The City of Key West, Florida

The Southernmost City in the Continental United States


Substantial Improvement FAQ



Important Note:  Each building needs its own Building Permit Application, even if they're on the same lot.  Only one set of plans is needed, not a set for each application. 


Q:What is the 50% rule?

A:  FEMA's Flood maps for Key West first became effective Dec. 31, 1974.  Buildings constructed after that date were required to be at certain elevations above sea level.  Existing buildings within regulated flood zones were grandfathered into the National Flood Insurance Program (NFIP) at their current elevations.  However, that grandfathered status ceases once the building has been renovated by half it's market value.  Once that threshold is reached, renovation plans must include elevating the home to current flood levels. 

Trivia: Actually, the first flood maps were effective circa 1970/71, back when the NFIP was administered by HUD. When FEMA took over, it had great difficulty discerning records for the early years of the program.  As a result, FEMA stipulated, that any community with flood maps having an effective date prior to Dec. 21, 1974 - such as Key West - would now be governed by this 1974 date rather than the earlier map dates. 


Q: What's a "regulated flood zone?"

A: FEMA has mapped flood zones across the city based upon the ground elevation of those areas.  Zones identifiers such as "AE", "AO", "VE" & "Coastal A" require that buildings within these flood zones are subject to special flood hazard building requirements.  Zones identified as "X" or "Shaded-X" are mapped as being above expected flood levels, so those special building requirements don't apply to buildings fully inside these type of flood zones. (See Online Flood Maps)


Q: How is the market value of my building determined in connection with the 50% rule?

A: It starts with the County Property Appraiser's value for the building (just the building's value [Market Improvement Value], not including the land value) before any work has been performed. Then 15% is added to that building value.  So... a building on the Property Appraiser that has a value at $100,000, would have a market value of $115,000.  This is called the Adjusted Property Appraiser's value.


Q: I believe my house is worth more than the Adjusted Property Appraiser's value, so my 50% threshold should be higher.  How do I validate this?

A: Obtain a private Market Value property appraisal from a local property appraisal company.  Typically, in this locality, a private appraisal usually shows buildings at significantly higher values.  With a private appraisal, the 50% threshold will be based upon the value of this building shown on the private appraisal; not the overall value of the property, just the building's value.  This is the property value minus... land, site improvements and values for other buildings on the lot.

On a private appraisal, the value of the building utilized is the labeled “Depreciated Cost of Improvements,” which is often found on page 3 of a six-page Uniform Residential Appraisal Report.

Submitting a private appraisal to the City doesn't affect your property tax rate.

Note: Whatever appraisal value you end up using, you'll have to keep using that value for the next five years. Because the percent of improvement is determined by the value of the building prior to improvements, you can't keep obtaining appraisals to include the new work you've done to increase the 50% threshold. 

Nor can you use one appraisal method at the beginning, and another later during this five-year window.


Q:  How is the value of improvements determined?

A:  The value of improvements is based upon a total of costs of improvements made to a building within the past five years.

Non-building related work for site improvements such a patios, driveways/pavers, pools/spas, irrigation, fences etc. aren't included.  For a list of costs that are included or exempt from Substantial Improvement calculations, please review the Substantial Improvement Brochure.

The cost of renovations or new construction is estimated as follows:

  • Residential:
    • $185sf w/o foundation modifications
    • $200sf with foundation modifications
      • (Includes vertical additions or new floors to an existing home.)

This rate is the same for owner-builders, volunteer labor or discounted materials, because FEMA requires the City apply the value of the work, rather than any discounted actual costs. For example, if a volunteer organization offered to construct a home at no cost it would still have the same value.

In some instances, permitted work that never received final inspections may be considered within the current fire-year period; unless it can be determined - to the Inspectors satisfaction - that the work had been completed more than five years ago.

If work to a building wasn't finished during any five-year period, this five-year window is extended until final inspections have been approved. In other words, this five-year clock doesn't reset upon uncompleted projects, simply because it took longer than five years to finish the work. 

Decks: If decks are attached to a building then these costs are included. If the deck is separated from the building - by a little as a fraction of an inch - then these costs are excluded from these calculations. FEMA considers that during flood conditions attached decks may toque loads upon an attached building; yet decks will break-away on their own when not so attached. 

Carports, Detached decks, Roofs, Sheds, Commercial, etc.: The City will still seek to determine reasonable cost estimates for these type improvements, as opposed to applying the square-foot costs.


Q:  Instead of elevating my home, can I dry floodproof it?

A:  Sorry...No. FEMA prohibits the use of floodproofing in lieu of elevation. Homeowners are free to employ floodproofing measures, but if elevation is required, floodproofing isn't an alternative.

There's no flood insurance discount for floodproofing a home, but there's major discounts for elevating one.

Q.  Does the 5-year rule reset with a change of ownership?

A:  No.  The 50%-Rule applies to buildings, irrespective of ownership.

Q:  Instead of elevating my commercial building, can I dry floodproof it?

A: Probably.  Commercial buildings may employ floodproofing in lieu of elevation.  UNLESS... the building has residential usage: motels, hotels, sleeping rooms for rent or lease, apartments, hospitals, medical facilities where patients are housed, and child or elder day care. Basically, where people work floodproofing is permittable; but where they live and sleep isn't. 

Floodproofing is prohibited in VE-type flood zones and Coastal A Zones.


Q:  How high does my building need to be elevated?

A: Every location within a regulated flood zone has a pre-determined flood level, known as the Base Flood Elevation (BFE).  In type "A" flood zones, the height of a building is measured to Finished First Floor, usually referred to as the first habitable floor.

For example, an "AE-6" flood zone indicates when a substantial flood event occurs, minimum flood levels at this location are expected to be six feet above sea level.  Current building codes require Substantially Improved buildings be elevated one-foot higher than the BFE (known as the Design Flood Elevation or DFE).  Therefore, a home within an "AE-6" flood zone would need to be elevated to at least seven-feet above sea level. (See Online Flood Maps)

Type "VE" flood zones are located along shorelines and have more stringent construction standards.  The appropriate flood level for these buildings is measured at the lowest horizontal cross-member. That underside of that cross-member must be one foot higher than the Base Flood Elevation for the specific site. Within Coastal A Zones, this higher standard is also required. 

If you're seeking a building permit under the Building Permit Allocation System (B-PAS), the minimum height requirement is 1.5-feet above BFE.


Q:  My lot is above sea level, so how high on the lot must I raise my house?

A: To know this, you'll need an Elevation Certificates, provided by a land surveyor.  That certificate, will record the height of the land above sea level, and the height of a building's first finished floor above sea level. Subtract the height of the land from required elevation of the home, and the result is how high the building must be elevated. 

For example:  A home in an AE-6 flood zone has an Elevation Certificate showing the grade is four feet above sea level. The building must be elevated seven feet (BFE +1'). 

Equation: [Required height (7')] - [Grade height (4')] = Height of elevated first floor above grade (3'). (See video explanation of Elevation & Freeboard)

Note: The standards are higher in VE & Coastal A flood zones, and buildings permitted under the Building Permit Allocation System BPAS.).


Q:  An Elevation Certificate shows my first floor is only 1/4" below the required elevation.  Isn't that close enough?

A: Unfortunately, no. FEMA doesn't allow any margin of error when it comes to building elevation requirements. However, since in "A" type flood zones, a building's height is measured at the Finished First Floor, you could build-up the floor with another layer of 1/2" plywood, or install floor tile and the building would then measure to the required height (carpeting and rugs don't count).


Q:  I want to substantially renovate my building.  An Elevation Certificate shows it's higher than the flood level (BFE), but lower than the building code requirement of flood-level-plus-one-foot. Do I still have to elevate it?

A: Yes.


Q:  My building has been officially designated a Historically Contributing Structure.  Am I still required to elevate it?

A: No. FEMA has exempted such structures from the elevation requirements related to Substantial Improvement.  UNLESS... anything is done to the structure that would affect its status as a contributing historic structure.  Note: Utilities and machinery are still required to be elevated to proper flood levels.  HOWEVER... your building won't be exempt from very high flood insurance costs, depending upon the depth of the building below the flood level.

Note: There's a major difference between "Historic Structures" & "Contributing Historic Structures."  Only the latter are exempt from elevation/floodproofing requirements.

A "Historic Structure" may be any building older than 50 years. Whereas a "Contributing Historic Structure" is a documented building on the state list of historic structures; this list is maintained by the local HARC board. 


Q:   What are some examples of the ways in which structures can be substantially improved?

A:  Generally, structures are substantially improved in one of five ways:

  1. Rehabilitations - improvements made to an existing structure which do not affect the external dimensions of the structure;
  2. Additions - improvements that increase the square footage of a structure. Commonly this includes the structural attachment of a bedroom, kitchen, den, recreational room, or other type of addition to an existing structure;
  3. Reconstructions - cases where an entire structure is destroyed by damage or is purposefully demolished or razed and a new structure is built on the old foundation or slab;
  4. Substantial Damage - structures that are considered substantial improvements when they incur substantial damage, meaning repairs will cost 50% or more of the building's value. Substantial improvement more commonly occurs in non-disaster everyday situations through the rehabilitation of, or addition to structures. Substantial damage occurs during storm events, a fire or severe neglect/deterioration. 
  5. Adding another inhabitable building on the same lot, can trigger requirements that the existing building be elevated as well.  Unless, the new building is a legal Independent Living Unit. 


Q:  What is a Substantially Damaged Structure?

A:  As defined in 59.1 of the NFIP regulations, a building is considered to be substantially damaged when: "damage of any origin is sustained by a structure whereby the cost of restoring the structure to its before damaged condition would equal or exceed 50 percent of the market value of the structure before the damage occurred."  Buildings can also be declared Substantially Damaged due to neglect or excessive deterioration. Such buildings can't be renovated nor repaired without elevation.


Q.  What the difference between Substantial Improvement & Substantial Damage?

A.  Substantial Improvement can occur gradually during five years or less, when repairs/renovations/additions total 50% of the building's value. Substantial Damage usually occurs during severe storm events, a fire or severe neglect/deterioration. Once so declared, a Substantially Damaged building can't be repaired without meeting current flood damage prevention requirements (usually elevation).


Q:  In terms of NFIP regulations, if a structure is determined to be substantially damaged, what must happen to that structure?

A:  All structures that are determined to be substantially damaged are automatically considered to be substantial improvements, regardless of the actual repair work performed. In other words, if the cost necessary to fully repair the structure to its before damaged condition is equal to or greater than 50% of that structure's market value before damages, then the structure must be elevated (or floodproofed if it's non-residential) to or above the level of the design flood elevation, and meet other applicable program requirements.


Q.  There are multiple buildings on one lot, that I want to build/renovate.  Why am I being asked to file a building permit application for each one separately?

A.  Different buildings often have different building standards that require different inspections types.  Additionally, the value of improvements needs to be tracked individually by building.  

This better assists the Applicant as well, in that buildings can be brought online as inspected and approved, whereas lumping all buildings into a single application would tie the status of all to the final inspection of the very last piece of the overall project.

If the plans encompass multiple buildings, then only one set needs to be submitted (not duplicate sets for each application.)

Q:  I recently renovated my building to 49% of its market value, then a fire damaged one room. It's going to cost more than 1% of the building's value to make repairs. Must I now elevate the building?


Q:  A couple of years ago I renovated my home to 42% of its value.  Now a hurricane unexpectedly damaged the roof, and it'll cost about 10% of the building's value to repair.  Does the building need to be elevated just because I now need to repair the roof?

A: The answer to both questions is "Yes." Once the 50% threshold is reached - for any reason - elevation is required.


Q.  I have a shed (or garage) in the back yard, that I want to convert to a bedroom (or other living space).  Does it have to be elevated?

A.  Yes, for a couple of reasons.  

  1. As a shed or garage, it was permitted to be below flood levels so long as it had flood vents in the bottom.  As such, it could only be used for storage and parking. Converting this storage space to habitable space (occupied room, office, workshop etc) is a change of use, which requires elevation.
  2. This conversion will most likely exceed 50% of the building's value, resulting in a Substantial Improvement, which requires elevation. 


Q. The second floor of my building is well above the flood level.  Are repairs to this portion of the building included in the Substantial Improvement calculations?

A. Yes. If the base of the building is below the flood level, all improvements to the building are included, no matter where on the building they occur. 


Q: How high does a mobile home need to be elevated?

A: New and Substantially Improved Mobile homes within a mobile home park need to be elevated so that the bottom of the frame reaches or exceeds the Base Flood Elevation for that site.

  • Mobile homes placed or moved anywhere within the city must be elevated to Base Flood Elevation to the bottom of its frame.
  • Mobile homes aren't permitted in type "V" or "Coastal A" flood zones.


Q.  If a building's construction was permitted before the flood map date, but finished after that date, what rules apply?

A:  The date the project was permitted is the controlling date.  When trying to determine which flood maps standard would have applied when a building was constructed, look for the date the construction was approved and permitted.  Compare that date against the effective dates of the flood maps in effect at that time. The most recent flood maps prior to the date of permitting apply. 


Q. Does solar equipment count toward the 50%?

A. Yes. While in Florida solar equiptment may be exempt from increasing property taxes, FEMA still considers such a building improvement.

Q. Additions (residential)

If the cost of constructing an addition is less than 50% of the main structure's value, then only the addition needs to be elevated. (FBC 1101.1)

If the cost of the addition - along with any renovations to the main building - is more than 50%, then both the addition and the existing building require elevation. [Exception: Buildings that have legal additional living units, stand on their own merits.]

Buildings with non-residential uses have an option to floodproof, and the same senarios apply. 

Link to exerpt of Florida Building Code concerning such additions.


Contact Us

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