The City of Key West, Florida

The Southernmost City in the Continental United States

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Breakaway Walls

In "V" type flood zones, enclosed areas below flood levels may be used to for minimal storage, parking and access to upper levels.  However, these areas must have breakaway walls. 

"V" zones are located along or near coastlines, where the "velocity" from breaking waves is considered most destructive, and where building codes have higher standards. (See How to Read Flood Maps)

These breakaway walls must be designed and certified by an Engineer to certain pressure tolerances, so when violent waters hit these walls they break-away from the building.

If these walls didn't break-away, the forces against them would be transmitted to the entire building, which could cause it to collapse.  Once these walls break-away, the water rolls back and forth under the building between the columns, exerting very little force upon the building.

Construction/Inspection Tips:

Breakaway wall inspections often fail for these reasons:

  • No utilities can be attached to or through these walls, such as: pipes, electrical wiring etc.
    • These walls can't break-away as designed if pipes and wires will tie them to the building.
  • Inside is finished
    • Breakaway walls are to be considered expendable, for the greater good of the building. Interior finishes makes these walls harder to break-away, and encourage occupancy where prohibited.
  • Free from obstructions 
    • If there's something big installed next to such a wall - freezer, refrigerator, heavy shelving etc., it'll prevent the wall from breaking-away.
  • Exterior siding is extended down to cover breakaway walls
    • See the damage photo below where siding was extended to these lower walls.
  • Plastic lattice is much too durable for below flood applications in type "V" flood zones.  
    • It won't break, and will collect a large amount of debris causing the wave action force to be transmitted to the entire building.  Wooden lattice will break more readily when struck by floating debris.

If designed properly, the following photograph shows how a ground floor enclosure with breakaway walls would/should look after a ravaging storm...

breakaway walls after

Breakaway Wall Fail

Notice that because this wall failed to break-away, the wave action was deflected upwards. The window was smashed and let flood waters inside.

A large obstruction can be seen behind the wall, preventing it from breaking-away.

Had it broken-away as designed, there likely wouldn't have been any damage to the livable area of this building.

breakaway-wall-fail

 

Helpful Publications & Forms:

V-Zone Certification Form (computer friendly version)

V-Zone Certification Form (paper version)

FEMA's Quick Fact Pamphlet on Breakaway Walls

FEMA's Technical Bulletin 9, Design and Construction Guidance for Breakaway Walls Below Elevated Coastal Buildings (2008)

Free-Of-Obstruction Requirements (Technical Bulletin 5) (2008)

Contact Us

Scott Fraser,
FEMA Coordinator/Floodplain Administrator
Building Department
1300 White St
Key West, FL 33040
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