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 [12]
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 | Ordinance 28-052 (eff. Jan. 2023): new construction pays $5.50 per $1,000 of valuation to $50,000, then $4.50 per $1,000, with valuation set at $86/sq ft for 1-2 family work; an 800 sq ft unit values at $68,800 for a permit fee of about $360. First residential plan review is free. |
| Impact Fees | None. Ordinance 28-052 and the UDC contain no impact or capacity fee; water and sewer connection charges are billed separately by MAWSS |
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: No ADU size cap is codified (the 1,000 sq ft / 50% draft rule was not adopted). A second unit must fit the district lot coverage: R-1 Urban 50%, R-1 Suburban 35%, R-2 Urban 50%, R-2 Suburban 40%, R-A 35% (Secs. 64-2-4 to 64-2-6); owner-occupancy: No owner-occupancy rule exists in the UDC for ADUs or two-family dwellings; any condition would come from a BZA variance or Director determination).
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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 (Ordinance 28-052 (eff. Jan. 2023): new construction pays $5.50 per $1,000 of valuation to $50,000, then $4.50 per $1,000, with valuation set at $86/sq ft for 1-2 family work; an 800 sq ft unit values at $68,800 for a permit fee of about $360. First residential plan review is free.), plan check (Residential plan review through the CSS portal: no fee on first submittal, then $51, $101, $201 and $501 for the 1st-4th resubmittals; a $51 plan review fee applies in flood zones or for plans over 4,000 sq ft (Residential Plan Review Checklist, Jan. 2023)), and impact fees (None. Ordinance 28-052 and the UDC contain no impact or capacity fee; water and sewer connection charges are billed separately by MAWSS) are included.
- Permit handling: Confirm they manage Mobile's permit process ("Zoning first: ask Planning & Zoning (251-208-5895) whether your lot is R-2 or in the DDD, or request a similar-use determination / BZA variance for R-1. Then a residential building permit through Build Mobile's online CSS portal (2021 IRC, 2020 NEC, 2015 IECC); Historic District lots need an Architectural Review Board Certificate of Appropriateness and DDD lots a Consolidated Review Committee letter before permit", typically Not published. Build Mobile posts no target review time for residential plans; the residential checklist says to contact Permitting (251-208-7198) once all reviews are complete to schedule permit issuance.) 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 (Not published. Build Mobile posts no target review time for residential plans; the residential checklist says to contact Permitting (251-208-7198) once all reviews are complete to schedule permit issuance.) 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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