An ADU builder in Mobile 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 Mobile's permit process and utility connections. Not every general contractor has built one, so the right builder is one with ADU-specific experience in Alabama.
What ADU Builders Cost in Mobile [5]
Based on our Mobile 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) | $90,000-$175,000 |
| Cost per Sq Ft | $120-$195 |
| Garage Conversion | $40,000-$90,000 |
| Prefab / Modular ADU (installed) | $70,000-$150,000 |
| City Permit & Plan Review | Per the City of Mobile permit fee schedule — confirm current amounts with Build Mobile Permitting & Inspections Division |
| Impact Fees | None identified; confirm with Build Mobile Permitting & Inspections Division |
For a full line-item breakdown, see our Mobile ADU cost guide. To confirm what you're allowed to build before you hire, review the Mobile ADU rules (max detached size: 1,000 sq ft gross floor area or 50% of the principal structure's floor area, whichever is less (Sec. 64-4-2.B.3(a)); owner-occupancy: Not required by Sec. 64-4-2; confirm current administrative practice with Mobile Planning & Zoning).
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How to Vet an ADU Builder in Mobile
- License: Confirm a current contractor's license in Alabama 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 Mobile 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 (Per the City of Mobile permit fee schedule — confirm current amounts with Build Mobile Permitting & Inspections Division), plan check (Plan review submitted through the Build Mobile CSS online portal; confirm review times with Build Mobile), and impact fees (None identified; confirm with Build Mobile Permitting & Inspections Division) are included.
- Permit handling: Confirm they manage Mobile's permit process ("Building permit through Build Mobile's Permitting & Inspections Division (online CSS portal for plans, permits and inspections); ADUs in designated Historic Districts also need Architectural Review Board approval (Sec. 64-4-2.B.5(a)); all ADU structures must meet or be brought up to current Building Code (Sec. 64-4-2.B.5(b)). Contact: 251-208-5895", typically Confirm with Build Mobile Permitting & Inspections Division; pre-development meetings available) 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 Mobile 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 (Confirm with Build Mobile Permitting & Inspections Division; pre-development meetings available) 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 Alabama ADU client references?
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