This Section is intended to comply with State Law (including, but not limited to, California Government Code Sections 65852.2 and 65852.22 et seq.), by allowing accessory dwelling units (ADU) and junior accessory dwelling units (JADU) through ministerial review, subject to meeting the standards prescribed below. In the event of any conflict or inconsistency between this Section and State law or other Sections in the Municipal Code, the more permissive regulations shall prevail.

(Ord. No. 1447, § 10, 7-19-2023)

A.

Any ADU may be permitted:

1.

On any lot zoned for a residential use, or any non-residentially zoned lot which is currently occupied with a single-family dwelling or multiple-family dwelling.

2.

On any lot zoned or occupied by a religious institution, as defined in Chapter 22.04.

B.

ADUs shall not be located in the following locations:

1.

In areas encumbered by a recorded easement, including but not limited to, public utility easements, conservation easements, access easements, pedestrian pathway easements and open space easements; or

2.

In areas that extend into a creek bank.

(Ord. No. 1447, § 10, 7-19-2023; Ord. No. 1463, § XVII, 10-23-2024)

The following number of ADUs and JADUs shall be the maximum number of accessory units permitted on lots subject to this Section.

A.

Lot with one single-family dwelling: one ADU and one JADU.

B.

Lot with more than one legal, conforming single-family dwelling: one ADU total and one JADU.

C.

Lot with an existing multiple-family dwelling, either:

1.

Up to eight detached ADUs, but shall be limited to the number of existing multifamily units on the lot; or

2.

At least one ADU converted from non-habitable portions of the existing primary structure that are not within the living space of a dwelling unit (e.g., basement, attic, garages storage room). The maximum number of ADUs converted from portions of the existing primary structure that are not within the living space of a dwelling unit shall not exceed 25 percent of the total number of existing dwelling Units on the lot.

D.

Lot with a proposed multiple-family dwelling:

1.

Up to two detached ADUs.

E.

Lot with religious institution: up to two ADUs, subject to the following exceptions:

1.

When a lot contains a religious institution and a single-family and/or multiple-family dwelling, the maximum number of ADU(s) permitted shall be associated with only one of the uses, whichever permits more.

2.

When a religious institution occupies multiple lots, only one of these lots shall be eligible for the ADU(s).

(Ord. No. 1447, § 10, 7-19-2023; Ord. No. 1463, § XVII, 10-23-2024; Ord. No. 1469, § IX, 4-2-2025)

A.

Minimum Size. An ADU/JADU shall be a minimum of 150 square feet or the size necessary to accommodate an efficiency unit as defined by California Health and Safety Code Section 17958.1, whichever is greater.

B.

Maximum Size.

1.

ADU. The total floor area of an attached or detached ADU shall not exceed 1,200 square feet, excluding any garage area. In no case shall an ADU attached to the primary dwelling exceed 50 percent of the existing primary dwelling square footage, except a State Exemption ADU shall be permitted.

2.

JADU. The total floor area of a JADU shall not be more than 500 square feet, excluding any shared sanitation facility within the primary dwelling structure.

C.

Conversion Restrictions. A JADU created entirely through conversion of an existing permitted structure is allowed a physical addition of no more than 150 square feet and shall be limited to accommodating ingress and egress, subject to all other applicable provisions of this Chapter. The conversion of an existing permitted accessory structure or a portion of an existing primary structure to an ADU is not subject to unit size requirements.

D.

Lot Coverage and Floor Area Ratio. Newly constructed ADUs shall be exempt from the maximum lot coverage or floor area ratio allowed in the zoning or overlay district.

(Ord. No. 1447, § 10, 7-19-2023)

A.

Front. Both attached and detached ADUs shall be subject to the same front setback requirements as the primary dwelling.

B.

Side. A setback of no less than four feet from the side lot line shall be required for either an attached or detached ADU.

C.

Rear. A setback of no less than four feet from the rear lot line shall be required for either an attached or detached ADU.

D.

Expansion of Converted Existing Structures. The first floor of an existing permitted structure which has setbacks of less than four feet and is planned for conversion into an ADU can be expanded, so long as the expansion does not result in additional encroachment into the required setbacks.

E.

Architectural Features. Architectural features including sills, eave overhangs, awnings, and cornices may extend into a required setback or space between buildings not more than 18 inches.

(Ord. No. 1447, § 10, 7-19-2023)

A.

Non-state Exemption ADU. For any detached ADU which does not qualify as a State Exemption ADU, the distance between the ADU and any other structures shall be at least five feet.

B.

State Exemption ADU. Detached ADUs located closer than five feet to any other structures without an automatic residential fire sprinkler system shall be subject to a minimum of one-hour fire-resistance rating and shall comply with all California Building Code and California Fire Code fire-rating requirements.

(Ord. No. 1447, § 10, 7-19-2023)

Building height shall be measured as the vertical distance from any point on the natural grade, to the topmost point of the building immediately above.

A.

Detached ADU.

1.

New Construction. A maximum height of 18 feet for a new detached ADU shall be permitted. An additional two feet in height to accommodate a roof pitch on the ADU that is aligned with the roof pitch of the primary dwelling unit shall also be permitted.

2.

Addition to an Existing Detached Structure. An ADU which results in an addition to an existing detached structure that is not the primary dwelling shall have a maximum height of 25 feet or the height limitation associated with the primary dwelling, whichever is lower, and shall not exceed two stories. A detached ADU shall be either a one-story structure or second-story addition to an existing legal structure.

B.

Attached ADU. A maximum height of 25 feet or the height limitation associated with the primary dwelling, whichever is lower, shall be permitted for an ADU that is attached to a primary dwelling.

(Ord. No. 1447, § 10, 7-19-2023)

A.

Minimum Parking. A minimum of one independently usable off-street parking space shall be provided for each ADU, which shall be provided in addition to the required parking for the primary residential dwelling(s), except as outlined in Subsections C and D. No parking is required for a JADU.

B.

Parking Design. This space need not be covered, and shall comply with all development standards set forth in Chapter 22.36 (Off-Street Parking and Loading Facilities), except the space may be compact and/or uncovered. A tandem parking space may also be used to meet the parking requirement for an ADU, providing such space will not encumber access to a required parking space for the primary single-family dwelling.

C.

Replacement Parking. When a garage, carport, or covered parking structure is demolished or converted in conjunction with the construction of an ADU or JADU, no parking replacement spaces for the primary residence shall be required. Any other required off-street parking spaces shall be maintained for the primary residence, and may be located in any configuration on the same lot as the ADU, including, but not limited to, as covered spaces, uncovered spaces, or tandem spaces, or by the use of mechanical automobile parking lifts. A demolition permit for a detached garage that is to be replaced with an accessory dwelling unit shall be reviewed with the application for the accessory dwelling unit and issued at the same time. The applicant is not required to provide written notice or post a placard for the demolition of a detached garage, that is to be replaced with an accessory dwelling unit, unless the property is located within the Historic Overlay District or another architecturally and historically significant historic district.

D.

Parking Exceptions. Off-street parking shall not be required for an ADU in any of the following instances:

1.

The ADU is a Studio Unit.

2.

The ADU is located within one-half mile walking distance of public transit, including various means of transportation that charge set fees, run on fixed schedules, and are available to the public.

3.

The ADU is located within the Historic Overlay District or another architecturally and historically significant historic district.

4.

The ADU is part of the proposed or existing primary dwelling or an accessory structure.

5.

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

6.

When there is a designated pick-up or drop-off location for car share vehicles located within one block of the ADU.

7.

The ADU is consistent with affordability requirements outlined in Section 22.43.140.

(Ord. No. 1447, § 10, 7-19-2023)

A.

Aesthetics. The design of the ADU and/or JADU shall be as follows:

1.

For a detached ADU, the exterior materials and design shall match the design of any existing primary unit on the property through the use of the same exterior wall materials, identified color tones, window types, door and window trims, roofing materials and roof pitch. The Planning Manager or designee may determine without the requirement for a public hearing or a public review process that similar materials substantially comply with this requirement.

2.

For an attached ADU, the exterior materials, windows, and other architectural features shall match the existing structure by employing the same building form, exterior wall materials, color tones, window design, door and window trims, roofing materials and roof pitch.

B.

Lighting. Exterior building lighting shall be fully shielded and downward-facing and limited to one exterior light fixture per exterior doorway, or the minimum necessary to comply with the California Building Standards Code.

C.

Utility Connections. All electrical and utility services to a new dwelling unit shall be undergrounded.

(Ord. No. 1447, § 10, 7-19-2023)

A.

ADUs and JADUs shall have an independently accessible entrance that does not require passage through the primary residence.

B.

With the exception of JADUs, attached ADUs shall not be allowed a connecting doorway or other permanent ingress or egress between the primary dwelling and the ADU.

C.

Unless it would preclude the development of a Statewide Exemption ADU, an exterior stairway proposed to serve an ADU or JADU on a second story or higher shall not be visible from the public right-of-way. Access to a first story dwelling by stairs or ADA accessible ramp may be permitted in the front of the primary dwelling.

D.

A JADU created entirely through conversion of an existing permitted structure is allowed a physical addition of no more than 150 square feet and shall be limited to accommodating ingress and egress consistent with the remainder of this Chapter.

(Ord. No. 1447, § 10, 7-19-2023)

A.

Windows. ADUs that do not meet the setback requirements that would apply to a primary dwelling in the same district shall require windows that face neighboring property lines to:

1.

Be clerestory with a minimum sill height of six feet above the subject interior floor elevation; or

2.

Have frosted or opaque glass and not be operable.

B.

Balconies and Decks. Balconies and decks attached to ADUs shall comply with the setback requirements that apply to a primary dwelling in the same district.

(Ord. No. 1447, § 10, 7-19-2023; Ord. No. 1458, § XII, 5-15-2024)

A.

Compliance with Building Codes. All ADUs and JADUs shall comply with all applicable requirements of the building code as adopted and enforced at time of submitting a complete application. In cases where an ADU or JADU is to be created through the reconfiguration of a portion of an existing single-family dwelling, both the secondary and primary dwelling shall be upgraded to comply with such building code requirements, which include but is not limited to noise separation between units sharing common walls, emergency egress and heating/ventilation requirements, as required by the Chief Building Official or designee.

B.

Permanent Foundation. A permanent foundation shall be required for all attached and detached ADUs and for any ADU or JADU created entirely through conversion to the existing structure with a physical addition.

C.

Public Utilities and Services. ADUs shall be served by public water and sewer and shall have access to an improved public street.

D.

Required Facilities. With the exception of JADUs, all attached or detached ADUs must include:

1.

Independent facilities for living, sleeping, cooking, and sanitation.

2.

A kitchen area containing a refrigerator, sink, and permanently installed cooking appliance, which must include at least a fixed stovetop.

3.

A fully plumbed bathroom including sink, shower, and toilet.

4.

If a permitted JADU does not include a separate bathroom, the JADU must include a separate entrance from the main entrance to the structure, with an interior entry to the main living area.

E.

Fire Sprinklers. All newly constructed or converted ADUs are required to have automatic residential fire sprinklers consistent with California Residential Code Section R313.2, unless the existing primary structure was constructed prior to the requirement for automatic residential sprinkler system. The construction of an accessory dwelling unit shall not trigger a requirement for fire sprinklers to be installed in the existing primary dwelling.

F.

Windows. Detached ADUs with a wall(s) located closer than five feet to a primary dwelling shall not include any openings such as windows or doors on the subject wall(s).

G.

Occupancy. ADUs and JADUs may be rented separately from the primary dwelling—Dwellings with ADUs do not require owner occupancy of either the primary dwelling or ADU. Dwellings with JADUs require owner occupancy of either the primary dwelling or the JADU, but shall not be required if the owner is another governmental agency, land trust, or housing organization. No ADU or JADU shall be rented for a period of less than 31 days and cannot be occupied as a short-term rental unit.

H.

Conveyance. ADUs may be separately conveyed as condominiums under the following requirements.

1.

Non-Profit Conveyance: The involvement of qualified nonprofit housing organizations consistent with California Government Code Sections 65852.2 and 65852.26.

2.

Private Conveyance: An attached ADU may be conveyed separately from a primary dwelling via a private transaction with implementation of a condominium plan. The conveyance of the ADU shall also comply with Government Code Section 65852.2, the Subdivision Map Act (Division 2 (commencing with Section 66410)), and all objective requirements of Martinez Municipal Code Title 21.

I.

Common Sanitation Facilities. JADUs are permitted to have common sanitation facilities with the primary dwelling. Any JADU with common sanitation facilities shall have interior access to the primary dwelling.

J.

Protected Trees. Where an ADU is proposed within the dripline of a protected tree, as defined in Section 8.08.044, an arborist report prepared by a licensed arborist shall be required and all ensuing recommendations shall be followed.

K.

Hillside Properties. For areas with slopes greater than 30 percent, the preparation of a geotechnical investigation report shall be required and all ensuing recommendations shall be followed.

(Ord. No. 1447, § 10, 7-19-2023; Ord. No. 1458, § XII, 5-15-2024)

A.

Exceptions May Be Granted. The Zoning Administrator may grant an exception to height, size, setback, building separation, parking, ingress and egress, privacy, and design standards consistent with the procedures set forth in Section 22.06.020 and subject to the following findings:

1.

The project will substantially comply with the Zoning Ordinance and the purpose and intent of the zoning district where the property is located.

2.

The project will not pose a detrimental impact to the site, adjacent properties, or neighborhood.

3.

The project will otherwise comply with applicable Zoning Ordinance standards and requirements.

B.

Limitations of This Section. Consistent with California Government Code Section 65852.2, this Section shall not preclude or impede the development of any Statewide Exemption ADU and in compliance with all other local development standards.

(Ord. No. 1447, § 10, 7-19-2023)

A.

Applicability. Applicants that are proposing to deed-restrict an ADU to the following affordability levels are eligible for the bonuses described below:

1.

Moderate-Income, deed-restricted: Provide affordability between 80 to 120 percent of area median income with affordability restrictions in place for 55 years.

2.

Lower-Income, deed-restricted: Provide affordability at less than 80 percent of area median income with affordability restrictions in place for 35 years.

B.

Bonuses. The Planning Manager or designee shall approve the following exceptions:

1.

For ADU(s) consistent with the affordability requirements outlined in subsection A:

a.

If the project is located in within a Transit Priority Area, defined by California Public Resources Code Section 21099(a)(7) as an area within one-half mile of a major transit stop that is existing or planned, the applicant shall be allowed one additional unrestricted ADU for every deed-restricted ADU with no limits so long as the respective amount of deed-restricted ADUs is provided, subject to space limitations and compliance with other standards and requirements of this chapter.

b.

If the project is not located within a Transit Priority Area, the limit shall be one deed-restricted and one additional unrestricted ADU, for a maximum of three ADUs.

2.

Waiver from another development standard listed in this chapter that would otherwise make development of a deed-restricted ADU infeasible.

C.

Requirements. Property owners shall work with the City and Housing Authority of the County of Contra Costa (HACCC) to establish an affordable housing program, which at a minimum shall establish tenant eligibility, income verification and reporting requirements, and procedures for when a tenant's income raise beyond income limits.

(Ord. No. 1447, § 10, 7-19-2023; Ord. No. 1463, § XVII, 10-23-2024)

An application for an ADU or JADU shall be allowed with a building permit. In addition to the normal building permit submittal requirements, a completed application must include, at a minimum:

A.

Site Plan.

1.

Drawn to scale.

2.

Dimensions of the perimeter of parcel on which the proposed dwelling will be located.

3.

Indicate the location and dimensioned setbacks of all existing, proposed, and adjacent structures abutting the project site.

4.

Data on the floor space of the existing structure(s) and proposed unit.

5.

All easements, building envelopes, and special requirements of the subdivision as shown on the final map and improvement plans shall be included.

6.

Provide average slope calculations for the project site.

7.

Calculations indicating the square footage of the structure and the lot, including calculations on the plan for the percentage of lot area covered by the foundation of the existing and proposed dwelling units.

B.

Floor Plans.

1.

Each floor and room shall be dimensioned, and the resulting floor area calculation included.

2.

The use of each room shall be identified.

3.

The size and location of all windows and doors shall be clearly depicted.

C.

Elevation Views.

1.

Provide north, south, east, and west elevations.

2.

Show all heights for all existing and proposed structures on site. Height shall be calculated as the vertical distance of a building at any point, within a given plane, from finished grade to the top of the roof or parapet walls.

3.

Show all openings, exterior finishes, original and finish grades, stepped footing outline, roof pitch, and materials.

4.

For ADUs and/or JADUs that include modifications to the exterior of the primary structure or new construction, provide elevations showing all openings, exterior finishes, original and finish grades, stepped footing outline, roof pitch, materials and color board for the existing primary structure and the proposed unit.

(Ord. No. 1447, § 10, 7-19-2023)

A.

Application to be Administratively Approved. All ADUs and JADUs require a building permit. The building permit will be reviewed for compliance with applicable building codes, California Government Code Section 65852.2 and 65852.22, and development and design standards from this Section. If an application to create an ADU or JADU is submitted as part of a project that requires discretionary review, a Building Permit shall not be issued for the ADU or JADU until the discretionary approval(s) has/have been granted and any applicable appeal periods have expired.

B.

Approval of Preapproved ADU. The City shall approve or deny an application for an ADU ministerially within 30 days if the proposed ADU plans utilize either preapproved project plans provided on the City's website or if the plans are identical to a separate and previously approved application.

C.

Approval of Unit Does Not Permit Land Division. Approval of an ADU or JADU shall not be deemed to be a division of land for purposes of California Government Code Section 66410 et seq. or Title 21 of the Municipal Code, nor shall the administrative approval above entitle the applicant to either: (a) such a division of land; or (b) to have each of the dwelling units on the parcel separately assessed for property tax purposes.

(Ord. No. 1447, § 10, 7-19-2023; Ord. No. 1458, § XII, 5-15-2024)

See Chapter 15.55 (Residential Amnesty Program for Unpermitted Dwelling Units) for regulations related to legalizing unpermitted dwelling units.

(Ord. No. 1469, § IX, 4-2-2025)

Editor's note— Ord. No. 1469, § IX, adopted April 2, 2025, set out provisions intended for use as § 22.43.160. Inasmuch as there were already provisions so designated, said ordinance has been codified herein as § 22.43.170 at the discretion of the editor.