Costa Mesa, CA Accessory Structures: ADU Rental Restrictions (2026)

' The restriction applies regardless of the zone the ADU sits in, whether the unit was newly constructed, converted from an existing accessory structure, or built as part of a new single-family or multifamily development, and it applies on top of the section's other occupancy and permitting rules, including the requirement that ADUs and Junior ADUs cannot be sold or conveyed separately from the primary residence. Because the 31-day threshold matches the point at which California law treats a rental as a longer-term tenancy rather than a transient occupancy, the effect is to keep ADUs and JADUs out of the nightly and weekly vacation-rental market entirely, reserving them for month-plus tenants only.

The prohibition sits inside the broader ADU development standards adopted and amended most recently by Ordinance 2025-07 (October 21, 2025), and applies citywide to every ADU and JADU permitted under section 13-35, not just newly built ones. Property owners who plan to use an ADU as a guest house or long-term rental face no restriction beyond the 31-day floor; the section imposes no cap on rent amount, tenant screening, or number of renters, focused solely on rental duration.