Accessory Dwelling Units

Frequently Asked Questions about ADUs


An ADU is an independent dwelling unit with a dedicated exterior entrance that provides complete living facilities for a household, including permanent provisions for living, sleeping, eating, cooking and sanitation. ADUs can be New Construction or Conversion from existing habitable or non-habitable space. In order to meet this definition, ADUs must have a full kitchen, including a built-in permanently installed cooking appliance, and a full bath with facilities for sanitation and bathing. Structures without all these facilities are not considered ADUs.

A JADU is a dwelling unit contained within the walls of a proposed or existing dwelling unit, with a dedicated exterior entrance. JADUs can be converted from either habitable space (such as an existing bedroom) or non-habitable space (such as a garage or storage area). JADUs may not be more than 500 square feet in size, including additions of no more than 150 square feet. JADUs must include all of the following facilities: independent> provisions for living, sleeping, eating, and cooking (area meeting the definition of an efficiency kitchen), and shared or separate sanitation facilities with the main dwelling unit. Residential areas without all these facilities are not considered JADUs.

JADUs are not required to have interior access to the primary dwelling.  Note that JADUs without interior access to the primary dwelling are considered independent units under the building code, with associated requirements for fire separation.

A "kitchen" is any room or portion of a room used or intended or designed to be used for cooking and/or the preparation of food and containing all of the following: a sink having a drain outlet larger than 1.5 inches in diameter, a refrigerator larger than 2.5 cubic feet, a built-in permanent cooking appliance typically including a full-size gas or 220-volt electric range/oven with a range/hood ventilation system, and space for food preparation and storage.

An "efficiency kitchen" is a limited kitchen facility that includes a sink, a refrigerator, small electric kitchen appliances that do not require electrical service greater than 120 volts, an appropriately sized food preparation counter and storage cabinets. Gas or propane cooking appliances are not allowed.

ADUs are required to have kitchens. JADUs are required to have efficiency  kitchens. Primary dwelling may include one efficiency kitchen in addition to one kitchen, as long as the efficiency kitchen area has interior access to the rest of the dwelling. If a dwelling includes a JADU, then an additional efficiency kitchen outside the JADU is not allowed.

Basic Rules for Building an ADU

Use the Eligibility tool on the ADU website to determine your eligibility and the size of ADU you could build on your property. The tool pulls the relevant factors from the County’s GIS database to determine if a parcel meets the requirements of the Santa Cruz County Code (section 13.10.681) to accommodate an ADU. The determination by the eligibility tool can be verified by the County Planning Dept. at Planning.ZoningInfo@santacruzcountyca.gov (or 831-454-2130).

The maximum number of ADUs allowed on a single property is based on whether the primary dwelling is a single-family home, a group of single-family homes, or multifamily (attached) dwelling units.

Properties with single family homes may have one ADU and one JADU per legal, conforming single-family dwelling.

The single-family ADU rules also apply to attached single family dwellings such as townhomes and semi-detached single-family homes that share a wall at the property line.

Note that according to the building code, single-family homes cannot include more than two attached, independent dwelling units. For this reason, if the proposed primary dwelling plus ADUs and JADUs would result in three or more attached, independent dwelling units, multifamily building code regulations may apply. JADUs that are not internally connected to a primary dwelling are considered independent dwelling units.

Lots with multifamily dwellings (multiple attached primary dwelling units on the same parcel) are allowed have up to two New Construction detached ADUs that must be detached from the primary multifamily dwellings but may be attached to each other. Also, at least one and up to 25% of primary multifamily dwelling units can have Conversion ADUs created from areas that are not currently livable space (such as storage rooms or garages).

Some parcels are developed with more primary dwelling units than are allowed for the parcel. On these “legal non-conforming” parcels, the addition of an ADU or JADU may be considered “intensification” of the nonconforming density and may require discretionary approval before a building permit may be issued. If you have this situation on your parcel, ask Planning Department staff for help in determining the number of ADUs allowed and the permit process: Planning.ZoningInfo@santacruzcountyca.gov or calling 831-454-2130.

Under SB 9, there are two main provisions: allowing two primary dwellings on a single-family parcel, and subdividing a single-family parcel into two parcels.

In terms of the first provision, eligible single family zoned properties are now allowed to have two primary dwellings regardless of density, and each of those primary dwellings can have an associated ADU or JADU. In Santa Cruz County, we already allow groups of single-family dwellings on one parcel, subject to density regulations, so feasibly in Santa Cruz County you could have a parcel with two (or more) primary dwellings plus and ADU and JADU for each of those primary dwellings without needing to rely on SB 9 allowances. 

The other provision of SB 9 is that eligible single family zoned properties can be subdivided into two parcels, with two dwellings on each resulting parcel. In the case of these special subdivisions, called “urban lot splits”, the two dwellings allowed on each resulting parcel can be two primary dwellings, or one primary dwelling and one ADU or JADU.

For more information about SB 9, please see the County’s SB 9 website.

No. There is no overall limit on the number of ADUs in the unincorporated County.

It depends. On properties with ADUs and JADUs that were permitted before January 1, 2020, the owner (or a relative of the owner) is required to live on site. On properties with ADUs permitted during the five-year period from January 1, 2020 through January 1, 2025, owner occupancy is required only if there is also a JADU on the property.

The County requires proof of owner occupancy via a Homeowner’s Tax Exemption filed with the County Assessor or some other official documentation. Property owners have an option to apply for a temporary exception to this owner occupancy requirement at the discretion of the Planning Director.

Not if the “tiny home” is mobile. To meet building code requirements for habitability, every ADU must be placed on a permanent foundation and connected to utilities (SCCC section 13.10.682).ADUs may be conventional construction, pre-fabricated, modular or a mobile home installed on a permanent foundation. The ADU may also be created by converting space in an existing structure. See Types of ADUs page for more information.

Under California law, a tiny home mounted to a chassis with wheels is classified as a Recreational Vehicle (RV), eligible only for occasional or seasonal use and cannot be used as a permanent residence.

Santa Cruz County is considering regulations that would allow tiny homes on wheels to be used for permanent habitation. Please see the tiny homes project website to learn more.

Non-habitable space can be converted to an ADU, following the rules regarding Conversion ADUs. Some storage spaces and garages in new homes may be set up with wall construction and limited pre-run electrical and plumbing utilities to allow for easier future conversion to ADUs.

An underfloor storage area or crawlspace with a dirt floor is not considered to be built space. Development of an underfloor area into an ADU would constitute a New Construction ADU project rather than a Conversion ADU. A JADU cannot be created from an underfloor storage area, because the underfloor area is not located within the walls of the primary dwelling.

Planning and Building Permit Process

If you have an existing ADU that was built without permits, or you would like to create a new ADU, you will need to obtain a building permit using the County’s online ePlan review process. Some ADU projects may require discretionary planning approval before a building permit can be obtained, but this is rare. Certain ADUs inside the Coastal Zone require Coastal findings that are included in the building permit review. Some projects may also require additional permits related to grading or any septic system modifications that might be necessary. Your ADU cannot exceed site structural standards without discretionary review – consult with the Zoning Counter at Planning.ZoningInfo@santacruzcountyca.gov or 831-454-2130.

If you have an existing ADU on your property that was constructed with permits before the County had an ADU ordinance in place, then you do not need to obtain a permit to officially designate that existing space as an ADU.

If there is a structure on your property that was built without permits and it is not possible to bring that structure up to current building code standards without demolishing and rebuilding the structure, you may be eligible for the County’s Safe Structures Program. Under this program, a building inspector performs a health and safety inspection and, pending any required health and safety upgrades, a certificate is granted allowing the structure to be used as housing. ADUs are allowed in structures that have completed the Safe Structures program.

If an ADU can be brought up to current building code but the structure does not meet ADU zoning standards such as height or setbacks, building permits can be obtained for the structure as a “legal nonconforming” ADU.

Per state law and County code, property owners that receive a code enforcement notice regarding an illegally built ADU may request to wait to resolve the code enforcement issue for up to five years, as long as a building inspector does not identify a health and safety issue that requires more urgent attention.

Maybe. A recorded declaration of restriction limiting an existing accessory structure to nonhabitable use must be rescinded to allow ADUs or JADUs in these structures. Geotechnical or other environmental review may be necessary in order to determine whether the declaration may be rescinded.

Review the How-To Guide and other information available on the County’s ADU website: sccoplanning.com/ADU. Any additional questions you may have regarding the permit process can be addressed by the Zoning Counter staff at 831-454-2130 or Planning.ZoningInfo@santacruzcountyca.gov

Not normally. ADUs that conform to site standards usually require only a building permit, with no public hearing or public notice. In the coastal zone, public notice may be required for ADUs requiring a coastal development permit or ADUs in certain non-residential zone districts.

Yes, but only in the case of rebuilding after a disaster, and the location for the development envelope for the future primary dwelling must be indicated on the plans submitted for the ADU. In other cases, when only one dwelling is constructed on a parcel, it is considered a primary dwelling, and standard permit process, development standards and fees apply. However, this initial dwelling can later be “converted” to an ADU, if it meets maximum size and other criteria, and a new primary dwelling can be constructed.

No, but the County is in the process of developing pre-approved plans for single-story detached ADUs, and several pre-approved plan options are expected to be available by mid-2023. Also, check out the ADU online resources page for websites with ADU plans available for use; Although they are not pre-approved for building permits, starting with a pre-drawn plan can save you time and money in the design phase for your ADU project.

Development Standards

Maximum allowed size for New Construction ADUs varies from 800 to 1200 square feet, depending on parcel size, type of ADU, number of bedrooms in the ADU, and the floor area and lot coverage of the existing structures on the parcel. There is no maximum size for Conversion ADUs. Please see the ADU overview page for details. You can also use the Eligibility Tool to find out what ADU size is allowed on a specific parcel.

Square footage that counts toward the size of the ADU includes habitable square footage measured from exterior walls. Garages do not count toward ADU size, even if the ADU is built above or concurrently with a garage, and even if the garage is intended to serve residents of the ADU.

Yes. You may construct an ADU up to 800 square feet, with a height of 16 feet and side and rear setbacks of 4 feet, even if you have already met or exceeded the floor area or lot coverage percentage allowed for your parcel’s zone district.

No. The 800-square foot ADU allowance functions as a “credit” that can be deducted from overall floor area. For instance, let’s say your maximum allowed building floor area on a parcel is 2000 square feet, and you have an existing primary dwelling that is 1,200 square feet. In this example, if you construct an 800-square foot ADU, this square footage would not count toward the maximum allowed square footage, and therefore an additional 800 square feet of building area would still be allowed on this parcel.

When calculating overall building square footage on a residential parcel, one credit of 225 square feet can be deducted for garage floor area for the parcel. If an ADU and primary dwelling both have garages, the garage associated with the ADU is not eligible for an additional floor area credit.

It depends. Outside certain areas in the Coastal Zone, garage conversions do not require replacement parking. Inside these areas, replacement parking is required. See ADU Overview page for more information about parking requirements.

Under certain circumstances, a variance, minor exception or other development permit can provide some flexibility to residential standards:

  • An ADU of up to 800 square feet usually requires only a building permit even if it would exceed the maximum lot coverage floor area ratio (FAR).
  • If you need relief from other site / structural standards, your site may be eligible for a variance or minor exception. Consult Santa Cruz County Code (SCCC) sections 13.10.230 and 13.10.235. To confer with a planner, email Planning.ZoningInfo@santacruzcountyca.gov, call 831-454-2130 or visit the Zoning Counter (closed Fridays).
  • A discretionary permit with design review can provide for extra height of up to 5 additional feet. The review involves a site visit by staff to ensure that an over-height building will not adversely affect neighborhood or scenic values. The permit is decided by the Zoning Administrator at a public hearing. See SCCC section 13.10.681(D)(7)(b)(ii)(D) for more detail.

Yes. As long as there are not safety hazards or environmental constraints per Title 16 of the Santa Cruz County Code, you may demolish and rebuild an ADU in the place of an existing accessory structure, even if that structure does not meet the setback or height limits usually required for New Construction ADUs. Similarly, you may re-build an ADU in the place of a non-conforming ADU or other structure destroyed by a disaster such as a fire. In both cases, the new ADU cannot increase the degree of nonconformity beyond the old structure. For instance, if the old structure was built three feet from the property line, the new ADU cannot be built any closer than three feet from the property line.

The building code allows a connecting door between an ADU and a primary dwelling as long as it meets fire and sound attenuation requirements. Contact the Building Counter for specific information (email planning.buildinginfo@santacruzcountyca.gov).

If a new structure is proposed that includes a garage with an ADU above the garage, the garage portion of the structure is required to meet setback requirements for garages, and the ADU is required to meet setback requirements for ADUs. This could result in some cases with second story ADU walls either projecting out or stepped back from first story garages. 

Side setbacks for ADUs are 4 feet and rear setbacks are 8 feet for ADUs taller than 16 feet. Side and rear setbacks for garages are in some cases larger, and in other cases smaller than those for ADUs. The side and rear setback for garages in rural areas is generally 20 feet, whereas the setback in urban areas is generally 10 to 15 feet. However, on urban lots less then 10,000 square feet, the County Code allows for a 50% to 100% reduction of side and rear yard garage setbacks, with certain conditions and approvals. See details in SCCC section 13.10.323(E)(6)(f).

Yes. All development limitations related to environmental constraints as described in Title 16 of the Santa Cruz County Code apply to ADU projects.

It depends. On sites with defined building envelopes, it is recommended that you plan for an ADU that is attached or close to the primary dwelling, within the defined building envelope area of the site. Approval of an ADU location outside the defined building envelope may require discretionary approval to modify the subdivision agreement. Also, the regulations of Title 16 of the Santa Cruz County Code may necessitate environmental review for building locations in hazard or environmentally sensitive areas outside approved building envelopes.

Note that if your home is part of a Home Owner Association (HOA) with regulations related to ADUs, such regulations are allowed by state law, as long as these regulations do not prohibit ADUs. For instance, an HOA could allow Conversion ADUs but not New Construction ADUs.

Utility Requirements

Yes. As of January 1, 2020, all detached New Construction ADUs are subject to the same solar PV requirements as new homes. For more information, click here or email the Building Counter (planning.buildinginfo@santacruzcountyca.gov).

Yes, if your septic system can handle the additional flow from the ADU or can be upgraded to do so. Anytime you add bedrooms or convert existing bedrooms to ADUs or JADUs, the septic requirements increase. Applicants should consult with Environmental Health Services (831-454-2022) early in their process regarding the capacity of the existing system and the feasibility of improving it if necessary.

JADUs and Conversion ADUs do not require a new sewer or water connection and no additional capacity charges can be applied, except if they are built concurrently with primary dwellings. New Construction ADUs may require a separate sewer or water connection. A local agency, special district, or water corporation will determine whether a separate utility connection is required, and the connection fee or capacity charge will be proportionate to the burden of the ADU on the water or sewer system.

Special districts have varying requirements and fees that make construction more expensive in certain neighborhoods. The ADU Fee, Cost and Cash Flow Estimator Tool calculates utility fees charged by Santa Cruz County, but does not calculate fees for all special districts. The ADU Eligibility Tool will identify the special districts that serve your property and provide links to their websites. Contact your district directly to find out the requirements and costs of building or legalizing an ADU.

Fire sprinklers are generally required in an ADU only if they are present or being installed in the primary home on the parcel. However, you will still need approval from the appropriate fire district and will need to comply with the fire code. Per fire code, sprinklers are required for projects involving an addition totaling more than 50% of the primary dwelling square footage. This means that sprinklers may be required if your project involves an attached ADU exceeding 50% of the primary dwelling square footage on its own or when combined with other concurrent additions to the primary dwelling. Also, a fire district may require extra on-site water storage for an ADU that is not sprinklered. In this circumstance, installing sprinklers in the ADU may be the most cost-effective option for meeting fire code requirements.

Per the California Building Code, walls of structures that are not protected with a fire-sprinkler system shall be one hour fire rated assemblies when located less than 5 feet from the property line. No openings (windows or doors) are allowed less than 3 feet from the property line, and shall be maximum 25% of the wall area when located between 3 and less than 5 feet from the property line. For fire-sprinklered structures, walls less than 3 feet from the property line shall be one hour fire rated assemblies and openings are not allowed less than 3 feet from the property line. 

For ADUs and independent JADUs that are attached to primary dwellings, fire-rated separation is required between units.

Estimated Cost

Your costs will vary with the type of unit – are you converting part of your existing home or building a new cottage in the back yard? Are you building a JADU or standard ADU? Are you building a garage at the same time? Are you utilizing a mobile home, modular unit or kit-construction? There are County fees involved, as well as hard (material) and soft (labor) construction costs. In some cases, higher upfront ADU costs may be worth it if you can achieve a higher rental income from the ADU. You can use the ADU Fee, Cost and Cash Flow Estimator Tool and review the Cost Considerations page to learn more about estimated costs and financing options for your ADU.

Constructing and ADU will incrementally increase the value of your property, and the tax on that amount of increase is added to the tax that was assessed before the improvement. However, the base value of the property is not reassessed, and any tax advantages that exist, for example, from longtime ownership with no reassessment, will not be affected. Property Tax implications are discussed in greater detail in Section 7 of the ADU Financing Guide.

Yes. ADUs less than 750 square feet are exempt from both impact fees and most building permit review fees. These savings can add up. For example, the County fees for a 750 square-foot new construction ADU are about $25,000, compared to about $5,000 for a 640-square-foot new construction ADU. 

Renting an ADU

Section 8 of the ADU Financing Guide contains a list of resources for a successful renting experience including guidance about creating a lease, tips on selecting tenants, information to help you understand your legal responsibilities and guidance on maintaining a rental unit. Helpful links are also available in the Landlord section of our Resources page.

No. An ADU cannot be used as any type of short-term rental, and an ADU cannot be located on a property with an active Vacation Rental or Hosted Rental permit. Any existing Vacation Rental or Hosted Rental permit must be forfeited before a permit can be issued to construct an ADU.