San Mateo County, CA Home Business: Zoning Restrictions (2026)

Home-based businesses in the unincorporated County are regulated as 'home occupations' under the County Zoning Regulations, historically codified at Section 6102.46 and now carried into the reorganized County Ordinance Code (Title 8 - Development Code, adopted by the Board of Supervisors on October 8, 2024). According to the County Planning and Building Department, a home occupation is permitted in the RE, RH, R-1, R-2, R-3, R-3-A, RM, RM-CZ and PAD zoning districts when it is customary and incidental to the residential use and all conditions are met. Those conditions are: no retail business of any sort is involved; no stock in trade is kept or commodity sold on the premises (except articles made on-site); no person who is not a resident of the premises is employed in the home occupation; an area not larger than one-fourth (1/4) of the floor area of the ground floor of the dwelling is devoted to the occupation; no internal or external alterations are made and the entrance to the space used is from within the building; and no display pertaining to the occupation is visible from the street. The intent is to keep the use unobtrusive so the neighborhood retains its residential character. Uses that generate customer traffic, outdoor storage, noise, or that require employees or retail sales generally do not qualify and would need a different land-use approval.