Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your Mobile ADU cost →Building an ADU in Mobile costs between $90,000-$175,000 for new construction, with per-square-foot costs averaging $120-$195. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $40,000-$90,000, while prefab/modular ADUs fall in between at $70,000-$150,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & Fees | 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 |
| Site Prep & Foundation | $10,000 – $35,000 |
| Framing & Structure | $15,000 – $45,000 |
| Plumbing | $8,000 – $20,000 |
| Electrical | $5,000 – $15,000 |
| HVAC | $3,000 – $8,000 |
| Interior Finishes | $15,000 – $40,000 |
Quotes for the same ADU commonly vary 20–40% between builders. Get up to 3 free quotes from ADU builders serving Mobile — no obligation.
Get Mobile builder quotes →Permit fees in Mobile are Per the City of Mobile permit fee schedule — confirm current amounts with Build Mobile Permitting & Inspections Division. The review timeline is Confirm with Build Mobile Permitting & Inspections Division; pre-development meetings available, with plan check: Plan review submitted through the Build Mobile CSS online portal; confirm review times with Build Mobile. Impact fees are None identified; confirm with Build Mobile Permitting & Inspections Division. Pre-approved plans: None.
| 1-Bedroom Rent | $1,000-$1,200/month |
| 2-Bedroom Rent | $1,150-$1,450/month |
| Annual Rental Income (est.) | $13,200/year |
| Payback Period (est.) | 10.0 years |
| Short-Term Rental | Not addressed in the ADU section (Sec. 64-4-2) — confirm short-term rental rules with Mobile Planning & Zoning before listing |
| Overall ROI Estimate | 5-8% annual return |
A typical ADU in Mobile generates approximately $13,200 per year in rental income based on average 1-bedroom rents. At an average construction cost of $132,500, the estimated payback period is 10.0 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in Mobile and varies by market (often less than build cost).
1. Garage conversions save 40-60% vs new construction since the shell already exists. Average cost in Mobile: $40,000-$90,000.
2. Prefab/modular ADUs offer predictable pricing and faster timelines. Average: $70,000-$150,000.
3. Pre-approved plans — Mobile does not offer a pre-approved/standard ADU plan program yet, so budget for custom architectural plans (typically $3,000-$15,000).
4. State grants — California's CalHFA ADU grant (up to $40K) is currently paused; check calhfa.ca.gov/adu for status and your state for active programs.
5. Get multiple bids — ADU contractor pricing varies 20-40% for the same project. We recommend getting at least 3 quotes.
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