ADU debate centers on density, utility impacts and whether detached units can be limited

Accessory dwelling units (ADUs) drew a prolonged discussion at the Nov. 21 Grantsville Planning Commission meeting, with members and public commenters divided over how to allow ADUs without overburdening infrastructure or enabling developers to increase density through code workarounds.

Gary (S2) told the commission his experience with increased density elsewhere warned of doubling sewer, water and traffic impacts when many homes add separate backyard units. Commissioners asked whether detached ADUs should be allowed only on larger lots, whether ADUs should be built at the same time as the primary residence to avoid later unplanned density, and whether separate meters and impact fees should be allowed. Several members noted state law limits the city's ability to collect impact fees for ADUs and that separate meters can create incentives to separate and sell an accessory unit later.

Staff (S6) and legal/administrative commenters noted examples from other cities: Farmington requires a 10,000-square-foot minimum for detached ADUs and includes owner-occupancy limits and minimum occupancy timelines before a detached unit can be severed. Commissioners flagged edge cases — for example, long-term owner illness could unintentionally void an owner-occupancy requirement — and asked staff to research workable guardrails such as minimum lot sizes, parking requirements (multiple commissioners recommended two additional parking spaces per ADU), setback clarifications so two detached homes cannot end up 10 feet apart on neighboring lots, and whether separate meter rules would legally permit impact-fee collection.

No final policy changes were approved for ADUs at the meeting; staff was asked to research statutory limits on impact fees and meter separations, consider minimum lot sizes and setback language for detached units, and return with options that balance added housing with infrastructure and emergency-access safety.