South San Francisco, CA Short-Term Rentals: Primary-Residence-Only Rule (2026)

Unlike some California jurisdictions, unincorporated San Mateo County does not impose a primary-residence requirement on Coastal Zone short-term rentals. Nothing in Zoning Regulations Section 6401.3 conditions an STR permit on the home being the owner's principal dwelling, and the ordinance expressly contemplates whole-home rentals: the definition of 'short-term rental' covers a 'single-family dwelling unit or multifamily unit, or portion(s) thereof,' and an 'owner' includes a fee-title holder or a lessee of at least 30 days. The County instead controls intensity of use through other tools - principally the 180-nights-per-calendar-year cap under Section 6401.3(2)(c), the occupancy and parking limits, and the local-contact requirement - rather than by mandating owner occupancy. Importantly, the night cap contains an incentive for owner presence: any night the owner is present at the property does not count against the 180-night limit, but that is an exception, not a requirement to occupy. The ordinance does require the applicant to be an owner or an authorized lessee/representative (Section 6401.3(4)), and it prohibits using deed-restricted affordable housing or second units (ADUs) as STRs. Owners should still confirm that no separate HOA covenant or lease restricts short-term rentals, since a County permit does not override private agreements (Section 6401.3(2)(a)).