People call it the FEMA 50% rule because it comes from the National Flood Insurance Program, but your city or county enforces it through its floodplain rules and the Florida Building Code. It only applies in flood hazard areas, and it only looks at the building, not the lot. Here's how it works, what counts, and what your options are when you're near the line.
The basics
What the 50% rule is
Substantial improvement
A renovation, addition or other improvement whose cost equals or exceeds 50 percent of the building's market value before the work starts.
Substantial damage
Damage from any cause, like a flood, a hurricane or a fire, where restoring the building to its condition before the damage would cost 50 percent or more of its market value before the damage.
Only in flood hazard areas
The rule applies to buildings in a special flood hazard area on the FEMA flood map, in communities that take part in the National Flood Insurance Program. That includes large parts of coastal Miami-Dade, Broward and Palm Beach.
The building, not the land
The comparison is the cost of the work against the value of the structure alone. The land, the pool, the driveway and other site improvements aren't part of the market value.
The math
How the 50% is calculated
Find the building's market value
Usually the building-only value from the county property appraiser, sometimes adjusted by a factor the property appraiser provides, or a licensed appraiser's valuation of the structure alone. It's the value before the work or before the damage.
Price the full scope of work
Use a complete, realistic estimate for everything you plan to do to the building, including labor, materials, overhead and profit. Donated materials and your own labor are counted at market rates.
Divide the cost by the value
If the cost of the work is half the building's value or more, it's a substantial improvement or substantial damage. Under half, the work can generally go ahead without bringing the whole building up to current flood rules.
The building official decides
You or your contractor submit the numbers, and the building department's floodplain administrator makes the determination. They can question an estimate that looks too low or ask for another appraisal.
What counts
What goes into the cost, and what's left out
Communities follow FEMA's guidance on this, with some local differences. These are the typical lists.
Usually counts toward the 50%
- Structural work: foundations, slabs, walls, roof framing and roofing
- Windows, doors and exterior finishes like stucco and paint
- Interior walls, drywall, flooring over the subfloor, cabinets and built-ins
- Kitchen and bath fixtures and built-in appliances
- Electrical, plumbing, HVAC and ductwork
- Attached decks and porches
- Labor to tear out or alter parts of the building as part of the work
- Contractor overhead and profit, plus donated materials and owner labor at market value
Usually left out
- Plans, specifications, surveys and permit fees
- Debris removal and cleanup after a storm, like dumpsters, hauling and drying out
- Furniture, rugs and appliances that aren't built in
- Pools, screen enclosures, fences, driveways, sidewalks and landscaping
- Sheds, gazebos and detached garages
What changed in 2025
Florida banned lookback periods
What a lookback was
Many cities used to add up all your permits over a set period, often one to five years, and apply the 50% test to the total. Two modest projects a year apart could cross the line together.
The new law
SB 180, signed June 26, 2025, created section 163.31795 of the Florida Statutes. It says a local government in the flood insurance program may not adopt or enforce a substantial improvement ordinance that includes a cumulative period. The 2026 session didn't change it.
Some city pages haven't caught up
You may still find city web pages and policies that describe a one or two year lookback. Ask your building department how it applies the rule today before you plan around an old page.
One project is still one project
Building officials look at the full scope of the work you're planning. Splitting a single renovation into smaller permits isn't a reliable way around the rule.
Crossing the line
What happens if you hit 50%
The whole building has to comply
Not just the part you're working on. A substantially improved or damaged building generally has to meet the floodplain rules for new construction.
Raising the lowest floor
Under the Florida Building Code, the lowest floor in a flood hazard area generally has to be at or above the base flood elevation plus one foot. Some cities require more.
Equipment and the space below
Electrical and mechanical equipment goes above the flood level, and the area below it is generally limited to parking, access and limited storage, built with flood resistant materials.
Commercial buildings have one more option
Nonresidential buildings can sometimes be dry floodproofed instead of elevated. Homes generally can't.
Your options
Stay under, elevate or tear down
| Item | When it fits | What to watch |
|---|---|---|
| Keep the work under 50% | The house is sound and a smaller scope gets you most of what you want | The estimate has to be complete and realistic. A low number that doesn't hold up can stop the permit |
| Elevate the existing house | The structure is solid and worth keeping | Lifting a slab-on-grade concrete block house is a big structural job, and the house still has to meet current rules |
| Tear down and build new | The house is older, the bones are weak, or elevating costs close to building new | The new house is new construction, so it's designed to today's flood, wind and setback rules from the start |
Many owners in flood zones end up comparing the second and third rows. Get the elevation, the remodel and the demolition priced before you decide.
After a flood
Flood insurance can help pay to comply
Increased Cost of Compliance
If you have a National Flood Insurance Program policy and the building is declared substantially damaged by a flood, ICC coverage can pay up to $30,000 toward elevating, relocating or demolishing it, or floodproofing a nonresidential building.
File before you repair
FEMA advises not to start repairs before filing an ICC claim. Talk to your flood adjuster and your building department first.
Storm damage and demolition
Our guide covers what happens after a storm, from unsafe structure notices to clearing the lot.
Before you plan
Three things to check first
Your flood zone
Look up the property on the FEMA flood map or your county's flood zone viewer. If it's not in a special flood hazard area, the 50% rule generally doesn't apply.
The building value
Find the building-only value on the Miami-Dade, Broward or Palm Beach property appraiser's site. That's usually the starting point for the math.
Your elevation
An elevation certificate shows how high the lowest floor sits compared to the base flood elevation, which tells you how far the house would have to go up.
Related
Keep reading
Common questions
Frequently asked questions
What is the 50% rule in Florida?
In a flood hazard area, if the cost to improve or repair a building equals or exceeds 50 percent of the building's market value, it's a substantial improvement or substantial damage. The building then generally has to meet current floodplain rules, which usually means elevating the lowest floor.
Does the 50% rule apply if I'm not in a flood zone?
Generally no. It applies to buildings in a special flood hazard area on the FEMA flood map. Check your property on the flood map or with your building department.
Does land value count in the 50% rule?
No. Only the value of the building counts. The land and site improvements like pools, driveways and fences aren't part of the market value.
Do Florida cities still use a lookback period?
Not legally, since June 2025. Section 163.31795 of the Florida Statutes bars local governments in the flood insurance program from adopting or enforcing a cumulative substantial improvement period. Some city web pages still describe the old rules, so confirm with your building department.
Can I split my renovation into phases to stay under 50%?
Not reliably. Building officials look at the full scope of the work you're planning, and FEMA guidance says a phased repair is judged on the cost of the whole job.
Does the 50% rule apply if I tear the house down and rebuild?
A new house is new construction, so it has to meet current flood rules from the start. The 50% test is for deciding whether work on an existing building triggers those rules.
Will flood insurance pay for demolition?
If you have a National Flood Insurance Program policy and your building is declared substantially damaged by a flood, Increased Cost of Compliance coverage can pay up to $30,000 toward elevating, relocating or demolishing it.
Is the 50% rule the same as the 25% roof rule?
No. The 25% roof rule is a separate Florida Building Code rule about roof repairs. Since 2022, if your roof was built to the 2007 Florida Building Code or later, only the damaged part has to be brought up to current code. The 50% rule is about flood zones and the whole building.
This article is general information, not legal advice. How the 50% rule is applied depends on your community's floodplain rules and the building official's determination, and the rules change. Confirm with your building department before you plan a renovation or a demolition.