Council studies ADU rule changes, pre‑approved plans and duplex options to expand housing

Becky Smith, the city’s director of planning and development, told the City Council at a study session that council had asked staff in 2025 to evaluate accessory dwelling unit (ADU) regulations and other small‑scale density strategies, including whether to allow shipping‑container ("ConX") conversions and duplexes as a use by right in single‑family zones.

Smith said the current Unified Development Ordinance allows ADUs in RS1 and RS2 but limits detached ADUs to a maximum of 750 square feet, one bedroom and requires an owner to live on the site. She told council that "the UDO expressly prohibits ConX boxes in residential neighborhoods" and that allowing them would require code amendments and additional engineering and inspections because container conversions are not covered by federal HUD or the Colorado Division of Housing certification paths.

The presentation emphasized three alternatives: (1) allowing engineered shipping‑container conversions with accompanying design standards; (2) encouraging factory‑built, pre‑certified ADUs that have streamlined inspections; and (3) creating pre‑approved ADU plan sets the city could make available to homeowners to reduce design time and cost. On factory‑built options, Smith said many models approved by HUD or the state Department of Housing have an easier permitting pathway.

Council members largely saw value in lowering costs and permitting friction. Council Member Noiki described building an ADU for his mother and said his project’s "low end was about $125,000," arguing that factory‑built options or pre‑approved plans could reduce those barriers. Several councilors, including Condo and Goff, urged caution about ConX boxes because conversions often require extensive engineering and can be more expensive than anticipated; others favored jurisdiction‑approved plan sets as a way to lower homeowner costs without immediate city expense.

Members also discussed allowing duplexes in RS1/RS2 to increase the "missing middle" supply but repeatedly raised concerns about infrastructure and neighborhood character. Smith said the city’s integrated water resources modeling indicates the 2020 plan included projections that were not realized and that staff is updating the plan; she told council there are "555 units that weren't actually realized" in earlier planning estimates and staff will return with refined infrastructure capacity information.

By the end of the discussion multiple council members expressed support for directing staff to research factory‑built ADUs and assemble a list of pre‑certified structures and to investigate pre‑approved plan options (with any city‑funded plan program to be considered as a future budget request). Council did not amend the UDO at the meeting and no formal vote on code changes was taken.

The next steps Smith outlined include staff research on certified prefab ADU models, updating the integrated water resources plan to clarify capacity, and returning to council with options for pre‑approved plans and draft code language if council directs amendments.