ADU rules in Pitkin County, CO — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Pitkin County does not use the term 'ADU' as a primary regulatory category. Instead, the Pitkin County Land Use Code (LUC) recognizes Caretaker Dwelling Units (CDUs) and Employee Dwelling Units (EDUs), both of which are deed-restricted accessory dwellings tied to local-employee occupancy under the Aspen/Pitkin County Housing Authority (APCHA) framework. A CDU is a permitted accessory use in most rural and residential zones (RS-160, RS-35, RS-30, RS-20, AR-10, AR-2, R-30, R-15, R-15A, R-6) when attached to a single-family principal dwelling and the lot meets the minimum lot area for one dwelling unit in that zone (LUC Sec. 4-30-50(e)(1)). Detached CDUs and CDUs on substandard lots require Special Review (LUC Sec. 4-30-50(e)(2)). Maximum size is 1,000 net livable square feet on lots 30,000 sq ft or larger and 700 net livable square feet on lots smaller than 30,000 sq ft. The CDU floor area counts against the parcel's total allowed floor area. A deed restriction must be recorded limiting occupancy to no more than two adults plus related children who qualify as community employees under APCHA guidelines, or members of the owner's immediate family, with rentals (if rented) of at least six months. EDUs are a separate category up to 1,500 net livable square feet, also deed-restricted to APCHA-qualified residents under LUC Sec. 6-30-40(d). HB24-1152 (Colorado's 2024 statewide ADU mandate) does not apply: Pitkin County and the City of Aspen are not within any of Colorado's five MPOs (DRCOG, NFRMPO, PPACG, GVMPO, PACOG), so the county is not a 'subject jurisdiction' and retains full discretion over accessory dwelling rules under CRS Title 30 county powers.
Pitkin County's accessory-dwelling regime is set out in the Pitkin County Land Use Code (LUC), particularly Chapter 4 (Permitted Uses), Chapter 5 (Dimensional Requirements), Chapter 6 (Growth Management Quota System), and Chapter 11 (Definitions). Chapter 11 defines a Caretaker Dwelling Unit (CDU) as 'a separate, accessory dwelling that is deed restricted to occupancy by qualified residents, as defined in the employee housing guidelines, and is subject to the restrictions of Sec. 4-30-50(e) of this Land Use Code,' and an Employee Dwelling Unit (EDU) as 'a separate, accessory dwelling unit of less than one thousand five hundred (1,500) net livable square feet attached to, within, or detached from a principal dwelling unit situated on the same parcel,' deed-restricted to APCHA-qualified residents and subject to LUC Sec. 6-30-40(d). Under LUC Sec. 4-30-50(e)(1), one CDU is a permitted accessory use in the RS-160, RS-35, RS-30, RS-20, AR-10, AR-2, R-30, R-15, R-15A, and R-6 zone districts, provided it is attached to a single-family principal dwelling, the lot meets the underlying zone's minimum lot area for one dwelling unit per Table 5-1, the CDU does not exceed 1,000 net livable square feet on lots of 30,000 sq ft or more (or 700 net livable sq ft on smaller lots), the CDU floor area is counted within the parcel's total allowed floor area, and two off-street parking spaces are provided. Sec. 4-30-50(e)(2) requires Special Review approval for any CDU located in the LIR-35, VR, B-2, VC, P-I, or T zone districts, located on a substandard lot, or detached from the principal dwelling. The deed restriction recorded under Sec. 4-30-50(e)(1)(f) must run with the land and provide that the CDU shall not be required to be rented, shall not be sold or conveyed separately from the parent parcel regardless of ownership form, shall be limited to occupancy by no more than two adults and related children who qualify as APCHA-approved community employees or who are members of the owner's immediate family, and if rented shall be rented for terms not less than six months. Under Sec. 6-30-40(c), one CDU may be exempted from the Growth Management Quota System on any lot or parcel located in a zone district where the CDU is allowed (by right, by special review, or as part of a master plan), including lots that are substandard for the underlying zone's minimum parcel size. The CDU restriction may be removed under Sec. 4-30-50(e)(1)(g) only with Community Development Director approval and only if the dwelling is removed or modified so it is no longer capable of being occupied as a dwelling unit. CDUs created under Sec. 4-30-50(e) cannot be used as employee-housing mitigation for separate development requirements. Inside the City of Aspen, the City of Aspen Land Use Code controls (Aspen has its own ADU and resident-occupied affordable housing program, and Aspen has been actively reviewing 'Lodging' overlays and short-term-rental rules separately). The Town of Snowmass Village uses its own Town Municipal Code. Building permits, OWTS (septic) approval through Pitkin County Environmental Health, and Wildfire Hazard Area review may be required before a CDU can be constructed. Pitkin County is part of the Intermountain Transportation Planning Region and is not located within any Colorado Metropolitan Planning Organization, so HB24-1152 (effective June 30, 2025 for 'subject jurisdictions') does not preempt these local rules.
Constructing or occupying a CDU or EDU without recording the required deed restriction, without obtaining the underlying building and zoning permits, or without OWTS approval where applicable violates the Pitkin County Land Use Code and the building code adopted by the county. Renting a CDU for less than six months, renting it to occupants who are neither APCHA-qualified community employees nor immediate family of the owner, conveying the CDU separately from the principal parcel, or exceeding the two-adult occupancy cap violates the recorded deed restriction and is enforceable both as a code violation and as a contractual restriction running with the land. APCHA conducts compliance audits and can pursue civil enforcement, including loss of qualification, fines, and forced sale or correction. Pitkin County Community Development enforces zoning violations through stop-work orders, denial of certificates of occupancy, and abatement under CRS Title 30, Article 28, with daily civil penalties available through county court. Removing the CDU deed restriction without Community Development Director approval, or failing to physically remove or modify the unit so it can no longer be occupied as a dwelling when the restriction is lifted, is a separate violation. Detached CDUs constructed without Special Review under LUC Sec. 4-30-50(e)(2), CDUs that exceed 1,000 net livable square feet on qualifying lots or 700 net livable square feet on smaller lots, and CDUs that exceed the parcel's total allowed floor area are subject to enforcement and may have to be reduced in size or demolished. Listing a CDU on a short-term rental platform (Airbnb, VRBO) violates both the six-month minimum lease requirement and Pitkin County's separate vacation-rental licensing rules. Inside Aspen and Snowmass Village, the respective municipal codes apply and town enforcement (rather than county enforcement) controls.
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