California ADU rules · Santa Clara County
Can I Build an ADU in San José?
Yes — you can build an ADU in San José. California's statewide ADU law requires every city, including San José, 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
Local rule1 detached or attached ADU + 1 JADU (local base); up to 1 detached ADU + 1 conversion ADU + 1 JADU (3 accessory units) via the state-mandated path
San José's local standard allows one ADU plus one JADU; the full state-mandated combination of a detached ADU, a conversion ADU, and a JADU (three accessory units) is available where all state criteria are met.
Units on a multifamily lot
Local ruleAt least 1 conversion ADU in existing non-livable space (up to 25% of existing units) + up to 2 detached ADUs
San José caps detached ADUs on a multifamily lot at 2 — below the state default of up to 8. Verify against current state law.
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 rule1,200 sq ft
1,000 sq ft on lots ≤9,000 sq ft; 1,200 sq ft on larger lots. The 800 sq ft state ADU is allowed by right regardless of lot size.
Max attached ADU size
Local rule50% of the primary dwelling, up to 1,000 sq ft (≤9,000 sq ft lot) or 1,200 sq ft (larger lot); at least 800 sq ft always allowed
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
Local rule18 ft
18 ft for a 1-story detached ADU; up to 25 ft / 2 stories for a two-story detached or attached ADU. (Local 1-story allowance already exceeds the 16-ft state baseline.)
Setbacks
Side setback
Local rule0 ft
San José allows a 0-ft side/rear setback for a single-story detached ADU (more permissive than the 4-ft state cap); a 4-ft setback applies for the state-mandated path and for any second story.
Rear setback
Local rule0 ft
0-ft rear setback for a single-story detached ADU; 4 ft for the state-mandated path or a second story.
Front setback
CA state lawNo front setback may block the mandatory 800 sq ft / 16-ft / 4-ft-setback ADU; otherwise per base zone
Separation from main house
Local rule6 ft
San José requires at least 6 ft between a detached ADU and the primary dwelling (state law sets none); the 800 sq ft by-right ADU is not subject to this.
Parking
Parking required
Local ruleNone
San José requires no off-street parking for any ADU or JADU, and no replacement parking for garage conversions.
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
CA state lawNot required
When a garage/carport is demolished or converted to build an ADU, replacement parking cannot be required.
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
CA state lawOnly for a JADU
No owner-occupancy requirement for ADUs (the prior sunset was removed). A JADU may require owner-occupancy, principally where it shares sanitation with the main house.
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.
San José-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
Historic Resources Inventory properties
On a property on the Historic Resources Inventory, an attached ADU must be located at the rear and a detached ADU at least 45 ft from the front property line — placement limits that don't apply to a standard ADU.
Very High Fire Hazard Severity Zones (eastern foothills)
No outright ADU ban in the foothill VHFHSZ, but a project must still meet fire-code access, defensible-space, and ignition-resistant construction standards that can constrain a detached ADU.
San José allows ADUs in every residential zone, requires no parking, scales the detached-ADU cap to lot size (1,000 sq ft up to a 9,000 sq ft lot, 1,200 sq ft above), and is unusually permissive on bulk — a single-story detached ADU may sit on the property line (0-ft side/rear) and reach 18 ft, with two-story ADUs allowed up to 25 ft. Distinctive constraints are site-level: a 6-ft separation from the main house, historic-property placement rules (rear/45-ft-from-front), and foothill fire zones.
Frequently asked questions
Can I build an ADU in San José?
Yes. California's statewide ADU law requires San José 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 San José?
A detached ADU of at least 1,200 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 San José?
Side and rear setbacks are limited to 0 ft. No front setback may block the mandatory 800 sq ft / 16-ft / 4-ft-setback ADU; otherwise per base zone.
Is parking required for an ADU in San José?
None. 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 San José?
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 San José?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- San José Mun. Code §§ 20.80.175–20.80.179 (2024 Supp. 1)
- SJMC §§ 20.80.175–20.80.176
- SJMC § 20.80.176
- SJMC § 20.80.175(D)(1)
- SJMC § 20.80.175(D)(2)
- SJMC § 20.80.175(D)(3)
- SJMC § 20.80.175
- SJMC § 20.80 Part 2.75 (historic siting standards)
- 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 § 66333 (junior ADUs)
- Cal. Gov. Code § 66321 (size minimums & height)
- Cal. Gov. Code § 66323 (by-right ADU/JADU, 800 sq ft, 4-ft setbacks)
- Cal. Gov. Code § 66322 (ADU parking; § 66334 covers JADU parking)
- Cal. Gov. Code § 66314 (local ordinance standards)
- Cal. Gov. Code § 66315 (owner-occupancy)
- 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 San José'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 San José Planning before relying on it.
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