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 [5][6]
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) | $180,000-$350,000 |
| Cost per Sq Ft | $240-$460 |
| Garage Conversion | $80,000-$180,000 |
| Prefab / Modular ADU (installed) | $120,000-$260,000 |
| City Permit & Plan Review | $5,000-$8,000 |
| Impact Fees | $2,000-$3,500 |
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: City of Miami: confirm current cap with City of Miami Planning (proposed ~500 sq ft / 10% of lot, capped at 800 sq ft). Unincorporated Miami-Dade: 400-800 sq ft in RU-1 districts (varies by district); owner-occupancy: Effectively required for rental: an ADU may be rented only if the primary residence is owner-occupied (homestead); same ownership required for both units. Unincorporated Miami-Dade County requires the owner to occupy the principal dwelling (the owner cannot live in the ADU).).
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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 ($5,000-$8,000), plan check (6-8 weeks), and impact fees ($2,000-$3,500) are included.
- Permit handling: Confirm they manage Miami's permit process ("By-right / administrative site-plan review + building permit in qualifying districts (a zoning variance is only needed for nonconforming or undersized lots)", typically 120-180 days) 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 (120-180 days) 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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