Yavapai County adopts accessory‑dwelling rules to implement state law, adds sewer adequacy and a 1,000‑sq‑ft cap

The Yavapai County Board of Supervisors on Nov. 19 adopted a text amendment to the county zoning ordinance to implement recent state legislation that requires counties to allow accessory dwelling units (ADUs). The change updates definitions, clarifies permitted uses and establishes development standards for attached and detached ADUs.

Susan Hebert, planner with Development Services, told the Board that under the state‑mandated baseline an accessory dwelling unit is a self‑contained living unit on the same lot as a single‑family dwelling; counties must adopt standards by Jan. 1, 2026 or ADUs would otherwise be allowed without local rules. Hebert explained the county’s recommended approach would preserve applicable building, environmental and public‑safety codes and add local clarifications where permitted by statute (for example, a county may set a larger maximum square footage than the state minimum).

The Board debated size limits and public concerns. Randy Garrison, planning commission member, said the commission supported a larger allowance in some cases but warned that a 1,500‑sq‑ft cap “is a very large structure” that could begin to resemble a primary residence rather than an accessory unit. Several supervisors asked about septic, water availability and parking impacts.

After discussion the Board adopted the amendment with additional stipulations requested in the hearing: staff inserted the word “adequate” to require sewer or septic systems to have adequate capacity before an ADU is built, and the Board set the standard maximum ADU size at 1,000 square feet for typical parcels.

What this means: under the new ordinance, one attached and one detached ADU are permitted on properties that allow single‑family dwellings; an additional detached ADU (with larger size options) remains possible on parcels of one acre or more subject to county standards and environmental requirements. ADUs are exempt from additional parking requirements under state law but the county requires replacement parking if construction removes required spaces for the primary residence. Setbacks of 5 feet for side/rear yards apply to ADUs, and building permits and environmental reviews (including septic/water capacity) remain required.

Why it matters: supervisors said the change balances state law with county safeguards on infrastructure capacity and public health. Several board members said they expect to revisit ADU rules during the comprehensive zoning update.

Next steps: Development Services will publish the amended ordinance and integrate the new ADU standards into permit and address‑assignment procedures; environmental and septic capacity reviews will be applied at the permit stage.