The 50% Rule is a regulation of the National Flood Insurance Program (NFIP) that prohibits improvements to a structure exceeding 50% of its market value unless the entire structure is brought into full compliance with current flood regulations. This may include elevating the structure, using flood resistant materials, and proper flood venting among others.

Damaged Property Repair and Rebuilding Rules within the Special Flood Hazard Areas:

• Hillsborough County Zone lookup
• FEMA Flood Maps and Zones Explained
• FEMA Substantial Damage Estimator Tool
• FEMA Damage Quick Guide
• Answers to Questions About Substantially Improved/ Substantially Damaged Buildings
• Frequently Asked Questions about FEMA's "50% Rule"
• Please check with your municipalities' building department for questions regarding:
  • FEMA 50% Rule Substantial Damage (SD) and Substantial Improvement (SI) Determinations
  • Permitting
  • Cumulative look-back periods that may affect SD/SI determinations
  • Elevation requirements to meet current code
  • Grandfathering of non-conforming uses