Everything homeowners ask about building an ADU in Denver — answered with 2026 data.
Yes, ADUs are allowed in All residential zones in Denver, CO. The maximum size for a detached ADU is 864 sq ft. Attached ADUs can be up to 864 sq ft. Denver has an ADU-friendliness score of 8/10. Check our full Denver ADU rules page for complete zoning details.
ADU construction in Denver typically costs $140,000-$280,000. The cost per square foot averages $130-$260. Garage conversions are more affordable at $70,000-$160,000, while prefab ADUs cost $100,000-$230,000. Permit fees add $1,600-$2,700 to your budget. See our detailed Denver ADU cost guide.
Detached ADUs in Denver can be up to 864 sq ft. Attached ADUs are limited to 864 sq ft. Junior ADUs (JADUs) have a cap of 800 sq ft. Maximum height is 24 ft maximum. You are allowed up to 1 detached + 1 attached per lot on a qualifying lot.
Rear setback: Must be within rear 35% of lot; 5 ft minimum rear setback. Side setback: 3 feet. Front setback: 15 feet. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
1 space per unit. Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Required in single-unit zones (owner must live in primary or ADU). Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in Denver is typically 30-45 days. The plan check process takes approximately 1-2 weeks. Pre-approved plans availability: Extensive library available.
Average ADU rental income in Denver: 1-bedroom units rent for $1,400-$1,900/mo/month, 2-bedroom units for $1,800-$2,500/mo/month. Short-term rentals: Yes, with STR license. Expected ROI: 7-9% annual return.
The minimum lot size for an ADU in Denver is 3,500 sq ft. This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In Denver, a garage conversion typically costs $70,000-$160,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.