ADU rules in Golden

A detached backyard ADU is allowed. Section 18.28.04.05(1) allows accessory dwelling units in conjunction with all single-household and two-household dwellings in the residential zone districts, listing RE, R1, R1A, R2, R3 and PUD, and the code defines a residential accessory dwelling unit to include one "in a separate accessory structure on the same lot as the principal dwelling." Only one ADU is allowed per single-household or two-household dwelling unit, and the ADU can only go on a lot actually used as a one- or two-household dwelling. A detached ADU must use exterior wall materials, window types, trim, roofing material and roof pitch similar to the main house, and it takes its height, setback and lot coverage limits from the standards that apply to the principal dwelling (the form type in Chapter 18.29 inside a form zone overlay, or the legacy standards in Chapter 18.28 Appendix A elsewhere).

Attached and internal ADUs are allowed on the same footing as detached ones. The definition in § 18.04.020 covers a secondary dwelling unit "either within a structure containing an existing single-household detached dwelling, or in a separate accessory structure," and § 18.28.04.05(5)(c) sets a specific size rule for an ADU "enclosed entirely within a building containing an existing single-household or two-household dwelling unit." A basement conversion is the common case: the city's ADU page notes that new detached ADU construction requires fire sprinklers in the new space but that a basement converted to living space is the exception. Additions that create an ADU still have to meet the form type or bulk standards that apply to the property.

Section 18.28.04.05(5) sets three size rules. If the principal single-household or two-household dwelling has 1,000 square feet or more of living space, the ADU may be no larger than 50 percent of that living space or 800 square feet, whichever is smaller. If the principal dwelling has less than 1,000 square feet of living space, the ADU is capped at 500 square feet. No ADU may be smaller than 200 square feet, and garage, porch and similar areas are excluded from the floor area calculation. An ADU built entirely inside a building that already contains a single-household or two-household dwelling may be no larger than any existing dwelling unit in that building. There is no separate ADU height limit: § 18.28.04.05(2) subjects ADUs to the same development standards as the principal dwelling, so height, setbacks and lot coverage come from Chapter 18.29 (form types) or the Chapter 18.28 Appendix A legacy standards.

Golden's operative code still requires it, and the city still advertises it. Section 18.28.04.05(8) says the property owner of record, shown by title records and evidenced by voter registration, vehicle registration or similar means, must occupy either the principal dwelling or the ADU; the director may waive this for temporary absences if the owner has occupied one of the units for at least two years and submits proof. Section 18.28.04.05(13) goes further and requires the owner to record a deed restriction before a building permit issues, stating that the ADU's certificate of occupancy is in effect only so long as the owner of record occupies the principal dwelling or the ADU. The city's ADU page, live on 2026-07-31, repeats that the owner on record must occupy one of the units as their primary residence and that proof of primary residence is required. Colorado's HB24-1152 bars a subject jurisdiction from requiring owner occupancy after June 30, 2025 (it may only ask the owner to show they reside on the parcel at the time of application), and the Department of Local Affairs lists Golden as a subject jurisdiction, so this requirement is very likely preempted; see caveats.

Section 18.28.04.05(4) requires one on-site parking space for an ADU, in addition to the parking required for the principal dwelling under Chapter 18.36. The space may be in tandem with other required spaces, for example stacked in an existing driveway, but it has to be identified on a site plan. Golden does not publish an ADU parking waiver. HB24-1152 bars a subject jurisdiction from requiring the construction of a new off-street space for an ADU, while still allowing it to require that an existing driveway, garage or tandem space be designated for the ADU, so the designation part of Golden's rule survives state law but a demand to build a new space on a lot that already has off-street parking likely does not.

No public hearing and no special use permit. ADUs sit in Division IV of Chapter 18.28, Temporary and Accessory Uses, rather than in the use table, so they carry no P, L or S designation and are simply allowed where § 18.28.04.05(1) says they are. Review is administrative: under § 18.10.020(1) administrative approvals and permits are issued by the director on a finding of code compliance and no public hearing is required. A new detached ADU is a new building, so it needs a Site Development Plan, or a Form Zone Site Development Plan (SDP-FZ) if the lot carries a form zone overlay, both decided by the director per table 18.10.020.1, plus a building permit. Before the building permit issues the owner must record the deed restriction required by § 18.28.04.05(13), and the ADU's certificate of occupancy cannot issue until the principal dwelling has one.

Golden does not prohibit renting an ADU for 30 days or more, but the required deed restriction ties the ADU's certificate of occupancy to continued owner occupancy of either unit, so the practical pattern is owner in one unit and tenant in the other, and the ADU can never be sold off separately from the main house. Renting for less than 30 days is a short-term rental and needs a temporary lodging license under Chapter 18.22, issued administratively by the director. Under § 18.22.080 the licensee must be the fee owner of record, must occupy the licensed premises or the lot for at least ten months of every calendar year, must hold a City of Golden sales and use tax license, and is capped at four adults plus their dependents. Critically for ADU owners, § 18.22.080(d) says that where a lot holds more than one legal dwelling unit, including an ADU, only one dwelling unit on that lot may be licensed as a short-term rental. Licenses run $200 for two years per the city's STR page. In commercial districts the equivalent license is a tourist home under § 18.22.090, which has no owner-occupancy or primary-residence requirement.