Sonoma County, CA Accessory Structures: ADU Rental Restrictions (2026)

Ordinance No. 6544, adopted December 9, 2025, repealed Section 26-88-060, so that old ADU section now reads "Reserved" in the Code. The ADU standards moved into Zoning Code Section 26-24-020, which implements Title 7, Chapter 13 of the California Government Code (Sections 66310-66341). Subsection C holds the two use restrictions that matter to owners and tenants.

Ownership and rental: an ADU can be rented, but it cannot be sold or otherwise conveyed separately from the primary residence unless State law specifically provides otherwise. Duration of tenancy: an ADU cannot be rented for periods of thirty days or less, so a stay must run at least thirty-one days. A junior ADU (JADU), which is capped at 500 square feet and sits entirely inside a single-family residence, follows a parallel rule in Section 26-24-150(C): it can be rented but not sold separately from the single-family residence.

The rental right comes with a ministerial permit path. A complete ADU application that meets the section's standards is approved without discretionary review or a hearing. When a primary dwelling already exists on the lot, the department has sixty days from a complete application to approve or deny it, and a denial must come with a full set of comments listing each defective item and how the applicant can fix it. The primary permit is a building permit, with grading, well, septic and sewer permits added where they apply.

Lot capacity shapes what can be rented. A lot with a single-family dwelling can hold two ADUs plus one JADU, and an ADU there can reach 1,200 square feet. A lot with an existing multifamily dwelling can add up to eight detached or attached new-construction ADUs, capped at the number of existing primary units. Additional parking is not required for an ADU, and no minimum lot size applies. A certificate of occupancy for an ADU cannot be issued before the one for the primary residence.