Zoning & Size Limits
| Requirement | Mobile, AL | Huntsville, AL |
|---|
| Allowed Zones | Permitted as an accessory use per the UDC Use Table; one ADU | None — detached/backyard ADUs are prohibited citywide (Sec. |
| Max Size (Detached) | 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)) | N/A — detached ADUs prohibited (Sec. 73.5; Sec. 10.6.3 bans kitchens in detached accessory structures) |
| Max Size (Attached) | Same standard — 1,000 sq ft or 50% of principal structure, whichever is less; may be adapted from a portion of the principal dwelling | No size cap for an interior second-kitchen suite, but it must share an interior wall with and be directly accessible from the main living areas (Sec. 10.6.2) — no separation by garage, breezeway or porch |
| Max Height | 2 stories or the height of the principal dwelling, | N/A for ADUs; accessory structures follow district |
| Parking Required | At least 1 off-street parking space for the ADU (Sec. 64-4-2 | N/A — no ADU standard exists |
| Owner Occupancy | Not required by Sec. 64-4-2; confirm current administrative | Required for second-kitchen suites: owner must occupy the dw |
Setback Requirements
| Setback | Mobile, AL | Huntsville, AL |
|---|
| Rear Setback | Same as underlying zoning district rear-yard setback, or Historic District Overlay if applicable (Sec. 64-4-2.B.4(a)) — confirm district value with Mobile Planning & Zoning | N/A for ADUs — rear dwellings prohibited |
| Side Setback | Same as underlying district side-yard setback (Sec. 64-4-2.B.4(a)) | N/A for ADUs |
| Front Setback | Same as underlying district front-yard setback (Se | N/A for ADUs |
Permits & Timeline
| Detail | Mobile, AL | Huntsville, AL |
|---|
| Permit Timeline | Confirm with Build Mobile Permitting & Inspections Division; pre-development meetings available | N/A for ADUs; confirm second-kitchen and building-permit timelines with Huntsville Planning & Zoning Services |
| Permit Fees | Per the City of Mobile permit fee schedule — confirm current amounts with Build Mobile Permitting & Inspections Division | Confirm with Huntsville Development Services |
| Impact Fees | None identified; confirm with Build Mobile Permitting & Insp | None identified; confirm with Huntsville Development Service |
| Pre-Approved Plans | None | None |
Construction Costs
| Cost | Mobile, AL | Huntsville, AL |
|---|
| Avg Build Cost | $90,000-$175,000 | $95,000-$185,000 |
| Cost Per Sq Ft | $120-$195 | $125-$200 |
| Garage Conversion | $40,000-$90,000 | $40,000-$95,000 |
| Prefab ADU | $70,000-$150,000 | $70,000-$150,000 |
Rental Income Potential
| Rental | Mobile, AL | Huntsville, AL |
|---|
| 1BR Avg Rent | $1,000-$1,200/mo | $1,000-$1,200/mo |
| 2BR Avg Rent | $1,150-$1,450/mo | $1,150-$1,400/mo |
| Short-Term Rentals | Not addressed in the ADU section (Sec. 64-4-2) — confirm sho | Moot — ADUs are not legal, and a dwelling with a second kitc |
| Est. ROI | 5-8% annual return | 5-8% annual return (hypothetical — ADUs currently prohibited) |
Which City Is Better for ADUs?
Mobile scores 6/10 while Huntsville scores 2/10 on our ADU-friendliness index.
Mobile edges ahead overall. Both cities offer viable ADU development opportunities — the best choice depends on your specific property, budget, and goals.
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