Everything homeowners ask about building an ADU in Denver — answered with 2026 data.
Yes, ADUs are allowed in All zone districts that allow a single-unit dwelling, citywide since CB24-1303 (eff. Dec 16, 2024), including Former Chapter 59 districts and PUDs that permit single-unit homes (DZC 11.8.2.3 bars ADU prohibitions in PUDs). ADUs accessory to duplex, row-house or multi-unit buildings must be detached (DZC 11.8.2.1.A.2). Check your district on Denver's ADU map. in Denver, CO. The maximum size for a detached ADU is SU districts: ADU gross floor area 864 sq ft on lots of 7,000 sq ft or less, 1,000 sq ft on larger lots (DZC 11.8.2.1.B.2); the detached ADU building footprint is capped at the same 864/1,000 sq ft (e.g., DZC 5.3.4.5.A). Other districts: 1,000 sq ft footprint per unit, GFA not separately capped. Attached ADUs can be up to SU districts: 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 $200,000-$450,000. The cost per square foot averages $250-$500. Garage conversions are more affordable at $80,000-$150,000, while prefab ADUs cost $175,000-$425,000. Permit fees add Building permit is valuation-based: $770 + $5.60 per $1,000 over $100,000 (about $1,330 at $200,000) plus a 50% plan-review fee; zoning permit $150 + $0.50 per $1,000; SUDP $425 application + $150 inspection; Denver Water ADU system development charge $2,170 (from Jul 1, 2026). to your budget. See our detailed Denver ADU cost guide.
Detached ADUs in Denver can be up to SU districts: ADU gross floor area 864 sq ft on lots of 7,000 sq ft or less, 1,000 sq ft on larger lots. Attached ADUs are limited to SU districts: 864 sq ft. Junior ADUs (JADUs) have a cap of No JADU category in the Denver Zoning Code; a basement or in-house unit is an attached ADU under the caps above, and only one kitchen (partial or full) is allowed per ADU (DZC 11.8.2.1.C.3). Maximum height is Detached ADU: 2 stories / 24 ft in Urban (U-) districts; in E-SU and S-SU districts either 1 story / 17 ft (Option A) or 2 stories / 24 ft (Option B, which requires the deeper Option B rear setback). Bulk plane starts 10 ft (12 ft on lots 40 ft wide or less in U-/E-) above the side lot line and rises at 45 degrees (DZC 3.3.4.5.A, 4.3.4.5.A, 5.3.4.5.A). You are allowed up to 1 ADU per primary dwelling unit on a qualifying lot.
Rear setback: U- districts: 5 ft, or 0 ft where an alley abuts the rear line and no garage door faces it. E-SU: 5 ft where an alley or street abuts the rear; otherwise 5 ft (1-story) or 12 ft (2-story). S-SU: 10 ft (1-story) or 20 ft (2-story). The detached ADU must sit in the rear 35% of lot depth (U-, E-) or rear 50% (S-) (DADU building form tables). Side setback: U- and E- districts: 3 ft on lots 40 ft wide or less, 5 ft on wider lots (side street the same). S-SU: 3 ft (lots 25 ft or narrower), 5 ft (25-62 ft wide), 7.5 ft (62 ft or wider). State law bars ADU side setbacks larger than the house's (C.R.S. 29-35-102(18)). Front setback: Not applicable to a detached ADU, which must be behind the house in the rear 35% (U-, E-) or rear 50% (S-) of the zone lot depth; the zoning code sets no minimum separation from the house (building-code fire separation applies). An attached ADU follows the house's primary-street setback. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
None. Denver removed all minimum vehicle parking citywide by the Modernizing Parking Requirements text amendment (adopted Aug 4, 2025, eff. Aug 11, 2025). Vehicle access must come from the alley where one exists, and the ADU may not have its own driveway except new alley access (DZC 11.8.2.1.C.1). Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Only at the time of permit application, and only in single-unit (SU) districts: an owner must live in the existing house as their primary residence (shown by two of driver's licence, vehicle or voter registration, tax documents, utility bill). Waived when house and ADU are built together; no ongoing requirement (DZC 11.8.2.2.B, per CB24-1303 and C.R.S. 29-35-103(2)(b)). ADU and house must stay under one ownership (11.8.2.2.A). 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 Not published as a fixed figure: Denver's Average Plan Review Times dashboard (updated daily) shows current 'Major Residential' review times. Trade permits for new construction need the issued residential construction permit first (since May 22, 2025). Plan check: Zoning, building and SUDP reviews run concurrently when all required documents are uploaded with the initial application; a property survey is needed if building within 3 ft of a lot line. New construction over 500 sq ft also needs an approved URCO waste-diversion plan and refundable deposit before the permit issues. Pre-approved plans availability: None: Denver CPD offers no pre-approved ADU plan set (only a sample site plan and elevations, checked Sept 2026). Any plan or fee help under Colorado's HB 24-1152 grant program would be announced by the city, not by this page.
Average ADU rental income in Denver: 1-bedroom units rent for $1,650-$2,000/month, 2-bedroom units for $2,000-$2,500/month. Short-term rentals: Yes, with a Denver STR licence: the host's primary residence must be on the same lot; an ADU accessory to a single-unit home may be the STR, but not if the host lives in the ADU (DZC 11.8.10.1.C, F). Expected ROI: 5-8% gross rental yield on build cost.
The minimum lot size for an ADU in Denver is No separate minimum lot size for an ADU; CB24-1303 deleted the 16 ADU-only '-1' districts. The only lot-size step is the floor-area/footprint cap: 864 sq ft on lots of 7,000 sq ft or less, 1,000 sq ft above that. 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 $80,000-$150,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.
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