An ADU builder in Miami is a licensed contractor who designs and constructs accessory dwelling units — detached backyard units, garage conversions, attached additions, and junior ADUs (JADUs). Because an ADU is a complete second dwelling, the builder coordinates foundation, framing, plumbing, electrical, and HVAC work and pulls it through Miami's permit process and utility connections. Not every general contractor has built one, so the right builder is one with ADU-specific experience in Florida.
What ADU Builders Cost in Miami [10][11]
Based on our Miami cost data, expect the following ranges from local ADU builders. Quotes for the same scope typically vary 20-40% between contractors, so getting at least three bids is the single best way to control cost.
| New Detached ADU (all-in) | $150,000-$320,000 |
| Cost per Sq Ft | $250-$450 |
| Garage Conversion | $80,000-$160,000 |
| Prefab / Modular ADU (installed) | $130,000-$250,000 |
| City Permit & Plan Review | About $2,200-$3,500 in city building fees on a $200,000-$350,000 unit: 0.50% of construction cost (min $110), $2.80 per $1,000 up-front, solid-waste $0.22 per $100 (max $600), energy $0.11/sq ft, CO $105 (Res. R-26-0200, 4/23/2026); zoning $250 up-front; impact fees extra. |
| Impact Fees | City impact fees (City Code Ch. 13) plus Miami-Dade County mobility and school fees. The County's 2024-2027 rate sheet lists single-family detached at $9,275-$10,625 (mobility) plus $612 per unit and $0.918 per sq ft (school); the sheet has no ADU line, so request a written estimate before you design. |
For a full line-item breakdown, see our Miami ADU cost guide. To confirm what you're allowed to build before you hire, review the Miami ADU rules (max detached size: 10% of lot area, up to 800 sq ft; the cap cannot be Waived (Art. 6 Table 13). Minimum sizes: 275 sq ft efficiency, 450 sq ft one-bedroom, 550 sq ft two-bedroom. A 5,000 sq ft lot therefore allows 500 sq ft; you need an 8,000 sq ft lot to reach 800 sq ft.; owner-occupancy: House and ADU must be under the same ownership, and the ADU may be rented only while the property has current homestead status, so in practice the owner must live on site to rent it. The unit must be used predominantly as permanent housing and is subject to registration and annual renewal under the City Code (Sec. 3.18).).
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How to Vet an ADU Builder in Miami
- License: Confirm a current contractor's license in Florida and that it's in good standing. Ask for the license number and verify it with the state board.
- ADU-specific experience: Ask how many ADUs they've completed in or near Miami and request addresses or photos. ADU permitting and setbacks differ from a kitchen remodel.
- Portfolio & references: Get references from recent ADU clients and, if possible, visit a finished unit.
- Insurance: Verify general liability and workers' compensation coverage. Ask for a certificate of insurance.
- Written, detailed bid: Insist on an itemized, fixed-price or clearly-scoped bid — not a verbal estimate. It should state whether permits (About $2,200-$3,500 in city building fees on a $200,000-$350,000 unit: 0.50% of construction cost (min $110), $2.80 per $1,000 up-front, solid-waste $0.22 per $100 (max $600), energy $0.11/sq ft, CO $105 (Res. R-26-0200, 4/23/2026); zoning $250 up-front; impact fees extra.), plan check (Not published; F.S. 553.792 sets a 30-business-day clock per review cycle, and re-reviews after the second cycle cost $56 per discipline), and impact fees (City impact fees (City Code Ch. 13) plus Miami-Dade County mobility and school fees. The County's 2024-2027 rate sheet lists single-family detached at $9,275-$10,625 (mobility) plus $612 per unit and $0.918 per sq ft (school); the sheet has no ADU line, so request a written estimate before you design.) are included.
- Permit handling: Confirm they manage Miami's permit process ("By right: building permit through the City of Miami Building Department (zoning review is part of the permit); no Warrant or hearing. A Waiver is needed only to adjust a setback by up to 10%. Register the ADU with the City and renew annually (Sec. 3.18).", typically Not published by the City. Florida Statute 553.792 gives the City 30 business days to review a complete residential application per cycle; plan on 3-6 months from submittal to permit including re-reviews and Miami-Dade County sign-offs.) and who is responsible if revisions are required.
- Payment schedule: Avoid large upfront payments. A reasonable schedule ties payments to completed milestones.
Questions to Ask Before You Hire
- How many ADUs have you built in Miami in the last two years?
- Is your bid fixed-price, and what would trigger a change order?
- Are permits, plan check, and utility connection fees included?
- What's a realistic timeline, including permit review (Not published by the City. Florida Statute 553.792 gives the City 30 business days to review a complete residential application per cycle; plan on 3-6 months from submittal to permit including re-reviews and Miami-Dade County sign-offs.) and construction?
- Who is my point of contact and how are delays communicated?
- What warranty do you provide on workmanship?
- Can you share three recent Florida ADU client references?
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