Frequently Asked Questions about ADUs


What is an Accessory Dwelling Unit (ADU)?

An ADU is an independent dwelling unit 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 kitchen with a permanently installed cooking appliance, and a full bath with facilities for sanitation and bathing. Structures without all these facilities are not considered ADUs.

What is a Junior ADU (JADU)?

A JADU is a dwelling unit contained within the walls of a proposed or existing dwelling unit. 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.

What is an Efficiency Kitchen?

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. Dwelling units may include one efficiency kitchen in addition to a standard 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.


Can I Build an ADU on My Property?

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 (or 454-2130).

How Many ADUs Can I Build on My Property?

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

Properties with single family homes may have one ADU and one JADU per single family dwelling.

The single-family ADU rules also apply to “semi-detached” dwellings, which are two dwellings on separate properties that share a wall at the property line. These types of dwellings are also called “half-plexes.”

Note that according to the building code, single-family homes cannot have more than two attached, independent dwelling units. For this reason, if the existing single-family dwelling is semi-detached, or if there is an existing or planned JADU attached to the single-family dwelling, then an ADU associated with that single-family dwelling must be detached.

Lots with multifamily dwellings (multiple attached primary dwelling units on the same parcel) are allowed have up to two New Construction detached ADUs, plus up to 25% of units can have Conversion ADUs created only 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 a “Level 5 review” (Zoning Administrator public hearing). 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: or calling 454-2130.

Is There Any Limit on the Number of ADUs That Can Be Built in the County, or in My Neighborhood Each Year?

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

Do I Need to Live on the Property?

It depends. On properties with ADUs and JADUs that were permitted before January 1, 2020, the owner (or an immediate family member 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.

Can I Use a ‘Tiny Home’ as an ADU?

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 §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.

What Are The Rules Regarding Conversion of Non-Habitable (Non-Living) Space Such As Garages And Storage Areas?

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.


What Permissions Do I Need in Order to Legalize or Build an ADU?

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 or 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.

There Is an Accessory Structure On My Property That Was Not Contructed With Permits. Can I Convert It Into an ADU? There Is an ADU That Was Built Without Permits On My Property. Can I Legalize It?

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.

How Do I Start the Permit Process?

Review the How-To Guide and other information available on the County’s ADU website: Any additional questions you may have regarding the permit process can be addressed by the Zoning Counter staff at 454-2130 or

The State Law Says That There US a 60-Day Review For ADU Permits. Does That Mean I WIll Receive My Permit 60 Days After I Submit an Application?

Potentially. When you submit an ADU building permit application, the Planning Department staff has 60 days to review that application and issue either a building permit, or a letter stating any further submittals or corrections to plans that are required. Each time you resubmit an application with corrections, the 60-day review clock re-sets. When you submit a complete and correct ADU building permit application, you will receive a building permit within 60 days of that submittal.

Is a Public Hearing or Public Notice Required?

Not normally. In any residential or mixed use zoning district, ADUs that conform to site standards usually require only a building permit, with no public hearing or public notice.

Can I Build the ADU First and a Primary Dwelling Unit Later?

Yes and no! 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, the 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.

Does Santa Cruz County Have Any ADU Construction Plans That Are "Pre-Approved"?

No, but 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.


What Size ADU Can I Build?

Maximum allowed ADU size 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. 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.

How Do You Calculate ADU Square Footage?

Square footage that counts toward the size of the ADU includes gross 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.

I Have Already Met/Exceeded the Allowed Building Square Footage or Lot Coverage On My Property. Can I Build an 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.

Does an 800-Square Foot ADU Count Toward Total Floor Area On My Property?

Yes. Although an ADU may exceed floor area and lot coverage limits by up to 800 square feet, the ADU still counts toward overall building square footage for the property. In other words, the 800-square foot ADU allowance does not function 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 1,500 square feet. In this example, you may construct an 800-square foot ADU, bringing the total building square footage to 2,300 square feet, but no additional square footage would be allowed on this parcel.

If I Build a New Garage To Serve My ADU, Can I Deduct a 225 Square Foot Floor Area Credit?

No. 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.

Will I Need To Replace Parking If I Convert My Garage To an ADU?

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

Are Any Site Standards Flexible? Can I Reduce Required Setbacks or Build a Taller ADU?

Under certain circumstances, a variance, minor variation 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) §13.10.230 and § 13.10.235. To confer with a planner, email, call 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 §13.10.323(E)(6)(g) for more detail.

I Had a Non-Conforming ADU or Other Accessory Structure That Was Destroyed Or Will Be Demolished. Can I Rebuild an ADU Using The Same Footprint And Dimensions?

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.

Can I Have An Interior Door Between My Home And an Attached ADU?

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

Are the Side and Rear Setbacks Different For an ADU Built Over a Garage?

No. 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 and rear setbacks for ADUs are 4 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 section 13.10.323(E)(6)(f) of the County Code.

Are ADUs Subject to Environmental Constraints Such As Riparian Buffers And Wildlife Habitat Protection Areas?

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

My Parcel Was Part of a Subdivision Where Building Envelope Areas Were Defined. Where Can I Build an ADU?

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.


The Building Code Requires Solar Panels for New Homes. Does This Rule Apply to ADUs?

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 (

My Property Is on Septic. Am I Allowed to Build an ADU?

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 (831-454-3234) early in their process regarding the capacity of the existing system and the feasibility of improving it if necessary.

Does My ADU Need a Separate Water Meter or Sewer Connection?

JADUs and Conversion ADUs do not require a new sewer or water connection and no additional capacity charges will be applied. 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.

What Are the Requirements and Associated Fees of My Water Purveyor/Sanitation District/Fire District?

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.

Do I Need to Install Fire Sprinklers in My 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.

How Do Fire-Rated Wall Assembly Rules Apply to ADUs?

Per the California Building Code, walls 0 to 5 feet from the property lines are required to be one hour fire rated assemblies. You are not allowed any openings (windows) less than 3 feet from the property. Between 3 feet and 5 feet, 25 percent of the wall can have wall openings.

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


How Much Will It Cost to Build an ADU?

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.

Will My Property Taxes Increase?

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.

Are There Reduced Fees for ADUs?

Yes. ADUs less than 750 square feet are exempt from impact fees, and ADUs less than or equal to 640 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. Note that JADUs, while small, are subject to the same fees that are charged for residential renovation projects and do not have the same fee waivers as ADUs.


I Would Like to Rent My ADU. What Do I Need to Know to Become a Landlord?

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.

Can I Rent My ADU as a Vacation Rental or Other Short-Term Basis?

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.