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Reflections and Insights


ADUs in Santa Cruz County: What are the Current Regulations?

Diagram showing Single Family Dwellings with a Junior Accessory Dwelling Unit and an Accessory Dwelling Unit.
Accessory Dwelling Units (ADUs) are a trending topic in California, particularly due to the state’s recognition of the housing shortage. Consequently, state laws regulating ADUs have been progressively relaxed, accompanied by increased pressure on local municipalities to simplify the building process. This has led to what is known as the ‘State Mandate,’ resulting in frequent revisions of local ordinances. Keeping up with the evolving rules for designing an ADU has become challenging, with new regulations and policies emerging regularly. This article provides an overview of the current regulations in one local jurisdiction, Santa Cruz County, as of the time of writing.


Accessory dwelling units (ADUs) are allowed on any parcel in Santa Cruz County where the zoning district or General Plan allows residential uses, and there is an existing or proposed primary dwelling. ADUs can be attached or detached from the primary dwelling, new construction, or converted from existing space, and can be standard or junior ADUs.

Key Considerations
• 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 that cannot meet current building code may pursue the County’s Safe Structures 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 rentals (rentals less than 30 days) are not allowed on parcels with ADUs. Properties with ADUs are therefore not allowed to participate in the County’s Vacation Rental or Hosted Rental programs.
• Permits Required: most ADUs require only a building permit, using the County’s online ePlan review process. ADU building permit applications are reviewed within 60 days of submittal. 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.

Number of ADUs Allowed
Parcels with single-family dwellings: one ADU and one JADU are allowed per single-family dwelling. Note that if both an ADU and JADU are proposed to be attached to a single-family dwelling, multifamily building code requirements may apply. On parcels with multifamily dwellings, two detached ADUs are allowed which may be attached to each other, and up to 25% of units can have an ADU converted from existing non-livable space such as a garage or storage area. For parcels with non-conforming density, where the number of existing dwelling units exceeds the density allowed on the parcel by the General Plan, one or more of the dwelling units is considered “non-conforming” and the number of ADUs allowed depends on the specific non-conforming situation.

ADU Size
In Santa Cruz County, for a JADU (Junior ADU), the minimum size is 150 sf up to a maximum of 500 sf. For conversion ADUs, the minimum is 150 sf, with no maximum size. For new construction ADUs the minimum is 150 sf, with a maximum up to 1,200sf based on parcel size.

General Parking Regulations
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.

How Senate Bill SB9 affects ADUs
SB9, which went into effect January 1, 2022, establishes a streamlined process to allowing additional residential dwelling units on any eligible single-family parcel, and to split an eligible single-family parcel into two separate parcels. SB9 also provides more flexible property setbacks and parking standards. It allows for up to four dwelling units per eligible single-family zoned parcel, including up to two (2) primary dwellings (PDs) and either two (2) ADUs or one (1) ADU plus one (1) JADU on any eligible site. Or, if the parcel is eligible and the owner elects, SB permits lot splits resulting in development of one or two PDs, one PD + one ADU or JADU on each resulting lot.

Other Senate Bill SB9 Considerations
SB9 also provides more flexible property setbacks and parking standards. The County’s objective zoning standards guide (see Zoning Matrix, below) details the zoning standards from the County Code and General Plan/Local Coastal Program applicable to each project.

Click to see larger image in a new window.


Is My Parcel Eligible to Add an ADU?
To be considered eligible to build an ADU, several requirements must be met. These include whether the parcel allows residential land use either by zoning or General Plan designation, the presence or absence of a primary dwelling unit at the site, and the physical size of the parcel in question. The County has established an online tool at its website. The tool’s link is:

For Further Reading
• County of Santa Cruz Planning Department webpage pertaining to ADUs is at:
• A summary of regulations passed by the legislature to make it easier to build ADUs can be found at the Department of Housing and Community Development. The link is:
• SB9, The California Home Act, is discussed in an article at the State legislature’s website. The article can be found at:


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See also Reflections and Insights: Implementing the Principles of the Not So Big House



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