Monroe County, FL: flood zone, zoning and property lines by address
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Towns in Monroe County: Key Largo, Marathon, Islamorada.
Flood zone by address
ParcelSheet reads FEMA's National Flood Hazard Layer at the lot: the zone, whether it is a high risk area where lenders ask for flood insurance, and the base flood elevation where FEMA lists one. FEMA's countywide study for Monroe County has 183 FIRM panels, the newest effective February 2005; coastal V zones, where waves add to the flood, are mapped along its shore.
The official panel and any Letter of Map Amendment are at FEMA's Map Service Center. An elevation certificate for a Monroe house comes from a licensed surveyor and is often on file with the county or city building office (Building and Permitting).
Property lines
The parcel outline, parcel number and mapped size come from the Florida statewide cadastral (county property appraiser parcels with the Department of Revenue tax roll), so a Monroe lot shows the same lines the property appraiser draws. Monroe County covers about 629,148 acres of land and 2,756,174 acres of water.
Mapped lines are approximate. The Monroe County Property Appraiser keeps the parcel record; a licensed surveyor sets the true corners.
An example from the county's own records: parcel 0666 33 00333140000000 in Marathon, a lot with one house, about 3,666 square feet as mapped, the house built in 2023. Open it to see every card ParcelSheet draws for a Monroe lot.
Zoning
Monroe County zones its unincorporated land, and Marathon zones the land inside its limits. ParcelSheet shows the use the property appraiser lists for the lot and links Planning and Environmental Resources for the district, the uses it allows and the lot size it needs.
ADU and guest houses
Florida Statute 163.31771 lets local governments allow an accessory dwelling unit on a lot with a house. Whether a Monroe lot can add one depends on its district; Planning and Environmental Resources has the rule. ParcelSheet shows the mapped lot size and the ground's slope, the first two things the question turns on.
Septic and soil
ParcelSheet reads the USDA soil survey at the lot: the soil's name, its septic absorption rating and whether it is prime farmland. Monroe County is soil survey area FL687, Monroe County, Keys Area, Florida, last updated August 2026, on Web Soil Survey.
A new or changed septic system in Monroe County needs a permit from the Florida Department of Health in Monroe County, which tests the soil on the lot itself.
Setbacks
Setbacks in Monroe County come from the zoning district: the front, side and rear distances a house must keep. ParcelSheet does not draw setback lines; Planning and Environmental Resources gives them for the lot's district, and Marathon for land inside its limits. On the Monroe shore, building seaward of the state's Coastal Construction Control Line needs a state permit.
Hazards that apply
- Sinkholes. The Florida Geological Survey lists 1 subsidence incident report in Monroe County (the reports). They are reports, not confirmed sinkholes; ParcelSheet does not rate a lot for sinkholes.
- Storm surge. Monroe County has coastal V zones on its FEMA map, so storm surge reaches its shore. The county's evacuation zones are on its emergency management site; ParcelSheet shows the FEMA zone and the 3 ft sea level rise map at the lot.
- Wind. The Florida Building Code sets the design wind speed for a house in Monroe County; the building office (Building and Permitting) applies it at permit.
- Wetlands and wildfire. ParcelSheet shows the National Wetlands Inventory near a Monroe lot and the Forest Service wildfire hazard rating at it.
Questions
Is my house in a flood zone in Monroe County?
Type the address in the box above and ParcelSheet reads FEMA's flood zone at the lot's center. FEMA's countywide flood map for Monroe County has 183 panels, the newest effective February 2005. A lender or insurer uses the official FIRM panel; FEMA's Map Service Center has it.
How do I find property lines in Monroe County?
Open the Florida map, type the address, and the parcel outline from the county property appraiser shows on the map with its parcel number and mapped size. The Monroe County property appraiser keeps the official record. Mapped lines are approximate; only a licensed surveyor sets the true corners.
What is my property zoned in Monroe County?
Zoning in Monroe County is set by the county for unincorporated land and by each city (such as Marathon) inside its own limits. ParcelSheet shows the use code the property appraiser lists and links the office that sets the zoning; the planning office has the final word.
Can I build an ADU in Monroe County?
Florida Statute 163.31771 lets counties and cities allow an accessory dwelling unit, and each sets its own rules. In Monroe County ask the zoning office for the lot's district first; ParcelSheet shows the lot size as mapped so you can see the room you have.
Do I need a septic permit in Monroe County?
Yes. A new or changed septic system in Monroe County needs a permit from the Florida Department of Health in Monroe County. ParcelSheet shows the USDA soil survey's septic rating at the lot, from survey area FL687 (Monroe County, Keys Area, Florida).
Next to Monroe County: Collier County, Miami-Dade County.
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