Fremont, CA Accessory Structures: ADU Rules (2026)

005 implements the state ADU statutes through ministerial review: the city must deem an application complete or incomplete within 15 business days and issue the permit within 60 days of a complete application if an existing single-family or multifamily dwelling is already on the lot. One ADU is allowed per single-family lot (an ADU and a junior ADU, or JADU, may share the same primary dwelling). New detached ADUs are capped at 1,200 square feet of interior livable space; attached ADUs built from new floor area are capped at 1,000 square feet.

An ADU converted from existing floor area faces no size or height cap at all. Height limits for new construction are tiered: an ADU attached to a single-family home is capped at 30 feet or the underlying zoning district limit, whichever is lower; a detached single-family ADU is capped at 16 feet (18 feet if within a half-mile walk of a major transit stop or high-quality transit corridor, plus two more feet to match a pitched roofline). Setbacks for new floor area are four feet on the side and rear, with the ADU otherwise following the primary dwelling's front setback.

No setback at all applies to an ADU built within existing living area or an existing accessory structure. The code bars rooftop decks on ADUs outright, does not require owner occupancy for either unit, waives any additional parking requirement, and bars fire-sprinkler mandates that would not otherwise apply to the primary dwelling. JADUs are capped at 500 square feet within the walls of a single-family home, require a recorded deed restriction against separate sale, and need owner occupancy only when sanitation facilities are shared with the main house. 300.