Free Tool · Rules verified July 2026 · Every rule cited to an official source
California ADU rules, in plain English.
California state law sets the floor and largely preempts local rules. Here is what applies statewide, plus verified local rules for the cities and counties we serve. Every non-obvious number links to the official source. Jump to your jurisdiction below.
Some of what's below is new or newly permanent, which can work in your favor if you know it: cities must now confirm your application is complete within 15 business days, and the old requirement to live on your own property before building an ADU is gone for good.
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Before You Plan Around These Numbers
- ·Everything on this page is a preliminary estimate for planning, not a survey, site plan, or permit determination.
- ·The buildable-area outline reflects state-minimum side and rear setbacks only; your front setback follows your home’s zoning and is confirmed in your free property analysis.
- ·Rent figures come from federal Fair Market Rent data for your area. They are a planning benchmark, not a rental guarantee.
- ·Return and payment figures are simplified estimates, not financial advice. Your lender and tax professional have the real numbers.
- ·Permit fees and timelines are directional; permitting is the one step no builder fully controls, and your city has the final word.
- ·The real answer is free: our team confirms all of this in your free property analysis.
- ·This wizard changes which notes it surfaces based on your answers, never the underlying numbers - those come straight from the same verified, cited rules shown throughout this page.
Statewide (preempts local)
Maximum size
Detached ADUs are allowed up to 1,200 sq ft under state law. Cities may cap size lower, but never below 850 sq ft (studio or 1 bedroom) or 1,000 sq ft (2+ bedrooms).12
Guaranteed minimum
Every city and county must allow at least an 800 sq ft, 16 ft tall ADU with 4 ft side and rear setbacks, no matter what local standards say.1
Setbacks
4 ft from side and rear property lines for new construction (0 ft for a conversion within an existing structure). Front setback follows the main home's zoning.1
Height
At least 16 ft is allowed everywhere. Within a half mile walking distance of a major transit stop: 18 ft, plus 2 more ft to match the main home's roof pitch. Attached ADUs may reach 25 ft.1
Approval
Ministerial: approved or denied without a public hearing, and the city or county must act on a complete application within 60 days.1
Owner-occupancy
Not required for a standard ADU, and cities cannot impose it. A Junior ADU (JADU) requires owner occupancy only if it shares a bathroom with the main home.12
Parking
At most 1 space per ADU, with broad exemptions: within a half mile walking distance of public transit, when replacing a garage, and for conversions. Most lots qualify for an exemption.1
Junior ADU (JADU)
A Junior ADU is up to 500 sq ft, created within the walls of a single-family home.1
Impact fees
Waived for ADUs under 750 sq ft. At 750 sq ft or larger, fees must be proportional to the size of the primary dwelling.1
How many per lot
A single-family lot may generally add one ADU plus one JADU. Multifamily lots can add up to 8 detached ADUs (never more than the number of existing units) plus conversion units.12
Separate sale
Where a city opts in, an ADU can be mapped as a condominium and sold separately from the main home (AB 1033).1
Reference: CA Gov. Code 66310-66342 (state ADU law) and HCD's ADU guidance; see the numbered sources at the bottom of this page. This is a plain-English summary, not legal advice. We confirm exactly what applies to your address with a free Property Report.
Verified City Rules
Where a city publishes its own standards, we list only what differs from or adds to the statewide baseline above. Everything not listed follows state law.
San Jose
See our San Jose page →San Jose applies state ADU law directly in its zoning code and runs one of the most ADU-friendly permit shops in California: a dedicated ADU Ally, preapproved plan sets, and condo conversion for selling an ADU separately.
Separate sale
San Jose allows ADU condominium conversions, so an existing ADU can be sold separately once a condo map is approved.3
Local fees
School and parkland impact fees do not apply to ADUs under 750 sq ft. At 750 sq ft or larger, school district and parkland fees apply, and building permit fees scale with ADU size.3
- ·The city states it enacts all state ADU legislation in its zoning code, so the statewide standards are the local standards.
- ·A legally built San Jose home can be eligible for up to three ADUs on one property.
- ·Preapproved ADU plan sets and the ADU Ally desk (adu.ally@sanjoseca.gov) can shorten plan review.
Salinas
See our Salinas page →Salinas rescinded its local ADU chapter in February 2026 and now applies state ADU law directly, so the statewide standards on this page are the local rulebook. The city also keeps pre-approved ADU plans and an ADU guide.
- ·Zoning Code Amendment 2025-001 (adopted February 24, 2026) rescinded Salinas Municipal Code section 37-50.250 and applies state ADU law to ADU applications.
- ·Pre-approved ADU plan sets are available through the Community Development Department.
- ·Our factory is in Salinas, so this is the permit counter we know best.
Santa Cruz (city)
See our Santa Cruz page →The City of Santa Cruz has its own detailed ADU chapter (SCMC 24.16 Part 2) that is more generous than state minimums in places: larger allowed sizes on big lots, 3 ft setbacks for lower units, no parking outside the Coastal Zone, and ADU condos for separate sale.
Maximum size
A new detached ADU may be the larger of 10% of net lot area (up to 1,200 sq ft) or 850 sq ft for a studio or 1 bedroom and 1,000 sq ft for 2+ bedrooms.5
Setbacks
Detached new-construction ADUs need only 3 ft interior side and rear setbacks; any portion over 16 ft tall must sit back at least 4 ft.5
Height
A non-exempt detached ADU can reach 22 ft to the roof peak. Statewide-exemption units follow the state's 16 to 20 ft ladder.5
Parking
No parking is required for an ADU outside the Coastal Zone, and parking removed to build one need not be replaced. Inside the Coastal Zone, one off-street space is required near the shore (the city maps exactly where).5
Separate sale
Santa Cruz allows ADUs to be mapped as condominiums and sold separately (adopted 2025).5
Local fees
ADUs under 750 sq ft fall below the school impact fee threshold; larger units pay school fees based on unit size.5
Short-term rentals
Single-family properties with an ADU are not eligible for the city's short-term rental program; the ADU is meant for long-term housing.5
- ·Coastal Zone parcels may need a Coastal Permit (still no public hearing).
- ·The city runs an ADU legalization program (AB 2533) for units built before 2020.
Watsonville
See our Watsonville page →Watsonville's ADU chapter (Municipal Code 14-23) ties detached ADU size to lot size, lets the biggest lots build two ADUs, and keeps the state impact-fee waiver under 750 sq ft.
Maximum size
By lot size: up to 850 sq ft (1 bedroom) on lots under 6,000 sq ft; 1,000 sq ft (2 bedrooms) under 10,000 sq ft; 1,200 sq ft (3 bedrooms) over 10,000 sq ft. Lots over 12,000 sq ft may instead build two ADUs of up to 750 sq ft each.6
Setbacks
4 ft interior side and rear setbacks; 20 ft front; 10 ft exterior side; 5 ft from an alley.6
Height
Attached and detached ADUs may reach 28 ft; conversions of existing accessory structures are capped at 16 ft.6
Owner-occupancy
Not required for a standard ADU. A JADU requires the owner to live in the main home or the JADU, recorded by deed restriction.61
Parking
One space per unit or per bedroom, whichever is less; tandem on the driveway counts. Waived for conversions and for lots within a half mile of a public transit bus stop, in a historic district, or near a car-share vehicle.6
Local fees
No development impact fees for ADUs under 750 sq ft; larger ADUs pay fees proportionate to the primary home by square footage.6
Short-term rentals
Neither the ADU, the JADU, nor the main home may be rented for under 30 consecutive days.6
- ·State law floors still apply on small lots: every lot is entitled to at least an 800 sq ft ADU regardless of the local size table.
Morgan Hill
See our Morgan Hill page →Morgan Hill follows state ADU standards through Municipal Code chapter 18.84 and runs a pre-approved plans gallery that connects homeowners directly with designers.
Junior ADU (JADU)
A JADU is up to 500 sq ft, may use an efficiency kitchen, can share a bathroom with the main house, and the owner must live on the property.7
How many per lot
A single-family property can have a JADU, an internal conversion or attached ADU, and a detached ADU. Multifamily properties can have up to 8 detached ADUs or up to 25% of the unit count.7
- ·Development standards live in Municipal Code chapter 18.84; the statewide baseline applies.
- ·Pre-approved plans gallery: browse pre-reviewed designs, then complete site-specific planning for your lot.
- ·Special zones (historic, hillside, high fire severity, flood) can limit what you can build; ask the city first.
Gilroy
See our Gilroy page →Gilroy's ADU article (City Code 30.54) is stricter than the state default on detached size: 1,000 sq ft is the cap. In exchange, the city pre-approves plan sets and can issue those permits in about 15 working days.
Maximum size
A detached ADU may not exceed 1,000 sq ft in Gilroy. Attached ADUs are capped at 50% of the main home's floor area, but 850 sq ft (1 bedroom) or 1,000 sq ft (2+ bedrooms) is always allowed.8
Setbacks
4 ft from side and rear lot lines for new construction; no additional setback for conversions rebuilt in the same footprint.8
Height
Detached ADUs: one story and 16 ft, or 18 ft within a half mile of a major transit stop (up to 20 ft to match the main home's roof pitch). Above a detached garage: 24 ft.8
Approval
Ministerial approval or denial within 60 days of a complete application, with no hearing.8
Parking
One space, allowed in the front setback, tandem, or on the driveway. Waived for conversions, lots within a half mile walking distance of public transit, historic districts, or with a car-share vehicle within a block.8
Local fees
ADUs are not subject to charges beyond generally applicable building permit fees, plus utility connection and capacity charges as limited by state law.8
Permit timeline
With a pre-approved plan and complete documents, Gilroy can issue permits in about 15 working days. Custom plans follow the standard 60-day ministerial clock. Site conditions and utilities can add time; permitting is the step nobody fully controls.98
Short-term rentals
ADUs may not be rented for periods under 30 days; a deed restriction records this before permit issuance.8
- ·Pre-approved standardized construction plans make Gilroy one of the fastest ADU permits in the region when your documents are complete.
At A Glance
City vs. city, side by side.
| City | Max size | Setbacks | Height | Parking | Approval |
|---|---|---|---|---|---|
| San Jose | 1,200 ft² | 4 ft | 16 ft | 1 space* | 60 days |
| Salinas | 1,200 ft² | 4 ft | 16 ft | 1 space* | 60 days |
| Santa Cruz (city) | 1,200 ft² | 3 ft | 22 ft | See notes | 60 days |
| Watsonville | 1,200 ft² | 4 ft | 28 ft | See notes | 60 days |
| Morgan Hill | 1,200 ft² | 4 ft | 16 ft | 1 space* | 60 days |
| Gilroy | 1,000 ft² | 4 ft | 16 ft | See notes | 60 days |
*California state law exempts most lots from the parking requirement within a half mile of transit, for conversions, and where an ADU replaces a garage. Full detail and citations are in the sections above.
Local Notes by County
Monterey County
See our Monterey page →Monterey County follows state ADU law and sweetens it with three free pre-designed ADU plans (515, 749, and 1,200 sq ft) that can speed plan check. Coastal parcels need a Coastal Administrative Permit.
Setbacks
An existing structure may be converted, and a new ADU may keep a 4 ft side setback (county code 21.64.030). Standards that would preclude an 800 sq ft ADU must yield.10
Height
New ADUs may be up to 16 ft tall by right under the county's ADU regulations.10
Local fees
The county's 1,200 sq ft pre-designed plan requires impact fees at that size; the 515 and 749 sq ft plans fall under the state impact-fee waiver for units below 750 sq ft.101
Short-term rentals
ADUs cannot be used for short-term rentals in Monterey County.10
- ·Three pre-designed plans (one, two, and three bedroom) in two exterior styles are free to use and go through the normal review process.
- ·A Coastal Administrative Permit is required in the Coastal Zone.
- ·Septic lots under about 1.25 acres usually need an upgraded alternative septic system to add an ADU.
- ·We have built across Monterey County and know the local plan-check process.
Santa Cruz County
See our Santa Cruz page →In unincorporated Santa Cruz County, detached ADU size is tied to lot size: 850 sq ft (studio or 1 bedroom) or 1,000 sq ft (2+ bedrooms) on lots under an acre, and up to 1,200 sq ft on an acre or more. At least 800 sq ft is always allowed.
Maximum size
On lots under 1 acre: 850 sq ft (studio or 1 bedroom) or 1,000 sq ft (2+ bedrooms). On lots of 1 acre or more: up to 1,200 sq ft. An ADU of at least 800 sq ft is always allowed.11
Setbacks
Minimum side and rear setbacks are 4 ft; front setbacks follow the zone district unless waived.11
Height
Detached ADUs inside the Urban Services Line: 16 ft (21 ft with Zoning Administrator approval); up to 24 ft at the roof peak above a detached garage; 18 to 20 ft near transit.11
Parking
Not required for conversion ADUs or JADUs. New-construction ADUs need one space unless the lot is within a half mile walking distance of a transit stop, in a historic district, or near a car-share vehicle.11
Junior ADU (JADU)
A JADU is 150 to 500 sq ft, built entirely within the walls of the existing or proposed home.11
Local fees
The county waives building permit fees for conversions, connection fees for JADUs and conversions, planning permits for units of 750 sq ft or less, and impact fees for units under 750 sq ft.11
Permit timeline
ADU building permit applications are reviewed within 60 days of submittal through the county's online ePlan process. Overall project timing still depends on permitting.12
Short-term rentals
Short-term rental of an ADU or JADU is not allowed; rentals must be for terms longer than 30 days.11
- ·Applies to unincorporated areas (Aptos, Soquel, and similar). The cities of Santa Cruz and Watsonville have their own sections above.
- ·Confirm the exact size cap for your lot with a free Property Report.
Santa Clara County
See our Santa Clara page →State ADU law applies; specific size, height, and design standards vary by city. See San Jose, Morgan Hill, and Gilroy above for verified city rules. Most of our work happens in this county.
- ·Each city sets some local standards on top of state minimums.
- ·We confirm your city's exact rules for your address, free.
San Benito County
See our San Benito page →Follows California state ADU law with relatively few local overlays. Detached ADUs up to 1,200 sq ft, 4 ft setbacks.
- ·Verify any local standards for your parcel with a free Property Report.
San Luis Obispo County
We serve SLO County on a case-by-case basis. State ADU law applies; detached ADUs up to 1,200 sq ft.
- ·Reach out and we will confirm whether we can serve your specific address.
Sources
- 1. CA Gov. Code 66310-66342 (state ADU law)
- 2. CA HCD, ADU and JADU guidance
- 3. City of San Jose, ADU FAQs
- 4. City of Salinas, Zoning Code Amendment 2025-001 (adopted Feb 24, 2026)
- 5. City of Santa Cruz, Accessory Dwelling Units
- 6. Watsonville Municipal Code ch. 14-23 (ADUs and JADUs)
- 7. City of Morgan Hill, Accessory Dwelling Units
- 8. Gilroy City Code 30.54 (Accessory Dwelling Units)
- 9. City of Gilroy, Accessory Dwelling Units
- 10. County of Monterey, ADU Plans and Info
- 11. County of Santa Cruz, ADU Basic Requirements
- 12. County of Santa Cruz, Accessory Dwelling Units
Rules drafted from official sources in July 2026 and reviewed for accuracy; ordinances change, so always confirm with your planning department or let us do it for you, free.
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