Mountain House Municipal Code Ch. 14 Residential Accessory Dwelling Units

The intent of this Chapter is to provide a method for increasing affordable housing opportunities by providing opportunities for new Accessory Dwelling Units (ADUs) and Junior ADUs (JADUs) consistent with state law. ADUs and JADUs are intended to provide independent living units for family members, students, the elderly, in-home health and childcare providers, and others within existing residential neighborhoods. All new ADUs and JADUs must be located, developed, and operated in compliance with the Chapter and Division 3, Residential Zones.

(Ord. 2024-18, § 1(Exh. A), 2024)

One (1) ADU may be constructed on a lot in any zone which allows a single-family dwelling as a permitted use. One (1) JADU may be constructed on a lot in any zone permitting a single-family residential use type. Multiple converted or detached ADUs may be constructed on a lot with an existing multi-family use, where consistent with Government Code Sections 65852.2(e)(1)(C) and (D).

(a) Types of ADUs Allowed. The types of ADUs allowed include an attached ADU, detached ADU, converted ADU, interior ADUs, or junior ADU. They may be within existing dwelling units, garages, storage areas, or similar areas or an accessory structure attached or detached from the proposed or existing primary dwelling unit and located on the same lot as the proposed or existing primary dwelling.

(b) Relation to Primary Dwelling Unit. The ADU shall be clearly subordinate to the primary dwelling unit on the lot with regard to size, location and appearance. Detached or attached accessory dwelling units shall have exterior walls and roofs that are consistent with the primary dwelling unit and incorporate the same or similar building materials, colors, and exterior surfaces and finishes as those on the primary dwelling unit.

(c) Relation to General Plan and Zoning Density Limits. An ADU that conforms to the standards of this Chapter shall be deemed to be an accessory use or an accessory building and shall not be considered to exceed the allowable density for the lot upon which it is located and shall be deemed to be a residential use that is consistent with the General Plan and zoning designations for the lot. The ADU shall not be considered in the application of any County ordinance, policy, or program to limit residential growth except where water or sewer system capacity constraints have been identified by the Department of Public Works.

(d) Permanent Address. The property owner shall obtain an approved permanent address for an ADU and JADU.

(e) Availability of Water and Sewer Service. Prior to issuance of a building permit for an ADU, the property owner must confirmation that adequate water and wastewater disposal service is available, either from a service provider or from a well and on-site septic system, to the Director. The County has identified certain areas, shown in Figure 9-8-1401.2(e) where capacity constraints in the local sewer collection system. In these areas, a determination of adequate water and sew collection for the proposed ADU by the Department of Public Works is required.

FIGURE 9-8-1401.2(E)

[Figure]

(f) Fees. The property owner of an ADU or JADU shall be subject to the payment of all sewer, water, and other applicable fees, except as specifically provided in Government Code Sections 65852.2 and 65852.22. No impact fee shall be charged for development of an ADU less than seven hundred fifty (750) square feet in size. In this context, the term "impact fee" does not include any connection fee or capacity charge established by the City or other local agency, special district, or water corporation.

(g) ADUs Subject to Flood Hazards. All ADUs located in a floodplain designated pursuant to Chapter 2 of Division 16, Flood Haza comply with the provisions of that Chapter.

(h) Sprinklers. ADUs are not required to provide fire sprinklers unless sprinklers are required for the primary residence.

(i) Restrictions. All ADUs and JADUs are subject to the following restrictions:

(1) The development and use of the ADU or JADU shall only be valid and permitted based on the terms established in this Chapter.

(2) Prior to issuance of a building permit for an ADU or JADU, the property owner shall record a deed restriction with the County Recorder's Office and provide a copy of the stamped deed restriction to the Community Development Department, including the following restrictive covenants:

(A) The ADU or JADU shall not be sold separately from the primary residence;

(B) The ADU or JADU is restricted to the maximum size allowed by Chapter 14 of Division 8, Residential Accessory Dwelling Units or as approved by an ADU Permit;

(C) The property owner and all successors in interest in the property shall respond to the City's periodic surveys of owners of ADU and JADUs for reporting purposes to the State Department of Housing and Community Development; and

(D) If the ADU or JADU is rented, it shall not be rented for a period of less than thirty (30) consecutive days.

(Ord. 2024-18, § 1(Exh. A), 2024)

(a) Detached and Attached ADUs. An ADU permit is required for the construction of an attached or detached ADU unless:

(1) The ADU is a detached structure no more than sixteen (16) feet high that has a floor area no greater than eight hundred (800) square feet and maintains a minimum four-foot side and rear yard setback; or

(2) The ADU is on a lot with an existing legal multi-family residential use.

(3) Detached and attached ADUs that do not require an ADU permit must submit a building permit application and an ADU Checklist to the Community Development Department to ensure that the standards of this Chapter are met. The Department shall not issue a building permit without an approved ADU Checklist.

(b) Interior ADUs and JADUs. No ADU permit is required for an interior ADU and a JADU if the proposed unit meets the following requirements and the standards of this Chapter and a building permit is obtained:

(1) The unit will be contained within an existing structure or if in an existing accessory structure, it does not require an increase in the floor area of more than twenty percent (20%) or one hundred fifty (150) square feet, whichever is greater.

(2) The unit has exterior access from a public right-of-way that is independent from the existing residence. This access may be provided through a front yard, side yard, or rear yard.

(3) JADUs Only: The owner of the JADU must occupy either the JADU or the remaining portion of the single-family residence.

(c) Other Required Permits and Approvals. Projects that are exempt from obtaining an ADU Permit are still subject to applicable permit requirements and approvals, including, but not limited to, building permits, grading permits, encroachment permits, home occupation permits, flood variances, if required, sanitation permits, well permits, and other construction-related permits and approvals. The County shall not final building permits for an ADU or JADU before it finals building permits for the primary dwelling.

(Ord. 2024-18, § 1(Exh. A), 2024)

Applications for ADU Permits may be initiated by the property owner or the property owner's authorized agent by submitting a permit application and an ADU Checklist to the Community Development Department. Applications shall be filed with the Community Development Department, and the Director shall ministerially approve an ADU Permit application, provided the application is complete and demonstrates that the proposed ADU complies with all of the requirements in this Chapter. No public hearing is required. A fee, as specified by resolution of the City Council, shall be required. All of the following minimum requirements shall be met when filing an application for an ADU Permit:

(a) Existing Residence. There shall be no more than one (1) existing single-family dwelling on the property.

(b) Owner Occupancy—JADUs Only. The owner of the property shall occupy either the existing single-family dwelling or the proposed JADU for a period exceeding ninety (90) days per year.

(c) Number of Units. There shall be no more than one (1) ADU and one (1) JADU per lot in the R-R, R-VL, and R-L Residential zones and in the AG, AL, and AU Agricultural zones.

(Ord. 2024-18, § 1(Exh. A), 2024)

ADU applications shall be reviewed ministerially by the Director using the Staff Review Procedure in Chapter 3 of Division 2.

(a) The Director shall act on an ADU Permit application within sixty (60) calendar days from the date the City receives a complete application provided there is an existing single-family or multifamily dwelling on the lot.

(b) If the permit application to create an ADU or a JADU is submitted with a permit application to create a new single-family dwelling on the lot, the City may delay acting on the permit application for the ADU until it acts on the permit application to create the new single-family dwelling, but the ADU Permit application shall still be considered ministerially without discretionary review or a public hearing.

(c) If the applicant requests a delay, the 60-day time period shall be tolled for the period of the delay.

(d) If the local agency has not acted upon the complete application within sixty (60) days, the application shall be deemed approved.

(Ord. 2024-18, § 1(Exh. A), 2024)

All ADU Permits and building permits for ADUs approved under the provisions of this Chapter are subject to the following development standards:

(a) Size of Unit. The ADU shall conform to the following requirements:

(1) Except as provided in Subsection (a)(2), the ADU shall not exceed one thousand two hundred (1,200) square feet and have no more than two (2) bedrooms.

(2) If there is an existing primary dwelling, an attached ADU shall not exceed fifty percent (50%) of the gross floor area of the primary dwelling.

(3) An ADU with fewer than two bedrooms is limited to eight hundred and fifty (850) square feet of floor area.

(b) Height. An attached ADU or detached ADU shall not exceed sixteen (16) feet in height, or when more than fifty percent (50%) of the floor area of an ADU is located above an existing or proposed garage, the entire combined structure (the garage plus the ADU) shall not exceed twenty-five (25) feet in height.

(c) Location. Detached ADUs shall be separated from the primary dwelling and any accessory structures on the lot by the minimum distance required by the Building Code.

(d) Setbacks. No setback shall be required for an interior ADU or converted ADU, and a setback of no more than four (4) feet from the side and rear lot lines shall be required for an ADU that is not converted from an existing structure or a new structure constructed. The ADU shall comply with all other yard requirements for an accessory building in the zone as well as the following requirements:

(1) Except as provided in Subsection (d)(2), the ADU shall not extend beyond the front of the primary single-family dwelling.

(2) In areas zoned R-R and in Agricultural zones where ADUs are allowed, the ADU may extend beyond the front of the primary single-family dwelling, provided it does not extend into the front yard setback.

(3) For the purpose of this Section, the front of the primary single-family dwelling is defined as that part of the primary single-family dwelling that is nearest to the front yard setback.

(e) Lot Coverage. An ADU will not be required to conform to the lot coverage standard of the zone where the ADU will be located if application of the coverage standard would violate Government Code Section 65852.2(c)(2)(C) and not allow an eight hundred (800) square foot ADU that is sixteen (16) feet in height with four-foot side and rear yard setbacks.

(f) Building Plans.

(1) An ADU shall include provisions for living, eating, cooking, sleeping, and sanitation including a closet or other reasonable storage.

(2) All ADUs shall be designed to be similar in materials, color, style and form to the primary dwelling. Exterior architectural details, including windows, roof pitch, and trim, shall be similar to the primary dwelling.

(3) All exterior lighting, including landscape lighting, shall be shielded or directed so that it does not create glare off-site or illuminate the primary dwelling or adjacent property.

(4) For privacy and security, windows in ADUs that are within fifteen (15) feet of a side or rear lot line shall be located to avoid line of sight to windows of habitable rooms on adjacent properties. Obscured glass and other techniques may be used to avoid line of sight.

(5) An ADU shall have separate exterior access. The exterior access shall be a standard exterior door that is located where it preserves, to the greatest extent feasible, the privacy of the primary dwelling and adjoining residences.

(6) A permanent foundation is required for all ADUs.

(g) Off-Street Parking. Off-street parking shall be provided as required by Chapter 2 of Division 10. The minimum parking requirement for an ADU shall be one (1) parking space. This space may be provided as tandem parking on an existing driveway or in area. No parking shall be required for a JADU, and no additional parking shall be required if the ADU is located: (1) one-half (½) mile of public transit; (2) in an historic district designated by the City; (3) in part of an existing primary res an existing accessory structure; (4) in an area requiring on-street parking permits but they are not offered to the accessory dwelling unit; or (5) within one (1) block of a car-share pick up/drop-off location. When a garage, carport, or covered parking structure is demolished in conjunction with the construction of an ADU or converted to an ADU, the parking provided by the garage, carport or covered parking structure does not have to be replaced.

(h) Common Driveway. Except in Agricultural and R-R zones, the ADU shall be accessed by a common driveway serving both the ADU and the existing or proposed single-family residence and having a single access point or by a circular driveway with two (2) access points.

(i) Sewer and Water.

(1) Both the proposed ADU and the existing single-family dwelling shall have public sewage and water pservice.

(j) Other Codes. The ADU shall conform with all the requirements of the Environmental Health Division that are applicable to residential units in the zone in which the property is located. All ADUs must satisfy building, fire, and safety standards, such as fire lane widths, minimum fire flows, and emergency egress, as established through State of California's Fire and Building Codes and as amended by the City.

(k) Requirements for Manufactured Homes. If the ADU is a manufactured home, it shall be installed on a permanent foundation, and the following additional requirements shall apply:

(1) No permanent room additions shall be allowed, but patio covers constructed of the same materials as the manufactured home shall be permitted; and

(2) Skirting constructed of the same materials as the manufactured home shall be installed.

(l) Supplemental Standards for Attached ADUs.

(1) An attached ADU must share at least one (1) common wall or roofline with the living area of the principal dwelling.

(2) An attached ADU shall have a separate entrance, located on the side or the rear of the ADU; provided, however, that in no event shall any external stairwell be placed within the side yard setback.

(m) Supplemental Standards for JADUs.

(1) No JADU shall contain more than five hundred (500) square feet of floor space. A JADU shall be contained entirely within an existing single-family dwelling. An efficiency unit (a single room that includes sleeping and kitchen function) shall not contain less than one hundred fifty (150) square feet of floor space, exclusive of a bathroom.

(A) A JADU must be created within the existing walls of an existing single-family dwelling and must include conversion of an existing bedroom or other space within the dwelling to habitable space.

(B) A separate exterior entry shall be provided to serve a JADU.

(C) The JADU shall include an efficiency kitchen with a sink, a cooking appliance and refrigeration facilities, a food preparation counter, and storage cabinets.

(D) Access to a bathroom is required, which may be part of the JADU or located in the existing primary dwelling. If provided as part of the primary dwelling, the JADU shall have direct access to the main living area of the primary dwelling so as not to need to go outside to access bathroom.

(E) No additional parking is required for a JADU.

(2) Supplemental Standards for Detached ADUs.

(A) The distance between the principal dwelling and a detached ADU must be the minimum distance required by the Building Code.

(B) A detached accessory structure legally in existence prior to the effective date of this Section and located outside of the front yard setback, may be converted into an accessory dwelling unit, regardless of any existing nonconformity as to side setback, rear setback, or height if:

(i) The existing structure is not modified or added to in any way that increases the level of nonconformity with all applicable regulations in Title 9;

(ii) The floor area of the resulting ADU does not exceed one thousand two hundred (1,200) square feet; and

(iii) The minimum parking requirements are met on-site.

(Ord. 2024-18, § 1(Exh. A), 2024)