San Mateo County, CA Home Business: Zoning & Home Occupation Permits (2026)
Key Facts
- Floor area limit
- 1/4 of ground floor
- Employees allowed
- residents only
- Sign limit
- 2 sq ft, unlit
- Permitted zones
- R-E, R-1 (as of right)
Summary
Unincorporated San Mateo County allows home occupations by right in residential zones like R-1 and R-E, but caps them at a quarter of the ground floor with no retail sales or outside employees.
Customary, incidental home occupations conducted within a dwelling, provided that no retail business of any sort is involved; no stock in trade is kept, or commodity sold, except for the sale of commodities made on the premises; no person not a resident of the premises is employed; and an area not larger than one-fourth (1/4) of the floor area of the ground floor of the dwelling is devoted to such home occupation; provided, however, that such home occupation shall not require internal or external alterations...and that no display pertaining to such occupation be visible from the street.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 47).
Full Breakdown
County zoning permits home occupations as of right in the R-E and R-1 residential districts. The use must stay incidental: no retail business of any kind, no stock in trade sold except items made on the premises, no employee who doesn't live at the dwelling, and no more than one-fourth of the ground floor devoted to the activity. No internal or external alterations are allowed, the workspace must be entered from inside the home, and nothing tied to the business may be visible from the street.
Violations & Fines
Exceeding the floor-area cap, employing a non-resident, making exterior alterations, or displaying business activity visible from the street takes the use outside the permitted definition and can bring zoning code enforcement.
Frequently Asked Questions
Can I hire outside help for a home business in unincorporated San Mateo County?
Can I put up a sign for my home business?
Sources & Official References
Other rules in San Mateo County
How San Mateo County compares: Easiest Cities to Run a Home Business·California rules heatmap·Compare San Mateo County to another location·View the California home business overview
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