Do You Need a Permit to Build an ADU in Florida?

Building an accessory dwelling unit (ADU) in Florida always requires a building permit — and usually several more. ADUs, also called in-law suites, granny flats, casitas, or backyard cottages, are subject to the full Florida Building Code just like any new home. What's changed in 2026 is who gets to decide whether you can build one: Florida SB-48, effective July 1, 2026, now requires every municipality in the state to allow ADUs in single-family residential zones. If your city or county previously blocked ADUs through zoning, that ban is no longer valid.

What Is an ADU Under Florida Law?

Under Florida Statute §163.31771, an accessory dwelling unit is a secondary living space that includes its own kitchen, bathroom, and sleeping area. ADUs can be:

• Detached ADU: A separate structure on the same lot as the primary home (a backyard cottage, garage conversion, or newly built structure)
• Attached ADU: An addition connected to the main house with its own separate entrance
• Interior ADU: A self-contained unit created within the existing home, such as a finished basement or converted garage with a private entrance

Regardless of type, every ADU requires permits. Florida's building code applies the same structural, electrical, plumbing, and mechanical standards to an ADU that it does to any residential dwelling. For a full breakdown of what permits typically cost across project types, see our Florida building permit costs guide.

What Permits Do You Need for an ADU in Florida?

A detached ADU is essentially a new residential structure, so the permit requirements are similar to building a new home. Attached ADUs and interior conversions require permits for every system being modified. Here's what's typically involved:

• Building permit: Required for all structural work — framing, insulation, roofing, windows, and exterior
• Electrical permit: A dedicated electrical service or subpanel for the ADU, all wiring, outlets, lighting, and appliances
• Plumbing permit: New water supply lines, drain connections, and all fixtures in the ADU kitchen and bathroom
• Mechanical/HVAC permit: Cooling and heating for the ADU, whether a mini-split or an extension of the main system
• Gas permit (if applicable): If the ADU will have a gas range, water heater, or dryer

For a garage-to-ADU conversion, the permit requirements are nearly identical — see our Florida garage conversion permit guide for the full breakdown. If your ADU involves moving walls or structural elements, you'll also need engineered plans from a licensed Florida structural engineer.

What Did Florida SB-48 Change About ADU Rules?

Florida SB-48, effective July 1, 2026, is one of the biggest changes to Florida housing law in years. It amended Florida Statute §163.31771 to require all counties and municipalities to adopt ADU-friendly zoning ordinances by December 1, 2026. Specifically, SB-48 prohibits local governments from:

• Banning ADUs outright in single-family residential zones
• Capping ADU size below 500 square feet or refusing to allow ADUs up to 1,000 square feet
• Requiring owner-occupancy as a blanket condition of ADU approval
• Requiring a public hearing, variance, or other discretionary review just to approve an ADU that meets objective standards
• Requiring an HOA's approval as a prerequisite for issuing a building permit

Once a complete ADU application is submitted and the project meets objective code requirements, the local building department must approve it — they cannot drag the process out indefinitely. Local governments in Hillsborough County, Orange County, and across Florida retain authority over setback requirements, height limits, design standards, impact fees, and short-term rental regulations. But they can no longer use those controls to effectively ban ADUs.

How Much Does an ADU Permit Cost in Florida?

ADU permit costs vary significantly by county and project scope. A detached ADU is treated like new construction, so fees are calculated as a percentage of construction value. In Hillsborough County, total permit fees for a new ADU — including building, electrical, plumbing, and mechanical sub-permits — typically range from $1,000 to $3,000, depending on the unit's size and systems.

Permit fees are just one part of the cost equation. Impact fees are separate and can be significant. Impact fees vary dramatically by county and cover road, school, and utility infrastructure. In some Central Florida counties, ADU impact fees can add several thousand dollars to project costs — check with your county's building department for current rates before budgeting your project.

If you also need a Notice of Commencement, it must be recorded with the county clerk before construction begins — this is required for any project exceeding your county's dollar threshold, typically $2,500.

What Are the Setback and Zoning Rules for ADUs in Florida?

While SB-48 prevents Florida municipalities from banning ADUs, local governments retain authority over where on a lot an ADU can be placed. Setback requirements vary by municipality, but common ranges across Florida are:

• Rear setback: 5 to 10 feet from the rear property line
• Side setback: 5 feet from the side property line
• Separation from main dwelling: May require a minimum distance between a detached ADU and the primary home

Always confirm your parcel's specific setback requirements with your county or municipal planning department before finalizing the ADU design. The building permit application will require a site plan showing the ADU location, setbacks, and separation distances.

Note that while SB-48 preempts local zoning bans on ADUs, it does not override private deed restrictions or HOA covenants. If your HOA declaration prohibits accessory structures or requires architectural review board approval, you may face an HOA restriction even if your county's zoning now allows ADUs. Review your governing documents carefully before applying for a permit.

What Inspections Does an ADU Require in Florida?

ADU inspections follow the same sequence as any new residential construction in Florida. Expect inspections at these stages:

• Foundation/footing: Verifies footings meet design specs before concrete is poured
• Rough framing: Structural framing, hurricane straps, and sheathing reviewed before walls are closed
• Rough electrical, plumbing, and mechanical: All in-wall systems checked before drywall is installed
• Insulation: Verifies Florida Energy Code compliance for conditioned space
• Final inspection: Full review of the completed ADU
• Certificate of Occupancy (CO): Issued after final inspection; the ADU cannot legally be occupied until the CO is in hand

Missing or failed inspections at any stage can delay the project and create complications when you eventually sell the property. For a full picture of how open or expired permits can affect a home sale, read our guide on open permits and your Florida home sale.

Can You Build an ADU Without a Permit in Florida?

No. Building an ADU without permits in Florida carries the same serious consequences as any unpermitted construction: stop-work orders, fines, required demolition, insurance claim denials, and major complications when selling. An unpermitted ADU creates a cloud on the title that lenders and buyers will not overlook. Florida's new HB 803 permit exemption for repairs under $7,500 does not apply to new construction like ADUs — there's no exemption path for a new dwelling unit.

For a complete breakdown of consequences, see our guide on what happens if you build without a permit in Florida. If you already have an unpermitted ADU or in-law suite, contact your county building department about the after-the-fact permit process — expect fees at least double the standard rate and potentially require opening walls for inspection.

Skip the headache — tell us about your project and we'll match you with a licensed permit pro in your county.