San Marcos ADU Regulations

• ✓ADU FAQ available in English and Spanish
• ✓Homeowners Guide under Building Code Compliance ties to ADU development guidance
• ✓Development Services office hours include alternating Fridays
• ✓Junior ADU pathway addressed alongside ADUs in city FAQs

City materials define ADU as a full independent dwelling. JADU up to 500 sq ft within an existing dwelling. See the Planning ADU FAQ and municipal code for exact maxima.

State guarantee: California requires every city to allow at least an 800 sq ft ADU exempt from local lot coverage, FAR, and front-setback rules.

Height baseline: 16 ft for detached, rising to 18 ft within ½ mile of major transit. Attached ADUs follow the primary home, capped at 25 ft.

Setbacks, height, and parking per city zoning. Planning Division confirms parcel-specific standards.

Building Application Packet referenced for ADU projects. Permit lookup via the city eTRAKiT portal.

State backstop: A complete ADU permit must receive a decision in 60 business days. If the city stalls past 30 business days, AB 253 lets you hire a certified private plan checker to force a 10-business-day decision.

Fees per city fee schedules and impact-fee rules at permit issuance. Confirm with Development Services.

SB 543: No impact fees on ADUs ≤750 sq ft. Above 750 sq ft, fees scale to the ratio of ADU size vs the main home.

Visit the official San Marcos ADU page (link in hero) for current eligibility and downloads.

Standard ADUs in San Marcos: no owner-occupancy required (made permanent in 2023).

JADUs: limited to 500 sq ft of interior livable space within an existing single-family home. Owner occupancy is required only when sanitation facilities are shared with the main house. JADUs cannot be used as short-term rentals (AB 1154 / SB 543).