ADU rules, city by city

State law sets the floor everywhere. This is what each city adds on top: whether it runs a pre-approved plan program, what incentives exist, and the local rules worth knowing before you plan. Every row links to the city's own page, which is the authority.

Last gone over 2026-09-10. Programmes get suspended, capped and restarted; confirm before planning around any of them. Not sure which city permits your lot? Check your address →

City	Pre-approved plans	Incentives	Local rules worth knowing	Links
Campbell Santa Clara County	Yes Program →AB 1332 gallery on the ADU Accelerator platform, 'free and low-cost plans' from recommended architects; a site-specific permit is still required.	Suspended Express Plan Check Active Sample plan sets Confirm Park and impact fee reduction	Maximum size. Detached 1,200 sq ft; minimum 150 sq ft. Height. City bulletin says 16 ft; an older code mirror shows 14 ft and one storey. State law guarantees 16 ft (18 ft near transit). Confirm. Design. Detached ADUs are not subject to the city's residential design standards. 3 more on the Campbell page →	ADU page → Planning → Checked 2026-09-10
Cupertino Santa Clara County	Yes Program →Six plans from four vendors, 476 to 991 sq ft, detached only, valley-floor parcels without geologic hazards. Standard fees apply.	Active Impact-fee exemption under 750 sq ft Active Legalisation of pre-2020 units	Streamlined units up to 800 sq ft. 4 ft setbacks, 18 ft detached height (+2 ft near transit), second storey allowed, exempt from FAR, coverage and open space. Larger units. 850 sq ft (studio or one bedroom) or 1,000 sq ft (two or more); attached capped at 50% of the main home; FAR, coverage and open space per zoning; second storey only within half a mile of transit. Up to three ADUs. A single-family lot may hold up to three ADUs in any combination. 4 more on the Cupertino page →	ADU page → Planning → Checked 2026-09-10
East Palo Alto San Mateo County	None we know of	—	—	ADU page → Planning → Checked 2026-08-25
Gilroy Santa Clara County	Yes Program →	—	Also publishes a path for legalizing unpermitted ADUs and JADUs.	ADU page → Checked 2026-08-25
Los Altos Santa Clara County	Yes Program →Nine free city permit-ready detached plan sets (three styles, 525 / 854 / 1,190 sq ft) with full structural and MEP drawings, plus private pre-approved plans.	Active $0 ADU permit and plan-check fees Active Free permit-ready plan sets	Maximum size. Detached 850 sq ft (one bedroom) or 1,200 sq ft (two or more), basement included, garage excluded; attached units also capped at 50% of the main home. Height. Code: detached one storey and 16 ft. The city's information guide lists 18 ft; state law allows 18 ft near transit. Confirm with planning. Daylight plane. 8 ft at the property line rising at 6:12; 5 ft separation from the main home and other structures (waived if it would block an 850 sq ft unit). 4 more on the Los Altos page →	ADU page → Planning → Checked 2026-09-10
Los Altos Hills Santa Clara County	Yes Program →	—	Publishes pre-approved plans already cleared by California HCD, plus a cost calculator. Plans still need a siting conversation with planning, but get a streamlined review.	ADU page → Checked 2026-08-25
Los Gatos Santa Clara County	Yes Program →AB 1332 gallery on the ADU Accelerator platform; modifications to pre-approved plans are not allowed.	Active Single combined application Active Traffic impact fee exemption Confirm Fee waiver for deed-restricted affordable units	Maximum size. 1,200 sq ft; JADU 500 sq ft within the residence including an attached garage. Height. Detached 16 ft; 18 ft within half a mile of major transit (+2 ft to match the main roof); attached up to 25 ft. Coverage and parking. Roofed structures capped at 40% lot coverage in R-1, R-D and R-M; no additional parking for any ADU. 4 more on the Los Gatos page →	ADU page → Planning → Checked 2026-09-10
Milpitas Santa Clara County	Yes Program →For new detached units: reduced plan-review fee and turnaround cut by as much as half.	Limited ADU Incentive Program Active Safe ADU Legalization Active Paid expedited plan review	Maximum size. 850 sq ft (studio or one bedroom) or 1,000 sq ft (two bedrooms); 1,200 sq ft in the Hillside District; attached units capped at 50% of the main home. Height. Detached 16 ft; 18 ft near transit; up to 20 ft if the roof pitch matches the main home. Attached up to 25 ft. Setbacks. Front 25 ft; side and rear 4 ft; at least 5 ft from the main home. 4 more on the Milpitas page →	ADU page → Planning → Checked 2026-09-10
Monte Sereno Santa Clara County	Yes Program →	—	The City Council approved a 50% reduction in building permit and plan check fees for a new ADU, including conversions of an existing pool house or garage.	ADU page (PDF) → Planning → Checked 2026-08-25
Morgan Hill Santa Clara County	None we know of	—	—	ADU page → Checked 2026-08-25
Mountain View Santa Clara County	Yes Program →Detached, new-construction plans pre-approved for local building, fire and Reach Code compliance, published on the city's ADU Accelerator gallery.	Active Legalize Existing ADU program	Ordinance status. HCD's May 2025 letter says Ordinance 02.2024 is non-compliant and the city will process applications under state law until a new ordinance is adopted. Electrical. A new sub-meter for an ADU needs a minimum 125-amp panel (City Code 8.51(D)). Pre-approved plans must meet the city's Reach Code. JADU. Deed restriction required and one dwelling on the lot must be owner-occupied. 1 more on the Mountain View page →	ADU page → Planning → Checked 2026-09-10
Palo Alto Santa Clara County	Yes Program →Pre-approved detached designs on the ADU Accelerator gallery; a gallery plan removes the architectural review of the structure, and a site-specific building permit is still required.	Active Larger units under city standards Active Impact-fee exemptions	State track. 800 sq ft, 16 ft (18 ft near transit, plus 2 ft to match the main roof pitch), 4 ft side and rear setbacks. City track. 900 or 1,000 sq ft; up to 25 ft in the RE zone; at least 3 ft from the main home; additional city standards apply. Privacy standards. Entry facing a different property line than the main home's; obscured glazing on egress windows facing neighbours; sill-height and deck-screening rules; downward lighting. 4 more on the Palo Alto page →	ADU page → Planning → Checked 2026-09-10
San José Santa Clara County	Yes Program →City-reviewed plans from 30+ vendors. With a complete site-specific package the permit may issue the same day as the plan-review appointment.	Active Same-day permits for pre-approved plans Active AB 2533 legalization path	Local standards. The city says its zoning code enacts state ADU law and its ADU Universal Checklist reflects it (Municipal Code 20.30.150). No city-specific dimensional standards beyond state law could be verified. Sold separately. First California city to implement AB 1033: an ADU may be converted to a condominium and sold separately from the main home. Separate meter. PG&E now requires a new ADU to have its own meter (JADUs do not). The site plan must show the sewer point of connection. 3 more on the San José page →	ADU page → Planning → Checked 2026-09-10
Santa Clara Santa Clara County	Yes Program →Building Division program (revised April 2026): plan review at 25% of the standard fee and a 10-business-day first review for unchanged pre-approved plans.	Active 75% plan-review fee discount on pre-approved plans Active Paid expedited review	Review path. ADUs submit as a building permit with no planning entitlement, except a new attached second-storey unit on a single-storey home, which needs Architectural Review. Second storey. A second-storey ADU is ministerial only if it matches the height of the main home. Conversions. No setback required for a conversion rebuilt in the same location and dimensions, or for a unit within existing space. 2 more on the Santa Clara page →	ADU page → Planning → Checked 2026-09-10
Saratoga Santa Clara County	Yes Program →Detached plans pre-reviewed for building-code consistency; complete site-specific submittals deemed complete within 30 days. Check parcel eligibility on the city's GIS tool first.	Active All city fees waived for deed-restricted affordable units	Maximum size. 1,200 sq ft attached or detached; JADU 500 sq ft inside the home. Height. Detached 16 ft on single-family lots, 18 ft on multi-family; attached up to 25 ft or the main-dwelling limit. Coverage. An 800 sq ft unit may exceed the lot's maximum floor area and site coverage. 3 more on the Saratoga page →	ADU page → Checked 2026-09-10
Sunnyvale Santa Clara County	Yes Program →Pre-approved plans gallery on the county's ADU Accelerator platform; plans are bought from the designer and get a streamlined review.	Active Building-permit-only path under 800 sq ft Active Five-year deferred enforcement for pre-2020 units	Maximum size. New detached or attached units: 850 sq ft (studio or one bedroom) or 1,000 sq ft (two or more bedrooms). Interior conversions have no maximum. Height. Detached 16 ft, or 18 ft near transit. Attached up to 25 ft or the main home's height, whichever is lower. Parking. None required, except a detached unit of 800 sq ft or more must replace uncovered spaces it removes. 2 more on the Sunnyvale page →	ADU page → Planning → Checked 2026-09-10
Unincorporated Santa Clara County Santa Clara County	Yes Program →County-owned plans free of charge: 800 sq ft two-bed and 1,200 sq ft three-bed, each in two styles. Staff review only the site-specific items (about four weeks first review, two on resubmittal). Not usable in WUI, flood or geologic-hazard zones.	Active Free County pre-approved plan sets Active AB 2533 legalisation program	Authority. Land outside any city's limits is permitted by County Planning & Development with the County's own standards, not the nearest city's. Septic. Environmental Health must clear a unit on septic: a scaled as-built site plan of the tank and leach field, a pumper's report from the last three years, and a water test; the drainfield is sized by bedrooms. Fire and water. County Fire Marshal standards: fire-protection water supply or approved sprinklers, driveway specifications, and a water source within 150 ft of the structure. 2 more on the Unincorporated Santa Clara County page →	ADU page → Planning → Checked 2026-09-10

The floor under every row

None of the cities above can go under these. Full guide, with the statute cited →

An ADU is allowed on your lot

Every lot zoned for residential use may have at least one ADU, and a single-family lot may also add a JADU. A city cannot say no to the category.

800 sq ft by right

A detached or attached unit of up to 800 sq ft, 16 ft tall, with 4 ft side and rear setbacks must be approved regardless of local lot-coverage or floor-area limits.

Four-foot setbacks

A city cannot require more than four feet from side and rear lot lines for an ADU.

A 60-day decision

Once your application is complete the city has 60 days to approve or deny; 30 if you build from a pre-approved plan.

No replacement parking

Convert or demolish a garage to build an ADU and the spaces you lose never have to be replaced.

No impact fees under 750 sq ft

Prohibited entirely below 750 square feet, and proportional above it.

Ministerial review

Reviewed against an objective checklist. No design review board, no hearing, no discretion about whether they like it.

No owner-occupancy rule for an ADU

A city cannot require you to live on the property for a standard ADU. A JADU is different: since 1 January 2026 owner occupancy is required when the JADU shares sanitation with the main house.