FAQs

Illustrations can be found in the following publications: (FEMA Technical Bulletin 9) https://www.fema.gov/sites/default/files/documents/fema_nfip-technical-bulletin-9-09292021.pdf

(FEMA P-55, Volume I) https://www.fema.gov/sites/default/files/2020-08/fema55_voli_combined.pdf

No. Utilities, including electrical wiring, switches, outlets, breaker boxes, power meters, plumbing, conduits, and ventilation ducts, are not to be placed in or attached to breakaway wall panels. Building supply lines and other utility fixtures, such as light switches or electrical outlets, may be attached to the sheltered side of vertical foundation members as allowed by applicable building codes and floodplain management regulations (which generally require that utilities be elevated above the BFE). Breakaway walls are discussed in TB-9 and in ASCE 24 and FEMA Mitigation Assessment Team (MAT) observations described below:

• ASCE 24-14, Section 4.6.1 Breakaway Walls. Requires breakaway walls to fail before or during base flood conditions without imparting loads on foundations and without producing damaging debris. Specifies that utilities and equipment must not be mounted on, pass through, or be located along breakaway walls.
• MAT observations: All utility components that must be installed below the elevated structure must be flood damage-resistant, designed for flood forces, and attached to permanent structural elements. When utilities must be located below an elevated structure, the components should be placed on the protected side of a foundation member on the side opposite to the anticipated direction of flow and wave approach.

No. In Coastal areas, DFE is the bottom of lowest horizontal structural member, therefore there should be no “solid walls” between that and the top of the breakaway wall.

Confirmed. Breakaway walls are not a requirement on open foundations. A garage floor/slab below the BFE can remain open, be enclosed by insect screening or lattice work, or enclosed by breakaway walls. Also, since breakaway walls are not structural, the living area above the garage will have to be supported by structural piles/piers/columns.

Yes. The elevation must be referenced to the bottom of the lowest horizontal structural member if the structure is located in a V Zone or Coastal A Zone. If the structure is located outside of the V and Coastal A Zones, then the elevation can be referenced to the top of the floor.

Prescriptive breakaway walls are code compliant, with resistance between 10 and 20 psf. If the breakaway resistance exceeds 20 psf, then an engineer must certify that the wall will fail under base load loads with no damage to the structure.

Frangible building elements are ones that are designed to break into small pieces that will not cause an obstruction to flow or damage other structures. Examples of frangible elements include breakaway walls as well as small non-structural slabs with saw-cut joints beneath elevated coastal buildings.

Yes, this is a FEMA concern regarding breakaway walls. Additionally, ASCE 24-14, Section 4.6.1 (Breakaway Walls) requires breakaway walls to fail before or during base flood conditions without impacting loads on foundations and without producing damaging debris.

A list of utility services, machinery and equipment that must be elevated to the DFE can be found in FEMA P-348, Protecting Building Utility Systems from Flood Damage, Edition 2, February 2017. If these services, machinery and equipment cannot be elevated, then the NFIP states they must be designed and constructed to prevent entry and accumulation of floodwaters. While this is very difficult to achieve, examples of FEMA-acceptable ‘floodproofing’ techniques may include placement of below-BFE utilities in a flood-resistant enclosure such as a low floodwall or a large floodproof vault.

TB-9 (3.3): The 2015 and later editions of the IRC and the 2014 edition of ASCE 24 require flood openings in breakaway walls in both Zone A (including Coastal A Zones) and Zone V. Breakaway walls with flood openings must be designed to fail under the base flood specified by the NFIP regulations and building codes and standards. The NFIP regulations do not require flood openings in breakaway walls of enclosures below elevated buildings in Zone V but require flood openings in walls of enclosures below elevated buildings in Zone A, even when breakaway walls are specified. See NFIP Technical Bulletin 1, Requirements for Flood Openings in Foundation Walls and Walls
of Enclosures.

No. We are not aware of any additional EC boxes that need to address breakaway wall concerns.

Yes. According to ASCE 24-14 (9.3): In Coastal High Hazard Areas, Coastal A Zones, and other High Risk Flood Hazard Areas, concrete slabs used as parking pads, enclosure floors, landings, decks, walkways, patios, and similar uses shall be permitted beneath or adjacent to structures, provided the concrete slabs are designed and constructed as described below:

1. To be structurally independent of the primary foundation system of the structure, to not transfer flood loads to the main structure, and to be frangible and break away to minimize the debris capable of causing significant damage to any structure. Reinforcing of concrete slabs, including welded wire reinforcement, shall not be used to minimize the potential for concrete slabs being a source of debris. Slabs shall not have turned down edges, and maximum slab thickness shall not exceed 4 in.; or
2. To be self-supporting structural slabs capable of remaining intact and functional under base flood conditions, including expected erosion or uplift pressures, and the main structure shall be capable of resisting any added flood loads and effects of local scour due to the presence of the slabs.

The Coastal Construction Manual course addresses this topic.

Per TB-4 (3.2), elevator shafts must resist flood loads. In Zone A, shafts are not required to have flood openings; in Zone V and Coastal A Zones, shafts are not required to have breakaway walls. In addition, (6.1) to minimize flood damage, elevator shafts/enclosures must be designed to resist hydrostatic, hydrodynamic, and debris impact forces, as well as erosion, scour, and waves, particularly in Zone V. To reduce exposure of elevators to flood loads, a common practice is to construct reinforced masonry block or reinforced concrete elevator shafts and locate them on the landward side of buildings in coastal areas and on the downstream side of buildings in riverine floodplains. Furthermore, designs for nearby or adjacent structural elements of the building should take into account the impacts of obstructed flow.

Per FEMA P-348 (3.2.3): although difficult to achieve, an alternative provided by NFIP regulations allows equipment to be located below the BFE, provided that the equipment is designed, constructed, and installed to “prevent water from entering or accumulating within the components during conditions of flooding.” Please note that specially designed equipment is not permitted below the BFE in buildings located in coastal high-hazard areas (Zone V) due to a requirement that space below such buildings be free of obstructions.

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