP (Page 5-35, Storage)