Zoning & Size Limits
| Requirement | Miami, FL | Austin, TX |
|---|
| Allowed Zones | City of Miami: ADUs allowed in T3-L under Miami 21; a propos | SF3, SF2, SF1, MU, UR, etc. |
| Max Size (Detached) | City of Miami: confirm current cap with City of Miami Planning (proposed ~500 sq ft / 10% of lot, capped at 800 sq ft). Unincorporated Miami-Dade: 400-800 sq ft in RU-1 districts (varies by district) | Lesser of 1,100 sq ft or 15% of lot area (HOME Initiative). 2nd-story floor area capped at 550 sq ft. |
| Max Size (Attached) | See max_size_detached — confirm with City of Miami Planning | Lesser of 1,100 sq ft or 15% of lot area (HOME Initiative) |
| Max Height | Must not exceed height of principal structure | 30 feet (2 stories typical under HOME) |
| Parking Required | Maximum 1 additional space (no more than 2 vehicles); must b | No off-street parking required for ADUs under 550 sq ft; 1 s |
| Owner Occupancy | Effectively required for rental: an ADU may be rented only i | Not required |
Setback Requirements
| Setback | Miami, FL | Austin, TX |
|---|
| Rear Setback | 5 ft (RU-1 district) | 10 feet |
| Side Setback | 5 feet | 5 feet |
| Front Setback | 25 feet | 25 feet |
Permits & Timeline
| Detail | Miami, FL | Austin, TX |
|---|
| Permit Timeline | 120-180 days | Confirm with Austin Development Services Department (typical 45-90 days) |
| Permit Fees | $5,000-$8,000 | $2,500-$4,000 |
| Impact Fees | $2,000-$3,500 | $1,200-$2,000 |
| Pre-Approved Plans | Yes — Miami-Dade County ADU Blueprint program offe | City offers expedited review for pre-approved plan |
Construction Costs
| Cost | Miami, FL | Austin, TX |
|---|
| Avg Build Cost | $180,000-$350,000 | $125,000-$250,000 |
| Cost Per Sq Ft | $240-$460 | $165-$330 |
| Garage Conversion | $80,000-$180,000 | $60,000-$140,000 |
| Prefab ADU | $120,000-$260,000 | $85,000-$200,000 |
Rental Income Potential
| Rental | Miami, FL | Austin, TX |
|---|
| 1BR Avg Rent | $1,600-$2,200/mo | $1,300-$1,900/mo |
| 2BR Avg Rent | $2,000-$3,000/mo | $1,700-$2,500/mo |
| Short-Term Rentals | Not permitted | Check local restrictions |
| Est. ROI | 5-7% annual return | 7-10% annual return |
Which City Is Better for ADUs?
Miami scores 5/10 while Austin scores 8/10 on our ADU-friendliness index.
Austin 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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