Florida Keys
Home Addition in Monroe County, Florida
Permit requirements, inspections and modeled costs for home addition in unincorporated Monroe County. If your address falls inside a city, the municipal building department issues the permit instead.
Verified August 2026
Do you need a permit for home addition in Monroe County?
Yes
Yes — a permit is required for home addition in Unincorporated Monroe County, FL. The work must be inspected before it can be closed out, and a licensed contractor generally has to pull the permit.
Budget $59,400 – $369,600 for the work itself (typically $138,600) plus $1,025–$7,680 in permit fees.
Monroe County cost model
| Budget scope | $59,400 |
|---|---|
| Typical project | $138,600 |
| Premium / complex | $369,600 |
| per sq ft of added space | $250 – $600 |
| Permit fees | $1,025 – $7,680 |
| vs national baseline | +32% |
| Timeline | 3-6 months of construction, 6-14 months including design and permitting |
Inspections you should expect
- Foundation / slab inspection
- Framing and sheathing
- Electrical, plumbing and mechanical rough
- Insulation and energy
- Final building inspection
What the county will ask for
- Building permit application
- Sealed architectural and structural drawings
- Site plan and survey showing setbacks
- Energy code compliance forms
- Notice of Commencement recorded with the county
- Contractor license and insurance
Cities inside the county that permit their own work
If the property is inside these municipalities, apply to the city rather than the county.
We track 5 municipalities in Monroe County: Key West, Marathon, Islamorada, Key Colony Beach, Layton. Contact the city directly if your address is inside one of them.
Statewide rules that apply here
Monroe County enforces the 8th Edition (2023) Florida Building Code, effective December 31, 2023. Local amendments can add requirements but cannot reduce the statewide minimum.
Frequently asked questions
How long does an addition permit take in Florida?
Plan review for an addition typically runs four to twelve weeks depending on the jurisdiction, and that is after the sealed drawings are complete. Coastal and flood-zone properties take longer because of elevation review.
Do impact fees apply to a home addition?
Many Florida counties assess impact fees on added conditioned square footage. The fee is usually calculated per square foot and can add thousands to a large addition, so ask for the fee estimate before design.
Sources
Sources & verification
Last verified August 2026. Cost figures are modeled estimates based on national baselines adjusted for local labor and material pricing — they are not quotes. Permit rules change; confirm with the building department before starting work.