An ADU builder in Jacksonville 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 Jacksonville'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 Jacksonville [14][15][16]
Based on our Jacksonville 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-$300,000 |
| Cost per Sq Ft | $150-$360 |
| Garage Conversion | $65,000-$130,000 |
| Prefab / Modular ADU (installed) | $125,000-$200,000 |
| City Permit & Plan Review | Building permit fees are set by Ordinance Code Chapter 320 on the gross floor area under roof, plus separate electrical, plumbing and mechanical permit fees; the city publishes no ADU-specific figure, so price it in JaxEPICS or with the Building Inspection Division (904-255-8500). |
| Impact Fees | Jacksonville's transportation Mobility Fee (Ordinance Code Ch. 655) is charged on new development that adds trips and must be paid before the vertical building permit issues; exemptions are listed in Sec. 655.109 and de minimis uses in Sec. 655.108. Ask the Concurrency and Mobility Management System Office (CMMSO@coj.net) whether a single ADU is exempt or de minimis before budgeting, and ask JEA about connection charges if the unit gets its own water or sewer service. |
For a full line-item breakdown, see our Jacksonville ADU cost guide. To confirm what you're allowed to build before you hire, review the Jacksonville ADU rules (max detached size: Building footprint capped at the lesser of 25% of the principal house's gross floor area or 750 sq ft (Sec. 656.403(g)(3)): a 2,000 sq ft house allows a 500 sq ft footprint, a 3,000 sq ft house the full 750 sq ft. The cap is on footprint, not floor area, and the unit must be behind the house and outside all required yards ((g)(1), (g)(4)).; owner-occupancy: Required in effect: the lot must carry an existing Duval County homestead exemption, or qualify for one that the owner has applied for through the Property Appraiser (Sec. 656.403(g)(6)), which makes the property the owner's permanent residence. Ordinance 2024-870 as filed would have deleted this rule; the Land Use and Zoning Committee struck that section on January 7, 2025 and the ordinance enacted January 14, 2025 left (g)(6) intact.).
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How to Vet an ADU Builder in Jacksonville
- 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 Jacksonville 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 (Building permit fees are set by Ordinance Code Chapter 320 on the gross floor area under roof, plus separate electrical, plumbing and mechanical permit fees; the city publishes no ADU-specific figure, so price it in JaxEPICS or with the Building Inspection Division (904-255-8500).), plan check (Electronic plan review in JaxEPICS by every discipline, including the fire marshal; the Florida Building Code 8th Edition (2023) and NEC 2020 apply. Lots in a FEMA flood zone are also reviewed by Development Services' Review Group.), and impact fees (Jacksonville's transportation Mobility Fee (Ordinance Code Ch. 655) is charged on new development that adds trips and must be paid before the vertical building permit issues; exemptions are listed in Sec. 655.109 and de minimis uses in Sec. 655.108. Ask the Concurrency and Mobility Management System Office (CMMSO@coj.net) whether a single ADU is exempt or de minimis before budgeting, and ask JEA about connection charges if the unit gets its own water or sewer service.) are included.
- Permit handling: Confirm they manage Jacksonville's permit process ("Building permit only, no zoning hearing: apply online in JaxEPICS (jaxepics.coj.net) to the Building Inspection Division (214 N. Hogan St., Room 280, 904-255-8500); zoning review happens inside the permit, and the application carries a mandatory certification that no deed restriction or HOA, neighborhood or master association rule bars an ADU (Sec. 656.403(g)(8)). Zoning questions: Zoning Section, Ed Ball Building Suite 300, 904-255-8300. A homeowner may pull the permit personally only for property for their own use that is not for sale or lease (owner's affidavit plus proof of homestead), so a unit built to rent should be permitted by a licensed contractor.", typically The city publishes no review clock for residential plan review; JaxEPICS returns comments once every discipline has reviewed the set. A permit expires after 180 days without work (Building Inspection Division FAQ).) 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 Jacksonville 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 (The city publishes no review clock for residential plan review; JaxEPICS returns comments once every discipline has reviewed the set. A permit expires after 180 days without work (Building Inspection Division FAQ).) 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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