Colorado ADU rules (2025)

Colorado’s new statewide baseline requires many jurisdictions to allow one ADU by administrative review starting June 30, 2025, while most design, size, and height specifics still live in local code.

TL;DR — Under HB24-1152, “subject jurisdictions” must allow one ADU by-right (administrative). HB24-1007 bans family-based occupancy caps statewide. Local size/height/setbacks still apply—use our HowTo below to confirm your city’s exact numbers.

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Detached ADU behind a single-family home in Colorado
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State baseline (effective 2025)

HB24-1152: ADU allowance in “subject jurisdictions”

  • Allowance: Must allow one ADU as an accessory use to a single-unit detached home via administrative approval (no public hearing) where single-unit homes are allowed. ({{verify locally to confirm your city’s status}})
  • Owner-occupancy: Cities cannot require owner-occupancy (limited exceptions at application time or for STR licensing). {{verify locally}}
  • Parking: No new off-street space required unless (a) parcel has zero off-street parking, and (b) the zone already required parking for the primary home as of 2024-01-01, and (c) on-street parking is prohibited on that block. {{verify locally}}
  • Setbacks: Side setbacks cannot exceed those for the primary; rear setback cannot exceed the greater of other accessory structures’ rear setback or 5 ft. {{verify locally}}
  • Size band: Local codes must allow ADUs somewhere in the 500–750 sf range (locals may allow smaller/larger; many do). {{verify locally}}
  • Extras: PUDs/HOAs in covered areas cannot add stricter ADU bans than local law; state creates grants, toolkit, and CHFA financing support pathways. {{verify locally}}

Law applies to “subject jurisdictions” (e.g., municipalities in MPOs and certain county areas). Outside those, locals may still allow ADUs by local ordinance.

Mini visual: state size floor

300 500 750 1000 Required local allowance band: 500–750 sf Locals may allow <500 or >800 as well

Note: Cities still define exact max size, height, and lot coverage. Treat this band as the required minimum allowance, then confirm your city’s specifics. {{verify locally}}

Colorado 6-point rule card

  1. Max size: Local; must at least allow a band within 500–750 sf. Many cities permit up to 800–1000+ sf or tie to main-home size. {{verify locally}}
  2. Height: Local (often 16–24 ft). {{verify locally}}
  3. Setbacks: Side ≤ primary’s side; rear ≤ max(other accessory rear, 5 ft). {{verify locally}}
  4. Parking: Generally no new off-street required except narrow cases; designation of an existing space may be required. {{verify locally}}
  5. Owner-occupancy: Prohibited (with limited procedural exceptions at application/STR licensing). {{verify locally}}
  6. Fees: Impact/utility fees may apply; supportive jurisdictions can tap state grants or reduce fees. {{verify locally}}

Permit HowTo (Colorado statewide flow)

  1. Confirm coverage: Use your address to check if you’re in a subject jurisdiction (MPO area city ≥1,000 population, or covered county area). {{verify locally}}
  2. Check local code page: Find your city/county ADU page for exact size/height/setbacks and any design rules. See resource links.
  3. Pre-design: Sketch footprint & utilities, decide detached vs. attached vs. internal conversion. Aim for 500–800 sf unless local rules allow more.
  4. Administrative review: Submit zoning/admin review package (site plan, elevations). No hearing should be required; approvals must be based on objective standards.
  5. Building permits: Full construction documents, energy/code compliance, contractor license (homeowner-builder allowances vary by city).
  6. Inspections & address: Expect multiple inspections; new address assignment common. Plan for utility coordination and meter policy. {{verify locally}}

Timeline varies widely. Many admins target 2–6 weeks for zoning review when plans are complete. {{verify locally}}

Official resources & portals

Colorado ADU FAQ

Does the state law legalize ADUs everywhere in Colorado?

No. It requires subject jurisdictions to allow one ADU by administrative review where single-unit homes are allowed. Outside those areas, local ordinances govern. {{verify locally}}

Can my city still require on-site parking for an ADU?

Only in narrow cases: no existing off-street parking, your zone required parking for the primary home as of 2024-01-01, and your block bans on-street parking. Otherwise, no new space can be required; designation of an existing space may be. {{verify locally}}

Is owner-occupancy still a thing?

Generally no; it’s prohibited, with limited procedural exceptions at application time or for short-term rental licensing. {{verify locally}}

What size ADU can I build?

The state requires locals to allow a band within 500–750 sf; many cities allow larger (e.g., 800–1000+ sf) or tie to the size of the main house. Check your city page. {{verify locally}}

Can HOAs block ADUs?

In covered areas, HOA/PUD provisions adopted after the law’s effective date cannot restrict ADUs beyond state/local allowances; some older covenants may also be void where the law applies. {{verify locally}}

Do these rules affect short-term rentals?

Local governments can still regulate STRs. Separately, HB24-1007 eliminates family-based occupancy caps statewide. {{verify locally}}

Updated • This page summarizes state law; always confirm current city/county code. {{verify locally}}