Gilroy, CA Accessory Structures: ADU Rules (2026)

Article LIV of the Gilroy City Code, adopted to implement California Government Code Section 66310 et seq., governs accessory dwelling units citywide. Section 30.54.30(a) allows an ADU on any residential parcel in any zoning district that permits residential or mixed-use development and that has an existing or proposed primary single-family dwelling. Size is capped under subsection (d): a detached ADU cannot exceed 1,000 square feet of floor area, while an attached ADU is capped at 50 percent of the existing primary dwelling's gross floor area (garage area excluded), though an 850-square-foot one-bedroom or 1,000-square-foot two-or-more-bedroom unit is allowed regardless.

Height is set in subsection (e): 16 feet for a detached ADU, rising to 18 feet, and up to 20 feet to match the primary dwelling's roof pitch, for units within one-half mile of a major transit stop or high-quality transit corridor; an ADU built above a detached garage may reach 24 feet, and one attached to the primary dwelling is limited to the underlying zoning district's height limit. Setbacks under subsection (f) require 4 feet from side and rear lot lines for a newly constructed detached ADU, with no additional setback required when converting an existing permitted accessory structure or garage in place.

Section 30.54.20 requires ministerial approval, meaning no discretionary review or public hearing, within 60 days of a complete application, and bars conditioning approval on correcting preexisting nonconforming zoning. Parking under § 30.54.30(g) requires one added space for a newly built ADU, waived entirely for conversions of existing space, units within a half-mile of transit, historic districts, or where street parking permits are unavailable to the ADU's occupant.