Since 2016, state ADU laws have continued to evolve. Recent changes to state ADU law intend to address barriers, streamline approval, and expand potential capacity for ADUs, recognizing their unique importance in addressing California’s housing needs. The County’s local ADU regulations were last updated for consistency with state ADU laws in 2022. While the County is in the process of updating its ADU regulations, the information on this website has been updated for consistency with more recent updates to state ADU law. More information on recent changes to State ADU law may be obtained by referring to the latest edition of the HCD ADU Handbook January 2025 (with January 2026 Addendum).

Structure Legality. Only structures constructed legally may be converted to ADUs. Illegal structures may also be converted to ADUs but will be treated as new construction projects with associated requirements. Property owners seeking to legalize ADUs in illegal structures may be eligible for the SB 13 program or the AB 2533 program.

Septic Requirements. Parcels on septic may require septic system upgrades and should contact the Environmental Health Department for more information.

Short-Term Rentals. Short-term rental of an ADU or JADU is not allowed. Rental of an ADU or JADU must be for a term longer than 30 days.

Most ADUs require only a building permit, using the County’s online ePlan review process. State ADU law mandates specific timelines for ADU building permit applications. The timelines may be extended if the ADU is part of an application for a new single-family dwelling.

Additional review may be required before a building permit may be issued for certain changes to non-conforming dwellings, or for ADUs located in the coastal zone.

Areas zoned to allow single-family dwelling residential use: One ADU converted from an existing structure, one JADU, and one detached new construction ADU are allowed per lot.

Areas zoned to allow multifamily dwelling residential use: On a lot with an existing multifamily dwelling, no more than eight detached ADUs, not to exceed the number of existing units on the lot. In addition, multiple ADUs may be created within the existing multifamily dwelling structure from areas not used as livable space, with the number of conversion ADUs not exceeding 25 percent of the existing multifamily dwelling units. On a lot with a proposed multifamily dwelling, not more than two detached ADUs.

JADU: Minimum 150 sf, maximum 500 sf

Conversion ADUs: Minimum 150 sf, no maximum size

New Construction ADU Attached: 850 square feet (studio or one bedroom), 1,000 square feet (two or more bedrooms), or, if there is an existing primary dwelling, 50 percent of existing primary dwelling habitable square footage, whichever is larger.

New Construction ADU, Detached: On a parcel less than one acre, 850 square feet (studio or one bedroom), or 1,000 square feet (two or more bedrooms). On a parcel greater than or equal to one acre, 1,200 square feet.

Note that State law requires that an ADU of at least 800 square feet shall be allowed.

Parking is not required for Conversion ADUs or JADUs. Property owners converting garages to ADUs do not need to replace lost parking spaces except in certain coastal areas.

New Construction ADUs require one new parking space, except in the following locations when outside certain coastal areas:

• Historic districts
• Within one block of designated car share parking
• Within ½ mile walking distance of any transit stop (except in designated coastal areas )

Coastal Parking Regulations:

• Within the Live Oak Designated Area (LODA), Seacliff/Aptos/La Selva Designated Area (SALSDA), Davenport/Swanton Designated Area (DASDA), and Opal Cliff Drive between 41st Ave and the City of Capitola, one parking space is required for new construction ADUs, with no exceptions, and replacement parking is required when existing parking is demolished or converted for construction of an ADU.

New Construction ADUs have special setbacks and height standards that define the building envelope for these structures.

• Minimum Setbacks from Property Line
  • Minimum front setbacks: standard for the zone district. A front setback shall not be imposed if it would preclude construction of an ADU no more than 800 square feet and adheres to 4-foot minimum rear and side setbacks and other setback requirements.
  • Minimum side and rear setbacks: 4 feet
  • Minimum separation between ADU and other structures: As required by building and fire codes. Learn more here.
• Maximum Height
  • Attached ADUs: standard for the zone district (usually 28 feet)
  • Detached ADUs outside the Urban Services Line: standard for the zone district (usually 28 feet)
  • Detached ADUs inside the Urban Services Line: 16 feet (21 feet allowed with Zoning Administrator approval)
  • ADUs above Detached Garages inside the Urban Services Line: 24 feet at roof peak, 20 feet at top of exterior wall
  • Detached ADU that is within one-half of one mile walking distance of a major transit stop or a high-quality transit corridor: 18 feet (20 feet if roof pitch aligns with the roof pitch of the primary dwelling unit)
• Maximum Floor Area Ratio and Lot Coverage. ADUs are subject to standard FAR and lot coverage, except that an ADU up to 800 sf is allowed, regardless of FAR and lot coverage.

• Coastal Special Communities
  • Pleasure Point: Maximum height for ADUs above Detached Garages: Maximum 22 feet at roof peak, 18 feet at top of exterior wall, and meet standards of the PP combining zone district
  • Seascape Beach Estates: ADUs follow setbacks, height, FAR and lot coverage standards for the SBE combining zone district

Permitting, planning and other fees vary with ADU type and parcel location. To the extent fees are based on size of the unit, number of bedrooms or project valuation, ADU design can influence fee costs. See the ADU Fee, Cost and Cash Flow Estimator for more information. Certain fees are waived or reduced for ADUs as follows:

• Reduced building permit fees for Conversion ADUs.
• Waiver of sewer and water connection fees for JADUs and Conversion ADUs.
• Waiver of Planning Department permit fees for ADUs ≤ 750 sf.
• Waiver of impact fees for ADUs less than 750 sf. Impact fees for larger ADUs are proportional to square footage.
• Waiver of transportation and roads fees when no parking is required for ADU.
• Waiver of Affordable Housing Impact fee for ADUs of less than 750 sf (includes JADUs).

Dwelling units may include up to one "efficiency kitchen” in addition to one standard kitchen. Adding an efficiency kitchen to an existing bedroom, den, or family room can create a separate living space for a family member or a renter, if interior access to the rest of the house is maintained. In some cases, an efficiency kitchen may be an appropriate alternative to a JADU. See the Types of ADUs page to learn more about the “Efficiency Kitchen Alternative.”