Updated November 4, 2026
What the rule is
Communities that take part in the National Flood Insurance Program must regulate building in flood hazard areas. FEMA's fact sheet says a structure in a Special Flood Hazard Area is substantially damaged when the total cost of repairs is 50 percent or more of the structure's market value before the disaster. Communities may set a stricter standard, but not a weaker one.
The cause of the damage does not matter for the rule. A local official, such as the building official or floodplain manager, makes the determination. FEMA does not make it or notify owners.
A note on the number: Pinellas County's own page describes its threshold as repair costs of 49 percent or more of the home's value without the land. Always check the figure that your own city or the County applies.
A simple example
FEMA's example: a structure worth $200,000 (land excluded) that needs $120,000 in repairs is substantially damaged. The comparison is repair cost divided by pre-damage market value of the building only.
What counts as cost
According to Pinellas County, the cost side includes materials and labor (even donated materials and owner or volunteer labor, estimated at market rates), structural elements, demolition and debris disposal, contractor overhead and profit, utility equipment, finishes, site preparation, elevation or floodproofing, and the cost of meeting code requirements. Doing the work yourself does not lower the figure.
How the home's value is set
Pinellas County says market value can be shown with a retrospective actual cash value appraisal by a qualified independent appraiser, or by the Property Appraiser's just value of the structure, adjusted to approximate market value. You can look up your property at pcpao.gov. If that value looks too low, the County says you can request a free pre-storm Building Value Reconsideration or pay for an independent appraisal, and then apply for a reassessment.
If your home is substantially damaged
The structure must be brought into compliance with local floodplain management rules. FEMA says owners may elevate or otherwise modify the structure, relocate or demolish it. Pinellas County says homes must be elevated or rebuilt to current floodplain codes if repairs aren't compliant.
If you carry NFIP flood insurance with Increased Cost of Compliance (ICC) coverage and the building is substantially damaged by flooding in a Special Flood Hazard Area, FEMA says eligible policyholders may receive up to $30,000 toward elevation, relocation or demolition. Ask your insurer how it applies to you.
Permits: do not start without one
Pinellas County warns that you should not start repairs without a permit, or you may have to undo the work at your own expense. All permits are reviewed for substantial damage and substantial improvement compliance. For minor damage (under 12 inches of water and below power outlets), the County says to apply for permits. For extensive damage, hire a licensed contractor or submit photos and a detailed repair estimate.
The County handles unincorporated areas only. If you live in a city such as St. Petersburg, Clearwater or Largo, ask your city's building department. Pinellas County's Building and Development Review Services can be reached at (727) 464-3888, and Floodplain Management at (727) 464-7700.
If you disagree with the result
The County describes a reassessment process: if the determination doesn't change after review, you can accept it and elevate or rebuild, or appeal. If the reassessment changes the result so repairs fall below the threshold, you can repair, with plans and estimates submitted. Instructions are posted on the County's substantial damage page at pinellas.gov. Cities have their own steps, so ask yours.
What to do right now
Photograph the damage, keep every estimate and invoice, and ask your city or the County whether a substantial damage review applies to your home before you hire a contractor. Pinellas County also offers a Substantial Improvement Disclosure form and a FEMA cost breakdown worksheet on its page. Contact the County's substantial damage inspection team at sdinspection@pinellas.gov with questions if you are in an unincorporated area.
The same rule can apply to remodels, not only storm damage. Pinellas County's flood guide specifically suggests checking whether a remodel triggers the 50 percent rule before you plan one.
Frequently asked questions
Does the rule apply to every home?
FEMA's definition applies to structures in Special Flood Hazard Areas. Communities may set stricter standards, so check with your local building department.
Does my own labor count?
Per Pinellas County, owner and volunteer labor and donated materials are counted at market rates.
Is the land included in the value?
No. Market value is for the building, excluding land.
Who decides if my home is substantially damaged?
A local official, such as your building official or floodplain manager, not FEMA.