Santa Cruz County is one of the friendlier places on the Central Coast to build an accessory dwelling unit, but it is also in the middle of rewriting its rules. The County adopted updated ADU regulations in June 2026, and they take effect only once the California Coastal Commission certifies them. In the meantime, state ADU law sets the floor, and where the older County code conflicts with it, state law wins.
RDD Solutions is a residential design and drafting firm based in Carmel. We prepare permit-ready ADU plans for homeowners and contractors in Monterey and Santa Cruz Counties. We don’t build. This guide covers what you can build in unincorporated Santa Cruz County, how the permit process runs, and what your plans need to show.
Santa Cruz County ADU Rules: The Short Answer
On most residential lots in unincorporated Santa Cruz County you can build a detached ADU, an attached ADU, a converted ADU inside existing space, and a junior ADU (JADU). The County must approve or deny a complete application within 60 days, with no public hearing. An ADU of at least 800 square feet with 4-foot side and rear setbacks can’t be blocked by local size, lot coverage or floor-area limits. ADUs under 750 square feet pay no impact fees.
Which Rules Apply: County, City or State?
Start with where the property is. Santa Cruz County’s ADU code covers only the unincorporated county, including Aptos, Soquel, Live Oak, Pleasure Point, Ben Lomond, Boulder Creek, Felton, Corralitos and La Selva Beach. The four incorporated cities each have their own ADU ordinance:
- City of Santa Cruz
- Capitola
- Scotts Valley
- Watsonville
All of them sit on top of the same state law, Government Code §§ 66310–66342. That is why the core protections below apply everywhere in the county, even where local details differ.
The 2026 Update: Where Santa Cruz County’s ADU Ordinance Stands
In February 2025, the state Department of Housing and Community Development (HCD) reviewed the County’s 2021 ADU ordinance and found nine places where it didn’t comply with state law. They included an 8-foot rear setback for taller ADUs (state law caps side and rear setbacks at 4 feet), an owner-occupancy requirement and recorded deed restriction for ADUs (both now prohibited), and fire sprinkler provisions that went beyond what state law allows.
The County adopted a revised ordinance in 2025, but Coastal Commission staff could not recommend certifying it because of conflicts with agricultural land policies. The County revised it again, and the Board of Supervisors adopted the update on June 9, 2026. It takes effect after Coastal Commission certification.
What that means for you: state law already applies today. Where the County’s older code is stricter than state law allows, the state rule governs. If you are designing now, design to the state rules and the County’s proposed standards, and confirm with Planning which version your permit will be reviewed under.
What You Can Build: Santa Cruz County ADU Sizes and Height Limits
These are the standards in the County’s updated ordinance, which track state law closely.
| ADU type | Maximum size |
|---|---|
| Junior ADU (JADU) | 500 sq ft, inside the existing or proposed home |
| Conversion ADU | No maximum, within existing space |
| Attached ADU | 850 sq ft (studio or one bedroom) or 1,000 sq ft (two or more bedrooms), or 50% of the main home, whichever is larger |
| Detached ADU, lot under one acre | 850 sq ft (studio or one bedroom) or 1,000 sq ft (two or more bedrooms) |
| Detached ADU, lot one acre or more | 1,200 sq ft |
An ADU of at least 800 square feet is always allowed, as long as it meets the 4-foot side and rear setbacks and the height limit. Under the update, up to 800 square feet of ADU area is excluded from lot coverage and floor area ratio.
Height: inside the Urban Services Line, a new detached ADU is limited to 16 feet. That rises to 18 feet (plus 2 feet to match the main home’s roof pitch) within half a mile of qualifying transit, and to 18 feet on lots with a multistory multifamily building. An ADU above a detached garage can reach 20 feet at the wall and 24 feet at the peak. An attached ADU can generally reach 25 feet or the zone’s height limit, whichever is lower, under state law.
Setbacks, Parking and Fees
Setbacks
For new construction, side and rear setbacks are 4 feet or the zone’s setback, whichever is less. The zone’s front setback applies, but it can’t be used to block an ADU of 800 square feet or less. A conversion of existing space can keep the existing setbacks. Separation between buildings is set by the Building and Fire Codes rather than a fixed distance.
Parking
No parking is required for a JADU, a conversion ADU, or a detached ADU of 800 square feet or less that meets the setback and height rules. Other new ADUs need one space, which can be tandem or in a setback. State law also waives parking within half a mile of public transit, in a historic district, or within a block of a car-share space. A few listed coastal neighborhoods keep stricter parking rules, so check if you’re near the shoreline.
Fees
ADUs and JADUs under 750 square feet pay no impact fees. From 750 square feet up, impact fees are charged in proportion to the size of the main home. Utility connection fees and capacity charges are separate and can still apply, especially for a detached ADU with its own connections.
The Santa Cruz County ADU Permit Process, Step by Step
1. Check the parcel
Confirm the zoning, whether the parcel is inside the Urban Services Line, whether it’s in the Coastal Zone, and whether it’s on sewer or septic. The County offers an online eligibility tool and free technical assistance for qualifying homeowners. Parcels outside the Urban Services Line are often on septic, and the septic system’s capacity can decide where an ADU goes and how many bedrooms it can have.
2. Measure what’s there
Most homes don’t have usable drawings of their existing conditions. A conversion or attached ADU needs as-built drawings of the existing house; a detached ADU needs an accurate site plan showing setbacks, utilities and slopes.
3. Choose custom or pre-designed plans
The County maintains a pre-designed ADU plans program that can shorten design. Pre-designed plans still need a site plan, utility connections and any site-specific engineering. A custom design makes sense on sloped, irregular or constrained lots, or when the ADU needs to match the main house.
4. Prepare the permit set
A complete set typically includes a site plan, floor plans, elevations, sections, structural drawings and calculations, Title 24 energy compliance, and plumbing, mechanical and electrical information. See what goes into a set of ADU plans.
5. Submit and track the 60-day clock
Under state law, the County must act on a complete ADU application within 60 days. If it doesn’t, the application is deemed approved. In the Coastal Zone, a coastal development permit may also be needed, and state law now puts those reviews on the same 60-day schedule. Expect plan-check comments; a complete, well-coordinated set is what keeps correction rounds short.
6. Respond to corrections and issue
Once corrections are resolved, the building permit is issued and a licensed contractor can start.
Already Have an Unpermitted ADU in Santa Cruz County?
State law (AB 2533) lets owners legalize ADUs and JADUs built before January 1, 2020, with limits on the fees and upgrades a local agency can require unless there is a health and safety hazard. The County’s update carries this forward until January 1, 2030. Legalizing starts with documenting the unit as it stands. See what happens if you build without a permit in California.
Requirements above were checked against Santa Cruz County planning documents and HCD materials in October 2026. The County’s updated ordinance awaits Coastal Commission certification, so confirm current rules with County Planning (701 Ocean St., 4th Floor, Santa Cruz; 831-454-2580) before you design.
Related ADU Guides
- California ADU law in 2026
- How to build an ADU in Monterey County
- What qualifies as an ADU in California
- ADU size guide: what fits in 500 to 1,200 sq ft
- Does an ADU increase property taxes?
Santa Cruz County ADU FAQs
How big can an ADU be in Santa Cruz County?
Under the County’s updated rules, a detached ADU can be 850 square feet (studio or one bedroom) or 1,000 square feet (two or more bedrooms), or 1,200 square feet on a lot of one acre or more. A JADU is limited to 500 square feet, and a conversion of existing space has no maximum. An ADU of at least 800 square feet is always allowed.
How long does an ADU permit take in Santa Cruz County?
State law requires the County to approve or deny a complete ADU application within 60 days. The total time also depends on design, how complete the submittal is, and how many correction rounds plan check needs.
Do I have to live on the property to build an ADU in Santa Cruz County?
No. State law prohibits owner-occupancy requirements for ADUs. A JADU still requires the owner to live in either the JADU or the main home.
Are there impact fees for ADUs in Santa Cruz County?
Not for ADUs or JADUs under 750 square feet. Larger ADUs pay impact fees proportional to the size of the main home. Utility connection fees can still apply.
Do Santa Cruz County rules apply in the City of Santa Cruz or Capitola?
No. The County’s ADU ordinance covers unincorporated areas only. The City of Santa Cruz, Capitola, Scotts Valley and Watsonville each have their own ADU rules, all built on the same state law.
Can I build an ADU on a property with septic in Santa Cruz County?
Often, yes, but the septic system has to support it. Capacity, the leach field and its replacement area can limit where the ADU goes and how many bedrooms it can have, so check the septic early.
Get Your Santa Cruz County ADU Plans Drawn
Tell us the address and what you want to build. We’ll check the parcel, tell you which rules and review track apply, and prepare a permit-ready plan set. Contact RDD Solutions.