Hillsborough Municipal Code Ch. 17.52 Accessory Dwelling Units and Junior Accessory Dwelling Units

Footnotes:

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Editor's note— Ord. No. 800, § 4(Exh. A), adopted April 13, 2026, repealed Ch. 17.52 and enacted a new Ch. 17.52 as set out herein and as may later be amended. Former Ch. 17.52 pertained to similar subject matter and derived from Ord. No. 763, adopted January 13, 2020; Ord. No. 768, adopted March 8, 2021; Ord. No. 775, adopted November 22, 2021; Ord. No. 777, adopted December 13, 2021; Ord. No. 778, adopted December 13, 2021; Ord. No. 787, adopted December 12, 2022; and Ord. No. 796, adopted December 9, 2024.

As used in this chapter, terms are defined as follows:

"Accessory dwelling unit" or "ADU" means an attached or a detached residential dwelling unit that provides complete independent living facilities for one or more persons and is located on a lot with a proposed or existing primary residence. All references in this code to "second unit" refer to an ADU. An accessory dwelling unit also includes the following:

1. An efficiency unit, as defined by Section 17958.1 of the California Health and Safety Code; and

2. A manufactured home, as defined by Section 18007 of the California Health and Safety Code.

"Accessory structure" means a structure that is accessory and incidental to a dwelling located on the same lot.

"Complete independent living facilities" means permanent provisions for living, sleeping, eating, cooking, and sanitation on the same parcel as the single-family or multifamily dwelling is or will be situated.

"Efficiency kitchen" means a kitchen that includes all of the following:

1. A cooking facility with appliances.

2. A food preparation counter and storage cabinets that are of a reasonable size in relation to the size of the JADU.

"Junior accessory dwelling unit" or "JADU" means a residential unit that satisfies all of the following:

1. It is no more than five hundred square feet of interior livable space in size.

2. It is contained entirely within an existing or proposed single-family structure. An enclosed use within the residence, such as an attached garage, is considered to be a part of and contained within the single-family structure.

3. It includes its own separate sanitation facilities or shares sanitation facilities with the existing or proposed single-family structure.

4. If the unit does not include its own separate bathroom, then it contains an interior entrance to the main living area of the existing or proposed single-family structure in addition to an exterior entrance that is separate from the main entrance to the primary dwelling.

5. It includes an efficiency kitchen, as defined above.

"Livable space" means a space in a dwelling intended for human habitation, including living, sleeping, eating, cooking, or sanitation.

"Living area" means the interior habitable area of a dwelling unit, including basements and attics, but does not include a garage or any accessory structure.

"Nonconforming zoning condition" means a physical improvement on a property that does not conform with current zoning standards.

"Passageway" means a pathway that is unobstructed clear to the sky and extends from a street to one entrance of the ADU or JADU.

"Proposed dwelling" means a dwelling that is the subject of a permit application and that meets the requirements for permitting.

"Public transit" means a location, including, but not limited to, a bus stop or train station, where the public may access buses, trains, subways, and other forms of transportation that charge set fares, run on fixed routes, and are available to the public.

"Tandem parking" means that two or more automobiles are parked on a driveway or in any other location on a lot, lined up behind one another.

(Ord. No. 800, § 4(Exh. A), 4-13-2026)

A. Purpose. The purpose of this section is to allow and regulate ADUs and JADUs in compliance with Chapter 13 of Division 1 of Title 7 of the California Government Code.

B. Effect of Conforming. An ADU or JADU that conforms to the standards in this section will not be:

1. Deemed to be inconsistent with the town's general plan and zoning designation for the lot on which the ADU or JADU is located.

2. Deemed to exceed the allowable density for the lot on which the ADU or JADU is located.

3. Considered in the application of any local ordinance, policy, or program to limit residential growth.

4. Required to correct a nonconforming zoning condition. This does not prevent the town from enforcing compliance with applicable building standards in accordance with Health and Safety Code Section 17980.12.

C. Approvals. The following approvals apply to ADUs and JADUs created under this section:

1. Ministerial ADU and Building Permits Required. Every ADU and JADU requires an ADU permit and a building permit. The city will review and approve permit applications in accordance with subsection C.3. below.

2. Processing Fee. The city may charge a fee to reimburse it for costs incurred in processing ADU permits, including the costs of adopting or amending the town's ADU ordinance. The ADU-permit processing fee is determined by the director of community development and approved by the city council by resolution.

3. Process and Timing.

a. Completeness.

(1) Determination in Fifteen Days. The town will determine whether an application to create or serve an ADU or JADU is complete and will provide written notice of the determination to the applicant within fifteen business days after the town receives the application submittal.

(2) Incomplete Items. If the town's determination under subsection (1) above is that the application is incomplete, the town's notice must list the incomplete items and describe how the application can be made complete.

(3) Cure. After receiving a notice that the application is incomplete, the applicant may cure and address the items that were deemed by the town to be incomplete.

(4) Subsequent Submittals. If the applicant submits additional information to address incomplete items, within fifteen business days of the subsequent submittal the town will determine in writing whether the additional information remedies all the incomplete items that the town identified in its original notice. The town may not require the application to include an item that was not included in the original notice.

(5) Deemed Complete. If the town does not make a timely determination as required by this subsection a, the application or resubmitted application is deemed complete for the purposes of subsection c. below.

(6) Appeal of Incompleteness. An applicant may appeal the town's determination that the application is incomplete by submitting a written appeal to the city clerk. The city council will review the written appeal and affirm or reverse the completeness determination and provide a final written determination to the applicant within sixty business days after receipt of the appeal.

b. No Discretion or Hearing. Ministerial permits for an ADU or JADU are considered and approved without discretionary review or a hearing.

c. Deadline to Approve or Deny Ministerial Approvals. The town must approve or deny an application to create an ADU or JADU within sixty days from the date that the town receives a complete application. If the town has not approved or denied the complete application within sixty days, the application is deemed approved unless either:

(1) The applicant requests a delay, in which case the sixty-day time period is tolled for the period of the requested delay; or

(2) When an application to create an ADU or JADU is submitted with a permit application to create a new single-family or multifamily dwelling on the lot, the town may delay acting on the permit application for the ADU or JADU until the town acts on the permit application to create the new single-family or multifamily dwelling, but the application to create the ADU or JADU will still be considered ministerially without discretionary review or a hearing.

d. Denial. If the town denies an application to create an ADU or JADU, the town must provide the applicant with comments that include, among other things, a list of all the defective or deficient items and a description of how the application may be remedied by the applicant. Notice of the denial and corresponding comments must be provided to the applicant within the sixty-day time period established by subsection c. above.

e. Appeal of Denial. An applicant may appeal the town's denial of the application by submitting a written appeal to the city clerk. The city council will review the written appeal and affirm or reverse the denial and provide a final written determination to the applicant within sixty business days after receipt of the appeal.

f. Concurrent Review of Demolition. A demolition permit for a detached garage that is to be replaced with an ADU is reviewed with the application for the ADU and issued at the same time.

D. Classes.

1. Class 1: Statutorily Regulated. Class 1 ADUs and JADUs are approved under Government Code Section 66323. If an ADU or JADU complies with each of the general requirements in subsection E. below, it is allowed in each of the scenarios provided in this subsection D.1. An ADU and JADU approved under subsection D.1.a. may be combined with and ADU approved under subsection D.1.b., and ADUs approved under subsection D.1.c. may be combined with ADUs approved under subsection D.1.d.

a. Converted on Lot with Single-Family. One ADU as described in this subsection and one JADU on a lot with a proposed or existing single-family dwelling on it, where the ADU or JADU:

(1) Is either: within the space of a proposed single-family dwelling; within the existing space of an existing single-family dwelling; or (in the case of an ADU only) within the existing space of an accessory structure. Expansions of all existing spaces up to one hundred fifty additional square feet are allowed, and may utilize reduced ADU setbacks, if the expansion is limited to accommodating ingress and egress.

(2) Has exterior access that is independent of that for the single-family dwelling.

(3) Has side and rear setbacks sufficient for fire and safety, as dictated by applicable building and fire codes.

(4) The JADU complies with the requirements of Government Code Sections 66333 through 66339.

b. Limited Detached on Lot with Single-Family. One detached, new-construction ADU on a lot with a proposed or existing single-family dwelling, if the detached ADU satisfies each of the following limitations:

(1) The side- and rear-yard setbacks are at least four feet.

(2) The total floor area is eight hundred square feet of livable space or smaller.

(3) The peak height above grade does not exceed the applicable height limit in subsection E.2. below.

c. Converted on Lot with Multifamily. One or more ADUs within portions of existing multifamily dwelling structures that are not used as livable space, including but not limited to storage rooms, boiler rooms, passageways, attics, basements, or garages, if each converted ADU complies with state building standards for dwellings. Under this subsection D.1.c., at least one converted ADU is allowed within an existing multifamily dwelling, up to a quantity equal to twenty-five percent of the existing multifamily dwelling units.

d. Limited Detached on Lot with Multifamily. No more than two detached ADUs on a lot with a proposed multifamily dwelling, or up to eight detached ADUs on a lot with an existing multifamily dwelling, if each detached ADU satisfies all of the following:

(1) The side- and rear-yard setbacks are at least four feet. If the existing multifamily dwelling has a rear or side yard setback of less than four feet, the town will not require any modification to the multifamily dwelling as a condition of approving the ADU.

(2) The peak height above grade does not exceed the applicable height limit provided in subsection E.2. below.

(3) If the lot has an existing multifamily dwelling, the quantity of detached ADUs does not exceed the number of primary dwelling units on the lot.

2. Class 2: Locally Regulated. Class 2 ADUs are approved under Government Code Sections 66314—66322. Except for class 1 ADUs approved under subsection D.1. above, all ADUs are subject to the standards set forth in [subsection E. below].

E. General Requirements. The following requirements apply to all class 1 and class 2 ADUs and JADUs:

1. Zoning.

a. A class 1 ADU approved under subsection D.1. above may be created on a lot in a residential or mixed-use zone.

b. A class 2 ADU approved under subsection D.2. above may be created on a lot that is zoned to allow single-family dwelling residential use or multifamily dwelling residential use.

c. In accordance with Government Code Section 66333(a), a JADU may only be created on a lot zoned for single-family residences.

2. Height.

a. Detached.

(1) Except as otherwise provided [below], a detached ADU created on a lot with an existing or proposed single-family or multifamily dwelling unit may not exceed sixteen feet in height.

(2) A detached ADU may be up to eighteen feet in height if it is created on a lot with an existing or proposed single family or multifamily dwelling unit that is located within one-half mile walking distance of a major transit stop or high quality transit corridor, as those terms are defined in Section 21155 of the Public Resources Code, and the ADU may be up to two additional feet in height (for a maximum of twenty feet) if necessary to accommodate a roof pitch on the ADU that is aligned with the roof pitch of the primary dwelling unit.

(3) The height of a detached ADU that is at least twenty feet from side and rear property lines, and at least twenty-five feet from all public rights-of-way, may be up to twenty-two feet in height.

(4) A detached ADU created on a lot with an existing or proposed multifamily dwelling that has more than one story above grade may not exceed eighteen feet in height.

b. Attached. An ADU that is attached to the primary dwelling may not exceed twenty-five feet in height or the height limitation imposed by the underlying zone that applies to the primary dwelling, whichever is lower. Notwithstanding the foregoing, ADUs subject to this subsection may not exceed two stories.

c. For purposes of this subsection, height is measured from existing legal grade or the level of the lowest floor, whichever is lower, to the peak of the structure. Existing legal grade means the legally established grade that exists at the time that an application is submitted.

3. Fire Sprinklers.

a. Fire sprinklers are required in an ADU or JADU if sprinklers are required in the primary residence.

b. The construction of an ADU or JADU does not trigger a requirement for fire sprinklers to be installed in the existing primary dwelling.

4. Rental Term.

a. No ADU or JADU may be rented for a term that is shorter than thirty days. This prohibition applies regardless of when the ADU or JADU was created.

b. The renting of the primary dwelling, ADU, or JADU is not considered a business and is not subject to the provisions of Chapter 5.04.

5. No Separate Conveyance. An ADU or JADU may be rented, but except as otherwise provided in Government Code Section 66341, no ADU or JADU may be sold or otherwise conveyed separately from the lot and the primary dwelling (in the case of a single-family lot) or from the lot and all of the dwellings (in the case of a multifamily lot).

6. Septic System. If the ADU or JADU will connect to an onsite wastewater-treatment system, the owner must include with the application a percolation test completed within the last five years or, if the percolation test has been recertified, within the last ten years.

7. Owner Occupancy.

a. ADUs. ADUs are not subject to an owner-occupancy requirement.

b. JADUs.

(1) Generally. As required by state law, JADUs are generally subject to an owner-occupancy requirement. A natural person with legal or equitable title to the property must reside on the property, in either the primary dwelling or JADU, as the person's legal domicile and permanent residence.

(2) Exceptions. The owner-occupancy requirement in this subsection E.7.b. does not apply in either of the following situations:

i. The JADU has separate sanitation facilities (i.e. does not share sanitation facilities with the existing primary dwelling unit structure).

ii. The property is entirely owned by another governmental agency, land trust, or housing organization.

8. JADU Deed Restriction. Prior to issuance of a certificate of occupancy for a JADU, a deed restriction must be recorded against the title of the property in the county recorder's office and a copy filed with the building and planning department. The deed restriction must run with the land and bind all future owners. The form of the deed restriction will be provided by the town and must provide that:

a. The JADU may not be sold separately from the primary dwelling.

b. The JADU is restricted to the approved size and to other attributes allowed by this section.

c. The deed restriction runs with the land and may be enforced against future property owners.

d. The deed restriction may be removed if the owner eliminates the JADU, as evidenced by, for example, removal of the kitchen facilities. To remove the deed restriction, an owner may make a written request of the building and planning department, providing evidence that the JADU has in fact been eliminated. The building and planning department may then determine whether the evidence supports the claim that the JADU has been eliminated. Appeal may be taken from the building and planning department's determination consistent with the other provisions of this code. If the JADU is not entirely physically removed, but is only eliminated by virtue of having a necessary component of an JADU removed, the remaining structure and improvements must otherwise comply with applicable provisions of this code.

e. The deed restriction is enforceable by the director of building and planning or his or her designee for the benefit of the town. Failure of the property owner to comply with the deed restriction may result in legal action against the property owner, and the town is authorized to obtain any remedy available to it at law or equity, including, but not limited to, obtaining an injunction enjoining the use of the JADU in violation of the recorded restrictions or abatement of the illegal unit.

9. Rent Reporting. In order to facilitate the town's obligation to identify adequate sites for housing in accordance with Government Code Sections 65583.1 and 66330, the following requirements must be satisfied:

a. With the building permit application, the applicant must provide the town with an estimate of the projected annualized rent that will be charged for the ADU or JADU.

b. Within ninety days after each January 1 following issuance of the building permit, the owner must report the actual rent charged for the ADU or JADU during the prior year. If the town does not receive the report within the ninety-day period, the owner is in violation of this code, and the town may send the owner a notice of violation and allow the owner another thirty days to submit the report. If the owner fails to submit the report within the thirty-day period, the town may enforce this provision in accordance with applicable law.

c. This requirement shall not be the basis for the delay or denial of an ADU application.

10. Building and Safety.

a. Must Comply with Building Code. Subject to subsection E.9.b. below, all ADUs and JADUs must comply with all local building and fire code requirements.

b. No Change of Occupancy. Construction of an ADU does not constitute a group R occupancy change under the local building code, as described in Section 310 of the California Building Code, unless the building official makes a written finding based on substantial evidence in the record that the construction of the ADU could have a specific, adverse impact on public health and safety. Nothing in this subsection E.10.b. prevents the town from changing the occupancy code of a space that was uninhabitable space or that was only permitted for nonresidential use and was subsequently converted for residential use in accordance with this section.

11. Structures and Equipment within Setbacks. No structures or mechanical equipment may be located within the ADU setback area.

12. Certificate of Occupancy Timing.

a. Generally. No certificate of occupancy for an ADU or JADU may be issued before the certificate of occupancy is issued for the primary dwelling unit.

b. Limited Exception for State-declared Emergencies. Notwithstanding subsection a above, a certificate of occupancy for an ADU may be issued before a certificate of occupancy for the primary dwelling if each of the following requirements are met:

(1) The county is subject to a proclamation of a state of emergency made by the California Governor on or after February 1, 2025.

(2) The primary dwelling was substantially damaged or destroyed by an event referenced in the Governor's state of emergency proclamation.

(3) The ADU has been issued construction permits and has passed all required inspections.

(4) The ADU is not attached to the primary dwelling.

c. Local Exception for detached ADUs. Notwithstanding subsection E.12.a. above, a six-month temporary certificate of occupancy for a detached ADU may be issued before a certificate of occupancy for the primary dwelling if each of the following requirements are met:

(1) The ADU has been issued construction permits and has passed all required inspections.

(2) The ADU is not attached to the primary dwelling.

F. Class 2 ADU Requirements. The following requirements apply only to class 2 ADUs approved under subsection D.2. above. This subsection F. does not apply to class 1 ADUs or JADUs approved under subsection D.1. above.

1. Maximum Size.

a. The maximum size of a detached or attached ADU subject to this subsection F. is as follows:

(1) Eight hundred fifty square feet of livable interior space for a studio or one-bedroom unit; and

(2) One thousand square feet of interior livable space for any unit with two or more bedrooms.

b. An attached ADU that is created on a lot with an existing primary dwelling is further limited to fifty percent of the floor area of the existing primary dwelling.

c. Application of other development standards in this subsection F., such as FAR or lot coverage, might further limit the size of the ADU, but no application of the percent-based size limit in subsection F.1.b. above or of an FAR, front setback, lot coverage limit, or open-space requirement may require the ADU have less than eight hundred square feet of interior livable space.

2. Setbacks.

a. Side and Rear. ADUs that are subject to this subsection F. must conform to four-foot side and rear setbacks.

b. Front. ADUs that are subject to this subsection F. must conform to twenty-foot front setbacks, notwithstanding subsection F.1.c. above.

c. No setback is required for an ADU that is subject to this subsection F. if the ADU is constructed in the same location and to the same dimensions as an existing structure.

3. Lot Coverage. Notwithstanding subsection F.1.c. above, no ADU subject to this subsection F. may cause the total lot coverage of the lot to exceed 50 percent, or to exceed 40 percent in any setback area adjacent to a street line. Lot coverage is calculated in square feet as the sum of all hardscape coverage and structural coverage of a lot. Structural coverage and hardscape coverage are defined and calculated as follows:

a. Structural Coverage. Areas of a lot located beneath a structure having a roof and two or more walls, for example a dwelling, a pool house, or a garage. Structural coverage calculations and maximums are outlined as follows:

Table 17.52.020-1

b. Hardscape.

(1) Hardscape Coverage. Areas of a lot covered by manufactured, non-plant, pervious or impervious material or located beneath a structure with a roof with no more than one wall, for example decking, a concrete slab or walkway, a gazebo.

4. Minimum Open Space. Notwithstanding subsection F.1.c. above, no ADU subject to this subsection F. may cause the total percentage of open space of the lot to fall below fifty percent.

5. Passageway. No passageway is required for an ADU.

6. Parking.

a. Generally. One off-street parking space is required for each ADU or bedroom, whichever is less. The parking space may be provided in setback areas or as tandem parking, as defined above.

b. Exceptions. No parking under subsection F.6.a. is required in the following situations:

(1) The ADU is located within one-half mile walking distance of public transit, as defined above.

(2) The ADU is located within an architecturally and historically significant historic district.

(3) The ADU is part of the proposed or existing primary residence or an accessory structure under subsection D.1.a. above.

(4) When on-street parking permits are required but not offered to the occupant of the ADU.

(5) When there is an established car share vehicle stop located within one block of the ADU.

(6) When the permit application to create an ADU is submitted with an application to create a new single-family or new multifamily dwelling on the same lot, provided that the ADU or the lot satisfies any other criteria listed in subsections F.6.b.(1) through (5) above.

c. No Replacement. When a garage, carport, covered parking structure, or uncovered parking space is demolished in conjunction with the construction of an ADU or converted to an ADU, those off-street parking spaces are not required to be replaced.

7. Architectural Requirements.

a. The materials and colors of the exterior walls, roof, windows, and doors must be the same as those of the primary dwelling.

b. The exterior lighting must be limited to down-lights or as otherwise required by the building or fire code.

c. The ADU must have an independent exterior entrance, apart from that of the primary dwelling.

d. All second-story windows and doors in an ADU less than thirty feet from a property line that is not a public right-of-way shall either be (for windows) clerestory with the bottom of the glass at least six feet above the finished floor, or (for windows and for doors) utilize frosted or obscure glass.

e. An ADU to be constructed on a lot that has an identified historical resource is subject to the ADU exception process.

f. Outdoor showers are not permitted within setback areas and shall not be visible from adjacent properties or the public right-of-way.

g. No roof decks shall be permitted.

h. The interior horizontal dimensions of an ADU must be at least ten feet wide in every direction, with a minimum interior wall height of seven feet.

i. Allowed stories. No ADU subject to this subsection F. may have more than one story, except that an ADU that is attached to the primary dwelling may have more than one story, but shall not exceed twenty-five feet in height, or the maximum height permitted for the primary dwelling in the applicable zoning district, whichever is lower.

j. No window or door of the ADU may have a direct line of sight to an adjoining residential property. Each window and door must either be located where there is no direct line of sight or screened using fencing, landscaping, or privacy glass to prevent a direct line of sight.

k. The ADU and primary dwelling shall use the same driveway to access the street, notwithstanding fire apparatus access standards, as regulated by Central County Fire Department.

8. Landscape Requirements. Except as required in subsection F.8.e. below, evergreen landscape screening must be planted and maintained between an ADU and adjacent parcels and between any public right-of-way and an ADU wall that faces the right-of-way. Screening shall be installed as follows:

a. At least one fifteen-gallon size plant must be provided for every five linear feet of exterior ADU wall. Alternatively, at least one twenty-four-inch box size plant must be provided for every ten linear feet of exterior ADU wall.

b. For a ground-level ADU, plant specimens must be at least six feet tall when installed. As an alternative, for a ground-level ADU, a solid fence of at least six feet in height may be installed.

c. For a second-story ADU, plant specimens must be at least twelve feet tall when installed.

d. All landscaping must be drought tolerant.

e. Notwithstanding any other provision in this code, all landscaping must comply with applicable standards in Title 24 of the California Code of Regulations, including the California Fire Code and California Wildland Urban Interface Code, and any related Central County Fire Department (CCFD) and town regulations. If Title 24 or CCFD regulations prevent landscape screening, the screening required by subsection F.8.a. and F.8.b. and F.8.c. above must be achieved using non-combustible fencing that is consistent with fire-related regulations.

9. Historical Protections. An ADU that is on or within six hundred feet of real property that is listed in the California Register of Historic Resources must be located so as to not be visible from any public right-of-way.

G. Impact Fees. The following requirements apply to all class 1 ADUs and JADUs and class 2 ADUs.

1. School Fees. A JADU or ADU with less than five hundred square feet of interior livable space does not increase assessable space by five hundred square feet for the purposes of Education Code Section 17620(a)(1)(c) and is therefore not subject to school fees under Education Code Section 17620.

2. Other Development Impact Fees.

a. No impact fee is required for a JADU or for an ADU that is less than seven hundred fifty square feet of interior livable space. For purposes of this subsection G.2., "impact fee" means a "fee" under the Mitigation Fee Act (Government Code Section 66000(b)) and a fee under the Quimby Act (Government Code Section 66477). "Impact fee" here does not include any connection fee or capacity charge for water or sewer service.

b. Any impact fee that is required for an ADU that is seven hundred fifty square feet or more of interior livable space must be charged proportionately in relation to the square footage of the primary dwelling unit (e.g. the floor area of the ADU, divided by the floor area of the primary dwelling, times the typical fee amount charged for a new dwelling).

H. Nonconforming Zoning Code Conditions, Building Code Violations, and Unpermitted Structures.

1. Generally. The town will not deny an ADU or JADU application due to a nonconforming zoning condition, building code violation, or unpermitted structure on the lot that does not present a threat to the public health and safety and that is not affected by the construction of the ADU or JADU.

2. Unpermitted ADUs and JADUs Constructed Before 2020.

a. Permit to Legalize. As required by state law, the town may not deny a permit to legalize an existing but unpermitted ADU or JADU that was constructed before January 1, 2020, unless denial is based on either of the following grounds:

(1) The ADU or JADU violates applicable building standards; or

(2) The ADU or JADU does not comply with state ADU or JADU law or this ADU ordinance (Chapter 17.52).

b. Exceptions.

(1) Notwithstanding subsection H.2.a. above, the town may deny a permit to legalize an existing but unpermitted ADU or JADU that was constructed before January 1, 2020, if the town makes a finding that correcting a violation is necessary to comply with the standards specified in California Health and Safety Code Section 17920.3.

(2) Subsection H.2.a. above does not apply to a building that is deemed to be substandard in accordance with California Health and Safety Code Section 17920.3.

3. Encouragement of ADU Establishment in Existing Residential Livable Spaces and Domestic Units. Recognizing that there may be a considerable existing stock of potential ADUs in the town representing a valuable housing resource for the community, including guest suites, guest quarters, pool houses, carriage houses, domestic quarters, and similar spaces, the town encourages property owners to apply to establish an ADU or JADU within existing space in accordance with this chapter.

a. No Penalty for Seeking Legalization. Upon receipt of an application to legalize an unpermitted ADU or JADU described in subsection H., the town shall not penalize the applicant solely for having established the unpermitted or nonconforming unit.

b. Existing Detached Domestic Units—Legal Nonconforming Status.

(1) A detached domestic unit that was lawfully established and existing as of January 10, 1983, is deemed a legal nonconforming accessory structure.

(2) Detached domestic unit means living quarters designed, capable of being used, or intended to be used to house household help, such quarters being not structurally attached to the single-family dwelling served by the household help.

(3) Except as provided in subsection H.3.c. below, alterations to a legal nonconforming detached domestic unit that is not being permitted as an ADU shall be confined to the interior of the structure; exterior improvements shall be limited to normal upkeep and repair and to improvements that do not enlarge or alter the existing exterior dimensions of the structure.

c. Establishing an ADU Within Existing Residential Livable Space or an Existing Accessory Structure.

(1) An applicant may apply to permit and legalize an ADU or JADU within existing space of a primary dwelling or within an existing accessory structure, including an existing detached domestic unit.

(2) When an existing detached domestic unit or other existing space is proposed to be established as an ADU, the town shall not require correction of unrelated nonconforming zoning conditions, building code violations, or unpermitted structures found elsewhere on the lot that are not impacted by the ADU and do not pose a threat to public health and safety.

(3) Improvements to an existing structure in connection with establishing an ADU may include those alterations necessary to comply with applicable building standards and this chapter. Any expansion beyond the existing structure shall be regulated by Chapter 17.52 and applicable state law.

d. Disaster Reconstruction. If a natural disaster (such as a fire, earthquake, flood, landslide, etc.) damages or destroys an existing detached domestic unit or other existing accessory structure that is proposed to be established as an ADU, the structure may be reconstructed in the same location and to the same or smaller exterior dimensions as the damaged or destroyed structure, consistent with this chapter and applicable state law.

(Ord. No. 800, § 4(Exh. A), 4-13-2026)

A. Exceptions Allowed. Any proposed ADU or JADU that would otherwise be allowed under this chapter but does not conform to the objective design to development standards set forth in this chapter may be allowed by the town following design review as prescribed by Chapter 2.12 of this code.

B. Discretionary Design Review. An ADU or JADU application submitted under this Section 17.52.030 will be considered, reviewed, and noticed as a "type B project" under Section 2.12.070.A.

C. Findings Required. The following findings shall be made in advance of any approval of an ADU or JADU Exception:

1. The project is consistent with the town general plan.

2. The project is consistent with this code, including the town zoning ordinance.

3. The project is consistent with the town residential design guidelines.

4. The project is consistent with all other town land use policies and plans.

5. The project has undergone the design review process outlined in Chapter 2.12 of this code.

6. The project has been publicly noticed as a "type B project" under Section 2.12.070.A of this code.

7. The project does not constitute a risk to the welfare of the town and its residents.

8. The project does not constitute a risk to the health and safety of the town and its residents.

(Ord. No. 800, § 4(Exh. A), 4-13-2026)