Sunnyvale processes ADU permits ministerially under Sunnyvale Municipal Code Title 19 (Zoning) and California Government Code 65852.2. Sunnyvale was one of the earliest California cities to adopt by-right ADU regulations (2017) and consistently rates as one of the most permissive Silicon Valley jurisdictions. State law requires action within 60 days of a complete application.
Sunnyvale's ADU regulations live in Title 19 (Zoning) of the Sunnyvale Municipal Code, originally streamlined in 2017 (one of California's earliest progressive by-right adopters) and updated repeatedly to track state law amendments to California Government Code 65852.2 - including SB 9 (2021), AB 587, and AB 1033 (2023, allowing condominium-style ADU sales). Review is ministerial under Gov. Code 65852.2(b)(1): no Planning Commission hearing, no public notice, and no discretionary design review beyond objective standards. Applications go through Sunnyvale's One Stop Permit Center / Online Permit Center maintained by the Community Development Department. Required submittals: site plan, floor plans, elevations, Title 24 energy compliance forms, structural plans, and a stormwater checklist. State law (Gov. Code 65852.2(b)(1)) requires Sunnyvale to approve, deny, or request corrections within 60 days of a complete submittal. Sunnyvale allows one ADU plus one JADU on every Single Family Home (SFH) lot in R-0, R-1, and R-2 districts (up to 3 units total). Maximum size: detached ADU up to 1,200 sq ft, attached ADU up to 50% of primary or 1,200 sq ft, JADU up to 500 sq ft inside the primary dwelling. State default 4 ft side and rear setbacks apply. Sunnyvale also offers pre-approved (pre-reviewed) ADU plans under Assembly Bill 434 (Gov. Code 65852.26) that further accelerate permitting.
Building an ADU without a permit violates SMC Title 16 (Building) and Title 19 (Zoning). Sunnyvale Code Enforcement can issue stop-work orders, administrative citations starting at $100 per violation (SMC 1.04), double permit fees on legalization, and orders to remove unpermitted structures. Unpermitted ADUs commonly block sale and refinancing of the property.
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