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Flood Rules
Substantial Damage & Substantial Improvement

Notice To All Property Owners 
Making additions or alterations to a structure whose lowest floor is below the base flood elevation or rebuilding your home or structure after the storm?

If your residential or non-residential structure is located in a Special Flood Hazard Area (SFHA) and is below the Base Flood Elevation (BFE), the City of Naples has flood damage prevention regulations that may affect how you remodel, renovate, or add on to your building. If your building has sustained structural and/or interior damage, these regulations may affect how it is reconstructed. Communities that participate in the National Flood Insurance Program (NFIP) are required to adopt and enforce laws in accordance with 44CFR Sections 59.1 and 60.3. Federally backed flood insurance is available for residents and property owners of communities in good standing with the NFIP.

SUBSTANTIAL DAMAGE means damage of any origin sustained by a structure whereby the cost of restoring the structure to its pre-damaged condition would equal or exceed 50% of the market value or replacement cost of the structure before the damage occurred. (Note: The cost of the repairs must include all costs necessary to fully repair the structure to its before damaged condition).

SUBSTANTIAL IMPROVEMENT means any reconstruction, rehabilitation, addition, or other improvement of a structure, the cost of which equals or exceeds 50% of the market value of the structure before the “start of construction” of the improvement. If a building is “substantially damaged” or “substantially improved”, it must be brought into compliance with the City of Naples flood damage prevention regulations, including elevating the building to or above the base flood elevation. In accordance with the National Flood Insurance Program and the Federal Emergency Management Agency the City of Naples shall determine “substantial damage” and “substantial improvement” and has implemented the following procedures to do so:

The City will use the assessed value of your structure recorded by the Collier County Property Appraiser’s Office. This value excludes the land, pool/spa, and any item not a permanent part of the structure. (Please contact the County Property Appraiser’s office or the City’s Building Department to obtain this value). However, if you disagree with the Property Appraiser’s valuation of the structure, you may engage a State of Florida licensed property appraiser to submit an appraisal for the Depreciated Replacement Cost (Actual Cash Value) of the structure. This appraisal must be dated no later than (6) months from the date of permit submittal.

You must obtain and submit a detailed and complete cost estimate to the City of Naples for the addition, remodeling, reconstruction or for repair of all the damages sustained by your structure. The cost estimate must be prepared and signed by a licensed contractor. In addition, the contractor must sign an affidavit indicating that the cost estimate includes all damages or all improvements to the structure, not just structural. A signed contract must be submitted with the permit application. If the owner is the contractor, the owner is responsible for submitting the cost estimate, and providing documentation, including subcontractor bids.

The City will evaluate the cost of improvements or repairs and determine if they are fair and reasonable. For damage repairs, pre-storm prices and rates will be utilized. The cost of improvements or repairs does not include items not considered a permanent part of the structure (i.e. plans, surveys, permits, sidewalks, pools, screens, sheds, gazebos, fences, etc.).

If a structure is determined to have “substantial damage” or is proposed to be “substantially improved”, then an Elevation Certificate must be submitted to the City of Naples to determine the lowest floor elevation. Also, building plans must be submitted illustrating how the structure will be elevated. Please note that garages and carports are not considered to be the “lowest floor” as long as they are used solely for parking of vehicles, building access and storage. If the lowest floor and all electrical, plumbing, and mechanical equipment are above BFE, the building can be repaired and reconstructed without having to comply with the 50% Rule.

The NFIP allows a new or substantially improved non-residential building in Zone AE to have its lowest floor below BFE provided that the building has been designed, constructed, and certified to be floodproofed. Floodproofing of areas below the BFE in residential buildings is not permitted under the NFIP nor is floodproofing permitted in a Coastal High Hazard Area (Zone VE). The City of Naples requires submittal of a Floodproofing Certificate for every floodproofed building within a Special Flood Hazard Area (SFHA) before obtaining a Certificate of Occupancy or Completion.

Following a presidential disaster declaration, the Small Business Administration (SBA) may make loans available for both residential and non-residential buildings for purposes of elevating the structure to or above the base flood elevation. Proof of “substantial damage” from the City of Naples is required for loan processing.

Donated or Discounted Materials:
The value placed on materials must equal the actual or estimated cost of all materials to be used. When materials or servicing equipment are donated or discounted below normal market values, the value must be adjusted to an amount equivalent to that estimated through normal market transaction.

Self or Volunteer Labor:
The value placed on materials must be equal to the actual or estimated labor charge for repairs of all damages sustained by the structure. Where non-reimbursed (volunteer) labor is involved, the value of the labor must be estimated based on applicable minimum hourly wage scales for the type of construction work to be completed. The building official, based on his professional judgment and knowledge of local and regional wage scales can provide additional guidance to determine reasonable labor rates for professional trades (i.e. electricians, plumbers, block masons, framing, HVAC, etc.)

Interpretations To The Rules

Below are a list of documents that might help when trying to navigate the world of "Flood Rules" and what you can or can't do as a property owner when it comes to living or working in a special flood hazard area.

Lowest Floor Below Base Flood Elevation

Market Value


Removing A Roof of A Non-Compliant Structure

Dehumidification of Lowest Floor Below Base Flood Elevation 

Frequently Asked Questions Regarding the 50% Rule