Florida’s 25% rule comes from the Florida Building Code and applies to window and door replacements.
If a property owner replaces more than 25% of the windows on a building within a single 12-month period, the remaining windows may need to be upgraded to meet current code requirements, including impact resistance standards in wind-borne debris regions.
This often means adding hurricane-rated glass, shutters, or other protective measures on the untouched windows too, not just the ones being replaced. The rule exists to gradually bring older buildings into compliance with modern hurricane safety standards.
Homeowners planning partial window replacements should check with their local building department, since enforcement can vary by county or municipality.