Boulder is highly supportive of ADU development, allowing both detached and attached units with streamlined approval. The city's emphasis on housing diversity and sustainability makes it one of Colorado's most ADU-friendly jurisdictions.
Zoning & Size Requirements
| Allowed Zones | All single-family and multi-family zones |
| Max Size (Detached) | 1,150 sq ft |
| Max Size (Attached) | 950 sq ft |
| Max Size (JADU) | 800 sq ft |
| Max Height | 35 feet |
| Max Units | 1 ADU per lot |
Setback Requirements
| Rear Setback | 10 feet |
| Side Setback | 3 feet |
| Front Setback | 15 feet |
| Parking Required | Optional |
| Owner Occupancy | Not required |
| Min Lot Size | 3,500 sq ft |
Permit Process & Fees
| Approval Process | Streamlined review process |
| Review Timeline | 40-60 days |
| Permit Fees | $1,900-$3,200 |
| Impact Fees | Minimal |
| Plan Check | 2-3 weeks |
| Pre-Approved Plans | Available |
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Construction Costs
| Average Build Cost | $160,000-$320,000 |
| Cost per Sq Ft | $140-$280 |
| Garage Conversion | $80,000-$180,000 |
| Prefab ADU (Installed) | $120,000-$270,000 (installed) |
Finance Your ADU Project
Most ADU projects are funded through HELOCs, construction loans, or cash-out refinancing. Compare rates from top lenders in minutes.
Compare ADU Financing Options →Rental Income Potential
| Avg Rent (1 Bedroom) | $1,600-$2,100/mo |
| Avg Rent (2 Bedroom) | $2,000-$2,800/mo |
| Short-Term Rental | Limited restrictions |
| Est. Annual ROI | 6-8% annual return |
Explore Prefab ADU Options
Prefab ADUs can save 20-40% vs. traditional construction and cut build time in half. Compare top prefab manufacturers.
Compare Prefab ADUs →Recent Law Changes
What's Changed Recently
- 2024: Expanded ADU size allowances
- 2023: Eliminated parking requirement for ADUs
- 2024: Streamlined approval for owner-occupied projects
- 2023: Created ADU affordability incentive program
Tips for Building an ADU in Boulder
- Boulder's tech and university scene creates strong rental demand
- Higher construction costs but excellent rental income potential
- Sustainability focus aligns with modern ADU development trends
- Short-term rental market viable in this college town location
Frequently Asked Questions
Can I build an ADU in Boulder?
Yes. ADUs are allowed in All single-family and multi-family zones in Boulder. The maximum size for a detached ADU is 1,150 sq ft. No owner-occupancy is required.
How much does an ADU cost in Boulder?
ADU construction in Boulder typically costs $160,000-$320,000. Garage conversions run $80,000-$180,000, and prefab ADUs cost $120,000-$270,000 (installed).
How much can I rent an ADU for in Boulder?
Average ADU rents in Boulder are $1,600-$2,100/mo for a 1-bedroom and $2,000-$2,800/mo for a 2-bedroom unit.
Do I need parking for an ADU in Boulder?
Optional. Check with Boulder planning department for the latest Colorado ADU parking rules, as many states have relaxed requirements in recent years.
How long does it take to get an ADU permit in Boulder?
The permit review timeline in Boulder is 40-60 days. Fees range from $1,900-$3,200.
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