ADU rules in Modesto, CA — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Modesto Municipal Code Article 5 (sections 10-4.501 to 10-4.512) permits ADUs ministerially on lots with a single-family or duplex dwelling, capping detached units at 1,200 sq ft and 16 ft in height (18 ft near major transit), with 4 ft side and rear setbacks. Standards mirror Govt Code section 65852.2.
Modesto's ADU article was adopted by Ord. No. 3762-C.S. (effective May 11, 2023), which repealed former section 10-4.115 and replaced it with sections 10-4.501 through 10-4.512. Per section 10-4.505, ADUs are allowed on lots with an existing or proposed single-family dwelling or duplex. Section 10-4.506 caps detached ADUs at 1,200 sq ft and attached ADUs at 50% of the primary dwelling or 800 sq ft, whichever is greater. Section 10-4.507 limits detached ADU height to 16 ft, or 18 ft when within one-half mile walking distance of a major transit stop, and allows attached ADUs up to 25 ft or the underlying zone limit. Detached ADUs must observe a minimum 4 ft side and rear setback. The Modesto regulations implement California Government Code section 65852.2, which preempts local ADU restrictions and requires ministerial (over-the-counter) approval within 60 days of a complete application.
An ADU built without a permit, or one that exceeds height/size limits, is subject to code enforcement under Title 1 Chapter 6, which authorizes administrative citations, stop-work orders, and recordation of a notice of violation. Unpermitted structures may have to be brought into compliance or removed at the owner's expense.
Other ordinances people look up for this city. Green dot = verified primary-source excerpt.
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