California ADU rules · Santa Clara County
Can I Build an ADU in Gilroy?
Yes — you can build an ADU in Gilroy. California's statewide ADU law requires every city, including Gilroy, to approve a qualifying accessory dwelling unit by right, plus a junior ADU (JADU) on a single-family lot. What varies city to city are the local specifics below.
Can you build one?
ADUs allowed
CA state lawYes — by right
ADUs and JADUs are allowed by right in all residential and mixed-use zones; ministerial approval, no hearing.
Units on a single-family lot
CA state law1 ADU + 1 JADU
At least one ADU and one JADU per single-family lot (a conversion ADU may also be possible).
Units on a multifamily lot
CA state lawConversion ADUs (≥1, up to 25% of units) + up to 8 detached
Conversions of non-livable space (at least 1, or up to 25% of existing units) plus up to 8 detached ADUs on a lot with existing multifamily — never exceeding the number of existing units. JADUs are single-family only.
Junior ADU (JADU)
CA state lawAllowed
Up to 500 sq ft, within the walls of an existing single-family home (single-family lots only).
Size & height
Max detached ADU size
Local rule1,000 sq ft
Local maximum for detached ADUs is 1,000 sq ft, which is lower than the state default cap of 1,200 sq ft.
Max attached ADU size
Local rule50% of primary dwelling’s gross floor area (excluding garage), but must allow at least 850 sq ft (1-bedroom) or 1,000 sq ft (2+ bedrooms)
Local rule mirrors state minimums but clarifies 50% cap unless state minimums are higher.
Guaranteed minimum size
CA state law800 sq ft
An 800 sq ft ADU must be allowed regardless of FAR/lot-coverage caps; a city also cannot cap an attached ADU below 850 sq ft (1,000 for 2+ bedrooms).
Max JADU size
CA state law500 sq ft
Max height
CA state law16 ft
16 ft baseline; cities must allow 18 ft within ½ mi of a major transit stop or where the primary dwelling is two-story, and 20 ft on a lot with a multistory multifamily building.
Setbacks
Side setback
CA state law4 ft
A city cannot require more than 4 ft side or rear setback; conversions of existing structures are exempt.
Rear setback
CA state law4 ft
Front setback
Local ruleADUs must not encroach on required front yard unless it would preclude an 800 sq ft ADU with 4-ft setbacks
Local code clarifies front setback encroachment only allowed to guarantee state-minimum ADU.
Separation from main house
CA state lawNone required
No statewide separation requirement between the ADU and the primary dwelling.
Parking
Parking required
Local ruleUp to 1 space
1 space per new ADU unless exempt; exemptions closely follow state but are locally codified.
Transit parking exemption
CA state lawYes — no parking required near transit & for conversions
No parking may be required within ½ mi walking distance of transit, in a historic district, for an ADU within an existing structure, within one block of car-share, or in certain permit-parking areas.
Garage-conversion replacement parking
Local ruleNot required
No replacement parking required when garage is converted to ADU.
Approval, timeline & cost
Approval path
CA state lawMinisterial (by right)
No public hearing or discretionary design review for a qualifying ADU.
Approval timeline
CA state law60 days
The agency must act within 60 days of a complete application — and the ADU is deemed approved if it does not.
Owner-occupancy
Local ruleOnly for a JADU
No owner-occupancy for ADUs; JADUs may require owner-occupancy per state law.
Impact-fee waiver
CA state lawWaived under 750 sq ft
An ADU of 750 sq ft or less pays no impact fees (the 750 sq ft threshold itself is exempt under § 66311.5); larger ADUs pay fees proportional to the primary dwelling. JADUs (≤ 500 sq ft) are exempt.
Permits required
CA state lawBuilding permit
Only a ministerial building permit — no conditional use permit or discretionary design review for a qualifying ADU.
Gilroy-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
Historic Districts
ADUs in historic districts subject to ministerial review for consistency with Secretary of the Interior’s Standards.
Fire Sprinklers
Sprinklers not required for ADUs unless primary dwelling requires them.
Gilroy sets a local detached ADU maximum of 1,000 sq ft (below the state cap), allows above-garage ADUs up to 24 ft, and requires ministerial review for ADUs in historic districts. No owner-occupancy is required for ADUs, but JADUs may require it per state law.
Frequently asked questions
Can I build an ADU in Gilroy?
Yes. California's statewide ADU law requires Gilroy to approve a qualifying accessory dwelling unit ministerial (by right), plus a junior ADU (JADU) on a single-family lot.
How big can an ADU be in Gilroy?
A detached ADU of at least 1,000 sq ft must be allowed, and an ADU of 800 sq ft can never be zoned out by floor-area or lot-coverage limits. A JADU can be up to 500 sq ft.
What are the setback requirements for an ADU in Gilroy?
Side and rear setbacks are limited to 4 ft. ADUs must not encroach on required front yard unless it would preclude an 800 sq ft ADU with 4-ft setbacks.
Is parking required for an ADU in Gilroy?
Up to 1 space. No parking can be required within ½ mile of transit, for conversions, or for units inside the primary home. When a garage is converted, replacement parking is not required.
How long does ADU approval take in Gilroy?
A complete application must be acted on within 60 days, with ministerial (by right) — no public hearing or discretionary design review for a qualifying ADU.
Do I have to live on the property to build an ADU in Gilroy?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Gilroy Zoning Code Article LIV (Accessory Dwelling Units), §§ 30.54.10–30.54.60; last amended Ord. No. 2025-09, § 2 (Exh. A), 11-17-25; current through Ord. 2026-01, 1/5/2026
- § 30.54.30(d)(1)
- § 30.54.30(d)(2)
- § 30.54.30(f)
- § 30.54.30(g); § 30.54.30(g)(1)-(6)
- § 30.54.30(g)(2)
- § 30.54.40; State Gov. Code § 66315
- § 30.54.30(h)(2)
- § 30.54.20(d)
- Cal. Gov. Code §§ 66310–66342 (ADU Law)
- HCD 2025 Accessory Dwelling Unit Handbook
- Cal. Gov. Code § 66317 (ministerial approval, 60-day deadline)
- Cal. Gov. Code § 66323 (by-right ADU/JADU, 800 sq ft, 4-ft setbacks)
- Cal. Gov. Code § 66333 (junior ADUs)
- Cal. Gov. Code § 66321 (size minimums & height)
- Cal. Gov. Code § 66322 (ADU parking; § 66334 covers JADU parking)
- Cal. Gov. Code § 66311.5 (impact fees: none for an ADU ≤ 750 sq ft or JADU ≤ 500 sq ft)
Last updated 2026-06-25. This is an AI-assisted summary of Gilroy's ADU rules, drawn from its published ordinance and California ADU law — general information, not legal advice, and it may be incomplete or out of date. Verify the controlling rule for your specific parcel with Gilroy Planning before relying on it.
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