Free tool

Substantial damage calculator: is your house over the 49% or 50% line?

Divide the cost to repair the building by what the building alone (not the land) was worth before the damage. In St. Petersburg and in the parts of Pinellas and Pasco counties outside city limits, 49% or more is substantial damage. In Hillsborough County outside city limits, and in Tampa, Clearwater and New Port Richey, the line is 50%. This tool does the math with your local number. Your local floodplain manager makes the final call.

By Matan, owner of Tao Home Buyers. Last reviewed October 30, 2026. General information, not legal or tax advice.

Your estimate

Enter the building value and the repair cost to see the share.

What crossing the line means

If the building is in a high-risk flood zone and the local office finds it substantially damaged, the whole building has to meet today's flood rules, not just the damaged parts. For most houses that means raising the house, or tearing it down and building new.

If you have a flood policy through the National Flood Insurance Program, its Increased Cost of Compliance coverage may pay up to $30,000 toward raising, moving, floodproofing or tearing down the building. Confirm with your insurer and on FEMA's ICC page.

An estimate only. Your local floodplain manager or building official makes the decision, not FEMA, your insurer or this tool. Selling the house does not change a determination (FEMA P-758). Thinking about selling as-is? Tell us about the house.

How does the substantial damage math work?

Cost to repair. The full cost to restore the building to how it was before the damage, including materials and labor. Pinellas County says your own labor and donated materials count, priced at normal commercial rates.
Building value. The structure only, before the damage. Land does not count. Offices use an independent appraisal of the building's actual cash value, or the Property Appraiser's building value adjusted to market.
Divide the first by the second. The local codes say "equal or exceed," so a result exactly on the line counts as substantial damage.

Example: a building worth $200,000 before the damage

An example only, land not counted
Repair cost	Share of building value	Where the line is 49%	Where the line is 50%
$90,000	45.0%	Under the line	Under the line
$98,000	49.0%	Substantial damage	Under the line
$99,000	49.5%	Substantial damage	Under the line
$110,000	55.0%	Substantial damage	Substantial damage

Pasco County's own example. The county's flyer starts from the Property Appraiser's building Just Value of $200,000, adds 15% to get a market value of $230,000, then multiplies by 0.49: $112,700. Repairs below that, hire a contractor and pull permits. Repairs at or above it, call Pasco Building Construction Services at 727-847-8126.

Why do some places use 49% instead of 50%?

The federal rule is a minimum. FEMA says a community can adopt a stricter standard, giving 45% of market value as an example, and then the community's number applies. Pinellas County, St. Petersburg and Pasco County wrote 49% into their own rules. St. Petersburg says following its flood rules keeps the city eligible for federal flood insurance, FEMA disaster help and FEMA grants, and protects the 25% flood insurance discount the whole community gets.

One point sounds small, but it moves the line. On a $200,000 building, the 49% line is $98,000 of repairs and the 50% line is $100,000.

Each line read on the official page on October 30, 2026
Where the house is	Line	Official page
Pinellas County (outside city limits)	49%	Pinellas County Code Sec. 158-182 (Municode)
City of St. Petersburg	49%	St. Petersburg City Code Sec. 16.40.050.9.4 (Municode)
City of Clearwater	50%	Clearwater Community Development Code Sec. 51.851 (Municode)
Hillsborough County (outside city limits)	50%	Hillsborough County: Substantial Damage/Improvement Guidelines
City of Tampa	50%	Tampa City Code Sec. 5-121.182 (Municode)
Pasco County (outside city limits)	49%	Pasco County flyer: Repairing Homes in a Flood Zone (PDF)
City of New Port Richey	50%	New Port Richey: Flood Risk

Any other city sets its own number. Ask that city's floodplain manager or building department which one applies to the house.

What does the result mean, and what doesn't it mean?

It is an estimate. Only your city or county's building official or floodplain administrator decides. FEMA says that it and your insurance company do not make substantial damage determinations.
Damage from any cause counts. The codes say damage "of any origin," so wind and fire damage count, not only flood.
It matters most in high-risk flood zones. FEMA describes substantial damage assessments in the Special Flood Hazard Area, the high-risk zones on the federal flood map.
The office may use different numbers. A detailed repair estimate or an appraisal of the building can change the result. Pasco County's flyer also warns that improvements made in the past year could affect the math, so ask how your office counts recent work.
A sale does not change it. FEMA's desk reference for local officials (FEMA P-758) says a change of ownership has no bearing on the determination. It is based on the building's value before the damage, whether it is made before or after a sale.

What are your options if the house is over the line?

Repair and bring the whole building up to code. Over the line, the damaged parts can't simply be fixed. The whole building has to meet current flood rules. For most houses that means raising the house.
Raise (elevate) the house. If you have a flood policy through the National Flood Insurance Program, its Increased Cost of Compliance coverage may pay up to $30,000 toward raising, moving, floodproofing or tearing down the building. Confirm with your insurer. Few owners have used it yet; see our Tampa Bay flood numbers.
Tear it down and rebuild to current flood rules.
Ask for a reassessment or appeal. If you think the office used the wrong repair cost or building value, bring a detailed estimate or an independent appraisal. Pasco County says, "If you disagree with the determination, you may request a re-assessment."
Sell the house as-is. The determination stays with the building, so any buyer has to deal with the same rules. A cash offer for a house like this prices in that work and is usually well below what a repaired house would sell for. Compare it with the cost of the other options before you decide.

For the letters, deadlines and help programs in each county, read our guide to the FEMA 50% rule in Tampa Bay. If you are weighing a sale, see selling a house with flood or hurricane damage.

Sources

Each page was opened on October 30, 2026.

FAQ

Questions about the 50% and 49% rules

How do you calculate the FEMA 50% rule?

Divide the cost to repair the building to its condition before the damage by the market value of the building alone (not the land) before the damage. If the result equals or exceeds the local line, which is 50% under the federal rule and 49% in some places, the building is substantially damaged.

Is St. Petersburg's substantial damage rule 49% or 50%?

49%. St. Petersburg's city code (Sec. 16.40.050.9.4) counts a building as substantially damaged when repairs would equal or exceed 49 percent of its market value before the damage. We checked the code on October 30, 2026.

What is the substantial damage threshold in Pinellas County?

49% for houses outside city limits, under Pinellas County Code Sec. 158-182. Each city sets its own number. St. Petersburg uses 49%. Clearwater's code says 50%, but a glossary page on the city's website still says 49%, so confirm with the city.

Does Pasco County use 49% or 50%?

Pasco County uses 49% outside city limits. Its flyer adds 15% to the Property Appraiser's building Just Value to get market value: $200,000 becomes $230,000, and 49% of that is $112,700. The City of New Port Richey uses 50%.

Do Hillsborough County and Tampa use the 50% rule?

Yes, both use 50%. Tampa's code adds a second test: flood damage on two separate occasions within ten years also counts when the repairs each time average 25% or more of the building's value.

Who decides whether my house is substantially damaged?

Your city or county's building official or floodplain administrator. FEMA says that it and your insurance company do not make substantial damage determinations. This calculator only gives you an estimate.

What building value should I use?

The building only, as it was before the damage, not the land. Offices here use an independent appraisal of the building's actual cash value or the Property Appraiser's building value adjusted to market. Pasco County's flyer adds 15% to the Property Appraiser's building Just Value.

Does selling the house change a substantial damage determination?

No. FEMA's desk reference for local officials (FEMA P-758, section 5.6.5) says a change of ownership has no bearing on the determination, which is based on the building's value before the damage, whether it is made before or after the sale.

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We buy houses in Pinellas, Hillsborough and Pasco counties, including St. Petersburg, Clearwater, Largo, Tampa, Brandon, Plant City, New Port Richey, Wesley Chapel and Zephyrhills.

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Matan is a licensed Florida real estate sales associate with Jay Alan Real Estate, buying for his own company.