ADU rules in San Marcos, CA — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
San Marcos allows one ADU plus one JADU per single-family lot per SMMC Chapter 20.410.060. One-bedroom ADUs up to 850 sq ft, two-bedroom up to 1,000 sq ft. ADUs generally cannot be in the front yard. A soils report is required over 500 sq ft.
San Marcos permits ADUs under SMMC Chapter 20.410.060 consistent with CA Government Code Section 65852.2. Single-family lots may have one ADU and one JADU (converted from existing space, up to 500 sq ft, owner-occupancy required). Maximum sizes: 850 sq ft (1BR), 1,000 sq ft (2+BR), attached units limited to 50% of main home. ADUs generally cannot be in the front yard. A soils report is required for ADUs over 500 sq ft. Multifamily lots may have up to 2 detached ADUs. Mello-Roos CFD fees may apply, adding 3-4 months for ADUs over 749 sq ft. ADUs may not be sold separately. Rentals must be 30+ days.
Unpermitted ADU construction subject to enforcement. Short-term rental of ADUs is a zoning violation. Separate sale not permitted.
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Side-by-side rule comparisons with other cities in San Diego County.
See how other cities in San Diego County handle adu rules.
See how San Marcos's adu rules rules stack up against other locations.
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