Zoning & Size Limits
| Requirement | Miami, FL | Austin, TX |
|---|
| Allowed Zones | Limited to select residential zones | SF3, SF2, SF1, MU, UR, etc. |
| Max Size (Detached) | 400-800 sq ft (varies by district) | 1,350 sq ft or 0.15 FAR (whichever is smaller; updated by HOME Phase 2, May 2024) |
| Max Size (Attached) | 400-800 sq ft (varies by district) | 1,350 sq ft or 0.15 FAR (whichever is smaller) |
| Max Height | Must not exceed height of principal structure | 35 feet |
| Parking Required | 2 spaces per unit | 1 space for primary, optional for ADU |
| Owner Occupancy | Not required | Not required |
Setback Requirements
| Setback | Miami, FL | Austin, TX |
|---|
| Rear Setback | 5 ft (RU-1 district) | 10 feet |
| Side Setback | 5 feet | 3 feet (with easement) |
| Front Setback | 25 feet | 20 feet |
Permits & Timeline
| Detail | Miami, FL | Austin, TX |
|---|
| Permit Timeline | 120-180 days | 45-60 days |
| Permit Fees | $5,000-$8,000 | $2,500-$4,000 |
| Impact Fees | $2,000-$3,500 | $1,200-$2,000 |
| Pre-Approved Plans | Not available | 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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