The City of Key West, Florida

The Southernmost City in the Continental United States



The following are excerpts from the FEMA and engineering publications relevant to installing pools and spas in regulated flood zones. For the full publication, click on the link within each title.

Important Note:  For V-zones, remember to consider surrounding decks/slabs.  Slabs in these zones are limited to a thickness of four inches (4"), and must be free of all reinforcement (no rebar nor wire mesh).  FEMA doesn't want such slabs hydroplaning nor flipping which would cause damage to nearby buildings.  Keeping them less than 4" thick and free of reinforcement allows these slabs to crumble into chunks that will settle rather than travel.

FEMA's Coastal Construction Manual (FEMA 55)

"The design and placement of swimming pools can affect the performance of adjacent buildings. In-ground and above-ground (but below the DFE) pools should not be structurally attached to buildings. An attached pool can transfer flood loads to the building. Building foundation designs should also account for the effects of non-attached but adjacent pools: increased flow velocities, wave runup, wave reflection, and scour that can result from the redirection of flow by the pool. In addition, swimming pools should not be installed in enclosures below elevated buildings." 


ASCE/SEI 24-05 Section 9.5 POOLS

In-ground and above-ground pools shall be designed to withstand all flood-related loads and load combinations.

Pools that are structurally connected to structures shall be designed to function as a continuation of the building or structure.

In Coastal High Hazard Areas (V-zones), Coastal A Zones, and other High Risk Flood Hazard Areas, pools shall

1. Be elevated so that the lowest horizontal structural member is elevated as required in Section 4.4 (Base Flood Elevation plus one-foot); or

2. Be designed and constructed to break away during design flood conditions without producing debris capable of causing significant damage to any structure; or

3. Be sited to remain in the ground during design flood conditions without obstructing flow that results in damage to any structure.

Swimming Pools and Spas [FEMA Technical Bulletin 5]

Page 2: "Any construction element that is structurally dependent on, that is attached to, or upon which a V zone building depends, is considered to be part of that building and must meet the requirements of Sections 60.3(e)(4), (5), and (6). If any of these elements are attached to the building and located below the lowest horizontal structural member of the building, they may constitute an obstruction and may be prohibited. The attachment of any feature that is prohibited by NFIP regulations to an otherwise compliant building will result in a significantly higher flood insurance premium because of the increased risk of damage to the building. Further, if a community is found to have a pattern and practice of failing to address such violations, the NFIP may exercise its authority to place the community on probation or under suspension, which affects the cost and availability of Federal flood insurance.

Construction elements outside the perimeter (footprint) of and not attached to a coastal building (such as bulkheads, swimming pools, and accessory structures) and site development practices (e.g., the addition of fill) may alter the physical characteristics of flooding or significantly increase wave or debris impact forces affecting nearby buildings. As part of the certification process for V zone buildings, the design professional must consider the effects that these elements and practices will have on the building in question and on nearby buildings.

Construction elements and practices that will increase flood-related loadings on the building (and that are not specifically prohibited by the NFIP regulations) may be constructed if the impacted buildings are designed to withstand the additional flood and wave forces. Increased foundation element embedment depth, size, and number might be employed to compensate for increased flood forces. Such compensatory design calculations must be made by the registered design professional, who must provide a V zone certification for the structure prior to construction."

Page 16: For most circumstances and for small, low-rise V zone structures (including residences), the first alternative of frangible slabs should be employed. This alternative is also appropriate for other uses of slabs such as pool decks, sidewalks, and patios. Figure 13 illustrates one possible design for such a slab.

Page 26:  "Swimming Pools and Spas" - Pools and spas are allowed adjacent to coastal buildings only if these amenities will not act as obstructions that lead to damage to nearby buildings. This effectively means that most pools and spas must be installed in-ground (either frangible or immovable), or completely elevated above the BFE. This constraint applies where the ground level is below, at, or above the BFE.

Two primary considerations are related to the placement of swimming pools and spas under or adjacent to buildings in V zones:

  • Whether the pool and/or spa configuration is subject to NFIP use limitations for enclosed areas under elevated buildings, and
  • Whether the pool or spa will lead to increased flood loads on buildings or exacerbate scour and erosion near buildings.

The NFIP permits a swimming pool or spa to be placed beneath an elevated building only if the top of the pool/spa and accompanying deck or walkway are flush with the existing grade, and only if the space around the pool/spa remains unenclosed. However, some states and communities may prohibit restrict pools and spas beneath elevated buildings -- designers should check with the jurisdiction for any additional requirements.

The NFIP limits the use of enclosures to parking of vehicles, building access, and storage. Because pools and spas are for recreational use, they are not allowed to be enclosed, even if enclosed by glass or breakaway walls. Use of lattice and insect screening around pools and spas is permitted.

Registered design professionals must certify to local officials that a pool or spa beneath or near a V zone building will not be subject to flotation or displacement that will damage building foundations during a coastal flood. Figure 18 shows a case where a spa was displaced and likely caused failure of two piles that supported an elevated deck. Pools, pool decks, and walkways that are placed under or adjacent to coastal buildings must be structurally independent of the building and its foundation.


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