ADU Regulations in Colorado (CO)
Colorado is rated Easy for ADU construction with an ADU-friendliness score of 83/100 (Very ADU-Friendly). Colorado has a statewide ADU law that sets baseline rules across all municipalities. No owner-occupancy requirement. No additional parking required for ADUs. Colorado passed HB 24-1152 in 2024, requiring all municipalities to allow ADUs on single-family lots. The law prohibits local bans, limits parking requirements, and caps owner-occupancy mandates. Effective 2025 for cities over 1,000 population. ADUs can be rented long-term or short-term depending on local rules.
Full ADU Regulations Summary for Colorado
| ADUs Allowed | Yes |
| Statewide ADU Law | Yes |
| Maximum ADU Size | Set locally |
| Owner Occupancy Required | No |
| Parking Required | No |
| Minimum Setback | 5 ft |
| Permitting Timeline | 90 days max |
| Impact Fees | Limited by state law |
| Long-Term Rental Allowed | Yes |
| Short-Term Rental (Airbnb) Allowed | Yes |
| Ease of Building | Easy |
ADU Regulations by City in Colorado
ADU rules can vary by city even within the same state. While Colorado's statewide law sets minimum standards, some cities have additional local provisions. Below are ADU details for 4 cities in Colorado.
Denver
Denver allows ADUs by right on single-family lots. Detached ADUs up to 1,000 sq ft. No owner-occupancy requirement. No additional parking required.
Colorado Springs
ADUs permitted in residential zones per state law. City updated zoning in 2025 for compliance.
Boulder
ADUs allowed on most residential lots. Boulder had permissive ADU rules before the state law. Detached ADUs up to 800 sq ft.
Fort Collins
ADUs permitted by right. City allows both attached and detached ADUs. No additional parking required.
Colorado's 2024 ADU Law: What Actually Changed on June 30, 2025
Colorado moved from pure local control to a state mandate with HB24-1152 (signed May 13, 2024, codified at C.R.S. § 29-35-401 et seq.). Since June 30, 2025, a "subject jurisdiction" must allow one ADU as an accessory use to a single-family home, by administrative approval, everywhere it allows single-family homes — meaning objective written standards, no public hearing, and no discretionary vote by a council or planning commission.
Which cities are covered: municipalities with 1,000+ residents inside a metropolitan planning organization (the Front Range from Fort Collins through Denver to Pueblo, plus the Grand Valley around Grand Junction), and the urbanized parts of counties in large census-designated places within an MPO. Small towns and rural counties outside MPOs keep full local control — so if you're outside the metro areas, your county's code still decides.
What Covered Cities Can No Longer Require
- No new parking space for the ADU — except one space where the parcel has no off-street parking at all, the zone required parking as of Jan 1, 2024, and on-street parking is prohibited on that block.
- No owner-occupancy requirement. A city may only require that the owner live on the parcel at the time of the application to build or convert — or to hold a short-term-rental license for the ADU — not as an ongoing condition of renting it long-term.
- No "restrictive design or dimension standards." Cities must permit ADUs of 500–750 sq ft, can't impose side setbacks larger than the main house's, rear setbacks over 5 feet (beyond normal accessory-building rules), stricter minimum lot sizes than single-family, or stricter aesthetic rules for factory-built ADUs.
- HOA bans don't override the law in covered jurisdictions, per Colorado DOLA.
What cities can still do: charge impact fees, enforce building and life-safety codes, regulate short-term rental of ADUs, and allow bigger or additional ADUs if they choose. Exempt parcels: those without water/sewer service (or where a well can't support another unit), historic properties outside historic districts, and lots in a floodway or 100-year floodplain.
Grants and Financing: Colorado Will Help Pay
HB24-1152 came with about $13 million: $5M in fee-reduction grants and $8M for ADU financing. The ADU Grant Program (ADUG) launched August 2025 through jurisdictions certified as "ADU Supportive" — Round 3 applications run August 3–31, 2026 — and certified-jurisdiction homeowners can access ADU financing through CHFA. Check whether your city is certified, and find the state's ADU Toolkit, on DOLA's ADU page.
Practical path: confirm your city is a subject jurisdiction → pull its objective ADU standards (post-June-2025 versions) → pre-check the exempt-parcel tests (water/sewer, floodplain) → budget for impact fees even though hearings are gone → if your city is ADU Supportive, time your application to a grant round.
Sources
- HB24-1152 — Colorado General Assembly bill page and signed act
- Colorado DOLA — Accessory Dwelling Units program (grants, certification, toolkit)
Statutes and agency guidance last reviewed July 2026.
How Colorado Compares to Other States
Below is a comparison of Colorado with five states that have similar ADU-friendliness scores. This comparison helps illustrate where Colorado stands nationally.
| State | Score | Statewide Law | Parking Req? | Owner Occ? | Ease |
|---|---|---|---|---|---|
| Colorado (CO) | 83 | Yes | No | No | Easy |
| Arkansas (AR) | 83 | Yes | No | No | Easy |
| Connecticut (CT) | 83 | Yes | No | No | Easy |
| Massachusetts (MA) | 85 | Yes | No | No | Easy |
| Arizona (AZ) | 86 | Yes | No | No | Easy |
| Maine (ME) | 80 | Yes | No | No | Easy |
Frequently Asked Questions About ADUs in Colorado
Can I build an ADU in Colorado?
Yes, ADUs are allowed in Colorado. Colorado has a statewide ADU law that requires local jurisdictions to permit ADUs on residential lots. This means your city cannot outright ban ADUs. The ease of building is rated "Easy" with a friendliness score of 83/100.
Do I need to live on the property to have an ADU in Colorado?
No, Colorado does not require owner occupancy for ADUs. You can rent out both the main house and the ADU, which maximizes rental income potential.
How big can an ADU be in Colorado?
Colorado does not set a statewide maximum ADU size — this is determined by your local jurisdiction. Common local limits range from 600 to 1,200 square feet. Check your city's zoning code for the specific maximum.
Do I need extra parking for an ADU in Colorado?
No — Colorado does not require additional parking for ADUs. This is a significant advantage, as parking requirements are often the biggest barrier to ADU construction on smaller lots.
How long does it take to get an ADU permit in Colorado?
The permitting timeline in Colorado is: 90 days max. The statewide law sets maximum review periods that cities must comply with.
Does Colorado have a statewide ADU law?
Yes. State law sets the floor that Colorado cities must meet: no statewide size cap, no owner-occupancy mandate, no added parking, with permitting handled as: 90 days max. Cities can be more permissive than the state baseline but generally not stricter.
Check ADU Rules for Your City
Use our ADU regulations lookup tool to find the specific rules for your city in Colorado, or browse all 50 states to compare ADU regulations across the country.