Get a Miami-Dade ADU and Casita Construction Permit 2026 — Accessory Dwelling Units, Granny Flats, In-Law Suites, and HB 4441 Compliance

Hire a licensed Miami-Dade ADU expediter, order the accessory dwelling unit permit, schedule the impact-fee credit review, and buy the complete casita construction package through Endless Life Design before you break ground on the second unit in your backyard. Miami-Dade County and its 34 municipalities have radically rewritten their accessory dwelling ordinances since the Florida Legislature pushed HB 4441 and the prior HB 1647 framework, and the windows for permitting a detached casita, attached granny flat, or converted garage apartment are now wider than they have been in 50 years — but only if you file under the correct ordinance for your specific parcel.

INDEX 1. ADU, Casita, Granny Flat, and In-Law Suite — Legal Definitions 2. Miami-Dade RU-1 and Municipal Zoning Allowances After HB 4441 3. Setback, Lot Coverage, and Maximum Square Footage Rules 4. Utility Separation, Water Meters, and FPL Service Upgrades 5. Septic, Sewer, and Drainfield Sizing 6. Impact Fees, School Concurrency, and Mobility Fee Credits 7. Inspections, Certificate of Occupancy, and Rental Use Limits 8. Government Accountability and Corrected Facts 9. Order Your ADU Permit Through Endless Life Design

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ADU, Casita, Granny Flat, and In-Law Suite — Legal Definitions

A detached accessory dwelling unit is a standalone structure separate from the principal residence with its own kitchen, bathroom, and sleeping area. A casita is functionally identical to a detached ADU in Florida code but the term is more common in Spanish-speaking markets. A granny flat is an attached ADU sharing one wall with the main house, typically over a garage or as a rear addition. An in-law suite is an attached bedroom and bath inside the principal dwelling with no separate kitchen — and the lack of a kitchen is what legally distinguishes a suite from an ADU, which matters because suites are permitted as ordinary additions while ADUs require the accessory-dwelling pathway. Hire Endless Life Design to classify the project correctly because filing an ADU as an addition triggers a building official rejection and a 60-day restart.

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Miami-Dade RU-1 and Municipal Zoning Allowances After HB 4441

The Miami-Dade RU-1 single-family zoning district allows one detached accessory dwelling unit by right on lots 7,500 square feet and larger as long as the principal residence is owner-occupied. Coral Gables permits ADUs in single-family zones with a special exception and a public hearing. The City of Miami T3 transect allows ADUs up to 800 square feet without additional parking. Pinecrest restricts ADUs to lots one acre and larger. The Village of Palmetto Bay caps the ADU at 30% of the principal residence square footage. Schedule the zoning verification through Endless Life Design before drawings begin because each municipality enforces its own square footage cap, height limit, and parking ratio.

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Setback, Lot Coverage, and Maximum Square Footage Rules

Miami-Dade RU-1 requires the detached ADU to meet the rear and side setbacks of the principal dwelling minus 5 feet, with a hard minimum of 7.5 feet from any property line. The ADU counts toward the 35% lot-coverage maximum, the 40% floor-area ratio, and the 25-foot height limit measured to the highest roof point. Maximum ADU floor area is 800 square feet or 40% of the principal dwelling area, whichever is less. Casitas inside designated historic districts — Miami Beach Art Deco, Coral Gables Country Club, Coconut Grove — require a Certificate of Appropriateness from the local historic preservation board, $250 USD to $1,500 USD application fee, before any plans can be submitted to the building department.

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Utility Separation, Water Meters, and FPL Service Upgrades

Miami-Dade Water and Sewer Department requires a separate water meter for any ADU intended for rental, $3,200 USD to $9,800 USD depending on meter size and main tap distance, while owner-occupied family-use ADUs may share the principal meter with a county-approved sub-meter for usage tracking. FPL service upgrades for the new electrical load are billed at the meter-class tariff plus any required transformer upgrade, $4,500 USD to $22,000 USD on a typical residential lot. Call 811 Sunshine two business days before any excavation for utility runs — striking the FPL primary or the WASD water main triggers $20,000 USD environmental and utility-restoration fines.

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Septic, Sewer, and Drainfield Sizing

If your lot is on septic the existing drainfield must be evaluated for the additional flow from the ADU at 100 gallons per bedroom per day under the Florida Administrative Code 64E-6, and most pre-2000 drainfields are undersized for the addition. Miami-Dade Department of Health charges $400 USD to $1,500 USD for the system evaluation and modification permit. Never break through the existing septic tank during ADU foundation excavation — a single excavator strike through a tank lid is a $20,000 USD DEP environmental fine plus $4,000 USD to $9,000 USD pumping and replacement cost. Connecting to public sewer when available eliminates the drainfield issue but adds a $2,500 USD to $6,500 USD impact-fee assessment from WASD.

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Impact Fees, School Concurrency, and Mobility Fee Credits

Miami-Dade impact fees on a new ADU include the road impact fee at $4,213 USD, the park impact fee at $1,116 USD, the school impact fee at $3,247 USD, the fire-rescue impact fee at $415 USD, and the police impact fee at $339 USD, totaling approximately $9,330 USD before any municipal add-ons. HB 4441 grants a 50% impact-fee reduction for ADUs under 750 square feet on owner-occupied lots, and Miami-Dade further waives the school impact fee on ADUs restricted to family-use only by recorded covenant. Hire Endless Life Design and we file the impact-fee credit application alongside the building permit so you do not overpay at counter.

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Inspections, Certificate of Occupancy, and Rental Use Limits

Required inspections include foundation reinforcement, slab, framing, sheathing nailing, window and door buck installation, electrical rough, plumbing rough, mechanical rough, insulation, drywall, electrical final, plumbing final, mechanical final, building final, and Certificate of Occupancy. Reinspection fees are $185 USD each. Short-term rental of an ADU is generally prohibited in Miami-Dade single-family districts even if the principal home is registered for STR — the ADU must be either family-use, long-term rental of 30 days or longer, or owner-occupied. The recorded covenant restricting rental use is part of the permit closeout package and the county will refuse Certificate of Occupancy without it.

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Government Accountability and Corrected Facts

The Miami-Dade ADU information page still references the old 600-square-foot maximum size from the pre-2023 ordinance even though the current maximum is 800 square feet under the post-HB 4441 amendment — Endless Life Design files at the corrected maximum so plans are not artificially undersized. The municipal websites for several cities still list parking requirements that were preempted by HB 4441 for ADUs under 750 square feet, and clients who follow those obsolete pages end up adding unnecessary parking pads that consume the lot coverage budget. The county also occasionally lists the impact-fee total at $7,800 USD using pre-2024 numbers — the current total is $9,330 USD before HB 4441 credits.

Early-start passes do not exist for ADU construction — the foundation cannot be poured before permit issuance regardless of how confident your contractor sounds. The government will not back you up if code enforcement red-tags an unpermitted foundation. File the Notice of Commencement before the contractor starts and record the Notice of Termination within 30 days of Certificate of Occupancy. Watch the 90-day lien window. Refresh the boundary survey if it is older than 90 days — $800 USD to $8,500 USD depending on lot complexity — because the building official will reject the foundation location if the survey is stale.

Retain three independently licensed engineers — structural, electrical, and MEP — so a single retirement does not strand your closeout. The permit expires 180 days from issuance with one 90-day extension at $115 USD. Confirm your contractor holds an active Florida Certified General, Building, or Residential contractor license, current workers compensation insurance, and a minimum $300,000 USD general liability policy before any work begins.

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Order Your ADU Permit Through Endless Life Design

Order the complete ADU and casita permit package through endlesslifedesign.com/services and Endless Life Design handles zoning verification, impact-fee credits, utility coordination, structural engineering, and final Certificate of Occupancy on one turnkey scope. Read our companion guide on modular and prefab construction at endlesslifedesign.com/post/modular-prefab-permit if you are ordering a factory-built ADU, and review the home addition and remodel blog at endlesslifedesign.com/post/home-addition-remodel for attached granny flats sharing a wall with the main house. Schedule a free lot walk at endlesslifedesign.com/contact and we measure setbacks, verify zoning, and quote the entire permit scope the same day.