Marysville City Zoning Code
CHAPTER 18
90 SECOND RESIDENTIAL UNITS IN RESIDENTIAL ZONES
§ 18.90.010 Purpose.
It is the purpose of this chapter to increase the supply of affordable housing within the city and to increase the utilization of the city's housing resources by permitting second residential units in all residential zones, subject to the provisions of this chapter.
(Ord. 1372 § 5(A) (part), 2015)
§ 18.90.020 Definitions.
ADUs are separate, complete homes for at least one person that are located on the same property as another, primary home. That means that ADUs have a place to live and sleep, a kitchen, and in most cases, their own bathroom.
(a)
"Accessory dwelling unit"
shall be as defined by Government Code Section 65852.2, as it now exists or may hereafter be amended, and means an attached or a detached residential dwelling unit that provides complete independent living facilities for one or more persons. The unit shall be located on a permanent foundation or a permanent chassis if a manufactured home, have an independent exterior access (if located within a single-family dwelling unit), and shall include permanent provisions or infrastructure to support living, sleeping, eating, cooking, and sanitation on the same parcel as where a single-family, two-family or multi-family dwelling is situated or proposed to be situated. Accessory dwelling units can also include efficiency units, as defined in Health and Safety Code Section 17958.1, manufactured homes, as defined in Health and Safety Code Section 18007, second dwelling units, granny flats, in-law quarters, casitas, carriage units, and tiny houses as long as such units otherwise meet this definition.
(b)
"Accessory structure"
means a structure that is accessory and incidental to a single-family, two-family or multi-family dwelling located on the same lot.
(c)
"Car share vehicle"
means a vehicle that can be rented for short periods of time and is available 24 hours a day, seven days a week at unattended self-service locations.
(d)
"Existing structure,"
for the purposes of defining an allowable space that can be converted to an accessory dwelling unit, means the following:
(1)
The proposed accessory dwelling unit is located within the walls and roofline of a fully enclosed, existing structure (i.e., the existing footprint); and
(2)
The existing structure can be made safely habitable under local building codes at the determination of the building official, regardless of any nonconforming zoning conditions.
(e)
"Junior accessory dwelling unit"
shall be as defined by Government Code Section 65852.22, as it now exists or may hereafter be amended, and means a unit that is no more than 500 square feet in size and contained entirely within an existing or proposed single-family dwelling. A junior accessory dwelling unit may include separate sanitation facilities or may share sanitation facilities with the existing structure.
(f)
"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.
(g)
"Nonconforming zoning condition"
means a physical improvement on a property that does not conform with current zoning standards.
(h)
"Passageway"
means a pathway that is unobstructed clear to the sky and extends from a street to one entrance of the accessory dwelling unit.
(i)
"Permanent provisions or infrastructure,"
in the context of the definition of an "accessory dwelling unit," means a permanent kitchen consisting of a sink, a counter for food preparation, a food storage area, and either a minimum 220V receptacle or a dedicated gas line for a cooking appliance (a 110V receptacle for a microwave, toaster, hotplate, etc., is not a permanent provision); a toilet connected to plumbing; a bathroom sink connected to plumbing; and a bathing facility connected to plumbing, such as a shower or bathtub.
(j)
"Primary dwelling unit"
means a proposed or existing single-family, two-family or multi-family dwelling unit located on the lot where the accessory dwelling unit is proposed to be developed, and includes attached, enclosed accessory structures, such as a garage.
(k)
"Proposed dwelling"
means a dwelling that is the subject of a permit application and that meets the requirements for permitting.
(l)
"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.
(m)
"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.
(n)
"Within the existing space"
includes areas within an existing primary dwelling unit or within an existing attached or detached accessory structure such as a garage, storage area, a carriage house, a pool house, studio, and similar enclosed structures. The addition of square footage, including, but not limited to, the addition of another floor, is not considered to be "within the existing space," unless the expansion is for the purposes of ingress and egress and does not exceed 150 square feet. Additions of square footage which are not "within the existing space" are considered new construction.
(Ord. 1372 § 5(A) (part), 2015; Ord. 1463, 10/7/2025)
§ 18.90.030 Areas permitted.
A second residential unit is permitted on any lot or parcel in residential zones, subject to the provisions and restrictions of this chapter.
(Ord. 1372 § 5(A) (part), 2015)
§ 18.90.040 Permit requirements.
A building permit shall be required prior to construction or creation of an accessory dwelling unit or junior accessory dwelling unit. Any ADU outside of the historic district that satisfies the requirements of this chapter shall be ministerially approved.
(Ord. 1372 § 5(A) (part), 2015; Ord. 1463, 10/7/2025)
§ 18.90.050 Designated areas.
(a)
Mixed Use and Residential Zones. Accessory dwelling units are principally permitted in the commercial mixed use (CMU), single-family residential (R-1), small lot residential (RS), two-family residential (R-2), multi-family housing (R-3), and residential mixed use (RMU) zoning districts, provided the lot contains an existing or proposed single-family, two-family or multi-family dwelling unit as defined in Chapter 18.04 (Residential Use Types) and the accessory dwelling unit complies with the standards identified in this chapter.
(b)
Zones. Accessory dwelling units are also principally permitted in the commercial zoning districts, provided the lot contains an existing or proposed single-family, two-family or multi-family dwelling unit (Residential Use Types) and the accessory dwelling unit complies with the standards identified in this chapter. If a commercially zoned lot contains an existing single-family, two-family or multi-family dwelling unit which does not have an approved conditional use permit, then the accessory dwelling unit shall be required to obtain an Administrative Permit pursuant to Chapter 18 (Permit and Variance Requirements).
(Ord. 1463, 10/7/2025)
§ 18.90.060 Development standards for accessory dwelling units proposed within existing structures or existing living areas.
Accessory dwelling units are permitted to be developed within existing structures or within the living area of an existing primary dwelling unit. Accessory dwelling units developed within existing structures or living areas shall be allowed only in compliance with the following standards:
(a)
Setbacks. No setback shall be required for an accessory dwelling unit, including porches, decks, balconies, stairs, and patios which are attached to and for the use of the accessory dwelling unit, built within the footprint and dimensions of an existing living area or existing structure.
(b)
Floor Area. The total floor area of an attached accessory dwelling unit developed within an existing primary dwelling unit shall not exceed 50 percent of the floor area of the existing primary dwelling unit, except that an expansion of up to 150 square feet beyond the same physical dimensions as the existing primary dwelling unit is permitted for accommodating ingress and egress. The total floor area for a detached accessory dwelling unit developed within an existing detached accessory structure shall not exceed the floor area of the existing detached accessory structure, except that an expansion of up to 150 square feet beyond the same physical dimensions as the existing detached accessory structure is permitted for accommodating ingress and egress.
(c)
Unit Sizes.
(1)
An accessory dwelling unit shall not be less than the minimum size for an efficiency unit, as defined in Health and Safety Code Section 17958.1, as it now exists or may hereafter be amended.
(2)
An accessory dwelling unit shall not be more than 850 square feet for a studio or one-bedroom or more than 1,000 square feet for an accessory dwelling unit that provides more than one bedroom.
(d)
Minimum Facilities. Accessory dwelling units developed within existing structures or living areas shall include permanent provisions for independent living, sleeping, eating, cooking, and sanitation within the unit and must include a separate exterior entrance from the primary dwelling unit if the primary dwelling is a single-family dwelling.
(e)
Appearance. The accessory dwelling unit shall be designed and constructed so as to be compatible with the existing primary dwelling unit and neighborhood in terms of form, and materials, as determined by the Community Development Director or designee applying objective standards, and the accessory dwelling unit shall be subordinate to the primary dwelling unit. Manufactured homes shall meet the architectural standards set forth in Section 18.16.030 (Residential zone general development standards).
(f)
Historic District or Individual Historic Resources.
(1)
Design review within the historic district or individual historic resources shall be required, consistent with the Historic Design Guidelines.
(2)
Windows and doors original to structures on historic properties (including openings and garage doors) must be retained, unless this would prevent creation of the ADU.
(3)
Newly constructed ADUs and JADUs in landmark and historic districts should make every attempt to reduce visibility from the public right-of-way.
(g)
Parking Requirements. Accessory dwelling units developed within existing structures or living areas shall not be required to provide parking. A garage, carport, or covered parking structure shall be subject to the development regulations of the city, if the owner chooses to provide parking as part of the accessory dwelling unit. In addition, when a garage, carport, or covered parking structure is converted to an accessory dwelling unit, the required off-street parking spaces for the primary dwelling unit, if eliminated, do not need to be replaced. If the property owner chooses to replace the parking spaces, the replacement spaces may be located in any configuration on the same lot as the accessory dwelling unit, including within the front yard or street side setback, and may be covered spaces subject to conformance with the applicable requirements set forth in Chapter 18.16 (Permitted accessory structures to dwelling use type (single-family and two-family)).
(h)
Passageways. No passageways shall be required in conjunction with accessory dwelling units developed within existing structures or living areas.
(i)
Building and Fire Codes. Except as otherwise provided in this chapter, accessory dwelling units developed within existing structures or living areas shall comply with all local building and fire codes.
(j)
Fire Sprinklers. Accessory dwelling units developed within existing structures or living areas shall not be required to provide fire sprinklers if fire sprinklers were not required for the primary dwelling unit.
(k)
Utilities. Accessory dwelling units developed within existing structures or living areas shall not be required to install a new or separate utility connection directly between the accessory dwelling unit and the public utility infrastructure unless the accessory dwelling unit was constructed with a new single-family dwelling unit. However, if necessary, utility infrastructure does not exist with capacity available to serve both the primary dwelling unit and the accessory dwelling unit, the property owner shall be responsible for all costs related to installation of necessary infrastructure or upsizing existing infrastructure. Property owners may install a new or separate utility connection directly between the accessory dwelling unit and the public utility infrastructure at the property owner's option and expense.
(l)
Height. Detached ADUs: 16 feet on a lot with a proposed or existing single-family or multifamily dwelling unit (Cal. Gov't Code § 66321(b)(4)(A)). 18 feet on a lot with an existing or proposed single-family or multifamily dwelling, including an additional two feet to accommodate roof pitch that aligns with the primary dwelling, when the lot is a half-mile from a major transit stop or high-quality transit corridor (Cal. Gov't Code § 66321(b)(4)(B)). 18 feet height on a lot with an existing or proposed multifamily, multistory dwelling (Cal. Gov't Code § 66321(b)(4)(C)). If a detached two-story ADU can be built according to the height allowances required under State ADU Law while remaining compliant with the building code, a local agency cannot deny an ADU application to create a two-story ADU, irrespective of the underlying zoning that might restrict a primary dwelling to one story. (Cal. Gov't Code §§ 66321(b)(4)(D) and 66314(d)(8).) Attached ADUs 25 feet or the height limitation that applies to the primary dwelling in the local zoning ordinance, whichever is lower (Cal. Gov't Code §§ 66321(b)(4)(D)).
(m)
Number Permitted. A combination of up to two accessory dwelling/junior accessory dwelling units are permitted within areas zoned to allow single-family or two-family residential use provided the lot contains an existing or proposed single-family dwelling, and the accessory dwelling/junior accessory dwelling unit complies with the standards identified in this chapter (Accessory Dwelling Units). Up to two detached ADUs are allowed on a lot that has a proposed multifamily dwelling, or up to eight detached ADUs are allowed on a lot with an existing multifamily dwelling, not to exceed the number of existing units on the lot.
(n)
Exceptions to Development Standards.
(1)
One accessory dwelling unit and one junior accessory dwelling unit is permitted per lot with a proposed or existing single-family dwelling if all of the following apply:
(A)
The accessory dwelling unit or junior accessory dwelling unit is within the proposed space of a single-family dwelling unit or existing space of a single-family dwelling unit or accessory structure and may include an expansion of not more than 150 square feet beyond the same physical dimensions as the existing accessory structure. An expansion beyond the physical dimensions of the existing accessory structure shall be limited to accommodating ingress and egress.
(B)
The space has exterior access from the proposed or existing single-family dwelling unit.
(C)
The side and rear setbacks are sufficient for fire and safety.
(D)
The junior accessory dwelling unit complies with the requirements of Government Code Section 65852.22, as it now exists or may hereafter be amended.
(2)
Multiple accessory dwelling units within portions of existing multi-family dwelling units are permitted in areas not used as livable spaces, including, but not limited to, storage rooms, boiler rooms, passageways, attics, basements, or garages, if all of the following apply:
(A)
Each unit complies with state building codes for dwellings.
(B)
At least one accessory dwelling unit is permitted within an existing multi-family dwelling or up to eight ADU within the existing multi-family dwelling units may be converted to accessory dwelling units, whichever is greater.
(3)
Two detached accessory dwelling units are permitted per lot that have an existing multi-family dwelling unit, subject to a height limit of 16 feet and four-foot rear and side setbacks.
(o)
Waivers. Notwithstanding anything to the contrary contained in this title, limits on height, setbacks, lot coverage, floor area ratio, open space, and lot sizes are hereby waived if they do not permit at least an 800 square foot accessory dwelling unit that is at least 16 feet in height, and which provides four-foot rear and side setbacks.
(Ord. 1463, 10/7/2025)
§ 18.90.070 Development standards for accessory dwelling units proposed as new construction.
Newly constructed accessory dwelling units are permitted to be attached to a proposed or existing primary dwelling unit or detached from a proposed or existing primary dwelling unit as long as the newly constructed accessory dwelling unit is located on the same lot as a proposed or existing primary dwelling unit. Newly constructed accessory dwelling units shall be allowed only in compliance with the following standards:
(a)
Minimum Lot Area. There is no minimum lot area.
(b)
Maximum Lot Coverage. There is no maximum lot coverage.
(c)
Setbacks. No setback shall be required for an accessory dwelling unit constructed in the same location (i.e., footprint) and to the same dimensions as an existing accessory structure. A setback of four feet from the side and rear lot lines shall be required for an accessory dwelling unit that is otherwise newly constructed, including porches, decks, balconies, stairs, and patios which are attached to and for the use of the accessory dwelling unit.
(d)
Floor Area. The total floor area of an attached accessory dwelling unit shall not be less than 150 square feet nor exceed the standards of subsection (e) of this section (Unit sizes). The total floor area for a detached accessory dwelling unit shall not be less than 150 square feet nor exceed the standards of subsection (e) of this section (Unit sizes).
Development Standards Table | |||||
|---|---|---|---|---|---|
Size | Parking Required | Setbacks | Lot Coverage | Compatibility | |
Attached Junior | 500 sf | none | within the allowed footprint | N/A | N/A |
Attached ADU | Less than 50% of primary floor area | none | None if within same footprint of original structure | None | Match existing materials |
Detached ADU | Not less than 150 sf or more than 850 sf for a single bedroom or more than 1,000 sf with more than one bedroom | 1 may be in tandem | 4' side and rear, not in street side or front yard | None | Match existing materials |
(e)
Unit Sizes.
(1)
An accessory dwelling unit shall not be less than the minimum size for an efficiency unit, as defined in Health and Safety Code Section 17958.1, as it now exists or may hereafter be amended.
(2)
An accessory dwelling unit shall not be more than 850 square feet for a studio or one-bedroom or more than 1,000 square feet for an accessory dwelling unit that provides more than one bedroom.
(f)
Minimum Facilities. The accessory dwelling unit shall include permanent provisions for independent living, sleeping, eating, cooking, and sanitation within the unit and must include a separate exterior entrance from the primary dwelling unit if the primary dwelling is a single-family dwelling.
(g)
Appearance. The accessory dwelling unit shall be designed and constructed so as to be compatible with the proposed or existing primary dwelling unit and neighborhood in terms of height, form, and materials, as determined by the Community Development Director or designee applying objective standards, and the accessory dwelling unit shall be subordinate to the primary dwelling unit.
(h)
Parking Requirements. Garages, carports, and covered parking structures attached to the accessory dwelling unit and built to satisfy the required parking standards for the accessory dwelling unit are subject to the same setbacks and other development regulations as the accessory dwelling unit.
(1)
Accessory dwelling units with one or more bedrooms shall provide one off-street parking space. Studios shall not be required to provide any parking spaces. The parking requirement for accessory dwelling units with bedrooms can be met by providing the required parking space within the front yard setback and may be located in tandem with other on-site parking as long as it complies with the requirements.
(2)
When a garage, carport, or covered parking structure is demolished in conjunction with the construction of an accessory dwelling unit, the required off-street parking spaces for the primary dwelling unit, if eliminated, do not need to be replaced. If the property owner chooses to replace these parking spaces, the replacement spaces may be located in any configuration on the same lot as the accessory dwelling unit, including within the front yard or street side setback, and may be covered spaces subject to conformance with the applicable requirements set forth in this title.
(3)
Notwithstanding the above, accessory dwelling units shall not be required to provide parking in any of the following circumstances:
(A)
When the accessory dwelling unit is located within one-half mile walking distance of public transit.
(B)
When the accessory dwelling unit is located within the Downtown Historic District or Downtown Specific Plan.
(C)
When the accessory dwelling unit is part of an existing or proposed primary dwelling unit or an existing accessory structure.
(D)
When on-street parking permits are required but not offered to the occupant of the accessory dwelling unit.
(E)
When there is a car share vehicle located within one block of the accessory dwelling unit.
(i)
Passageways. No passageways shall be required in conjunction with the construction of an accessory dwelling unit.
(j)
Building and Fire Codes. Except as otherwise provided in this chapter, newly constructed accessory dwelling units shall comply with all local building and fire codes.
(k)
Fire Sprinklers. Accessory dwelling units shall not be required to provide fire sprinklers if fire sprinklers were not required for the primary dwelling unit.
(l)
Utilities. New or separate utility connections directly between the accessory dwelling unit and the public utility infrastructure shall only be required if directed by the utilities department. In such cases, if necessary, utility infrastructure does not exist with capacity available to serve both the primary dwelling unit and the accessory dwelling unit, the property owner shall be responsible for all costs related to installation of necessary infrastructure or upsizing existing infrastructure.
(m)
Height. An accessory dwelling unit shall not exceed the height limits prescribed in Residential zone general development standards for the zone in which the accessory dwelling unit will be located, or if not within a residential zone, the height shall not exceed the standards established for the single-family residential (R-1) zone.
(n)
Number Permitted. Except as otherwise permitted, only one accessory dwelling unit is permitted per lot.
(o)
Exceptions to Development Standards.
(1)
One newly constructed detached accessory dwelling unit that does not exceed four-foot rear and side setbacks, which may be combined with one junior accessory dwelling unit, is permitted per lot if all of the following apply:
(A)
The total floor area for the newly constructed detached accessory dwelling unit shall not exceed 800 square feet.
(B)
The newly constructed detached accessory dwelling unit shall not exceed 16 feet in height.
(2)
Two newly constructed detached accessory dwelling units are permitted per lot that has an existing multi-family dwelling unit, subject to a height limit of 16 feet and four-foot rear and side setbacks.
(p)
Waivers. Notwithstanding anything to the contrary contained in this title, limits on height, setbacks, lot coverage, floor area ratio, open space, and lot sizes are hereby waived if they do not permit at least an 800 square foot accessory dwelling unit that is at least 16 feet in height, and which provides four-foot rear and side setbacks.
(Ord. 1463, 10/7/2025)
§ 18.90.080 Use restrictions.
(a)
Sales Prohibited, Exceptions. Accessory dwelling units shall not be sold independently of the primary dwelling unit on the lot unless all of the criteria of Government Code Section 65852.26, as may be amended from time to time, are met, including that the accessory dwelling unit or the primary dwelling unit was built or developed by a qualified nonprofit corporation and there are affordability restrictions on the sale and conveyance of the accessory dwelling unit or primary residence that ensure the accessory dwelling unit and primary dwelling will be preserved for low income housing for 45 years for owner-occupied housing units and will be sold or resold to a qualified buyer.
(b)
Rentals. Accessory dwelling units may be rented as long as the rental term exceeds 30 calendar days.
(Ord. 1463, 10/7/2025)
§ 18.90.090 Nonconforming zoning conditions.
An accessory dwelling unit or junior accessory dwelling unit in compliance with the standards set forth in this chapter is still permitted even when the primary dwelling unit has a nonconforming zoning condition.
(Ord. 1463, 10/7/2025)
§ 18.90.100 Junior accessory dwelling units.
(a)
Junior accessory dwelling units are principally permitted within areas zoned to allow single-family residential use and must be located on a lot that contains an existing or proposed single-family dwelling unit as defined in Chapter 18.04 (Residential use types).
(b)
Junior accessory dwelling units are subject to the following conditions:
(1)
Only one junior accessory dwelling unit is permitted per residential lot.
(2)
A junior accessory dwelling unit shall not exceed 500 square feet.
(3)
The junior accessory dwelling unit shall be constructed within the walls of the proposed or existing single-family dwelling unit, including attached garages.
(4)
The junior accessory dwelling shall include a separate entrance from the main entrance to the proposed or existing single-family dwelling unit.
(5)
The permitted junior accessory dwelling unit must include an efficiency kitchen, which shall include at a minimum all of the following:
(A)
A cooking facility with appliances.
(B)
A food preparation counter and storage cabinets that are of reasonable size in relation to the size of the junior accessory dwelling unit.
(6)
Junior accessory dwelling units shall comply with all local building and fire codes applicable to the existing single-family dwelling unit except that fire sprinklers shall not be required if fire sprinklers were not required for the single-family dwelling unit.
(7)
Junior accessory dwelling units may be rented as long as the rental term exceeds 30 calendar days.
(8)
Junior accessory dwelling units shall not be required to provide parking nor be required to provide replacement parking if constructed within an attached garage.
(9)
Junior accessory dwelling units shall comply with all other applicable requirements set forth in this chapter.
(Ord. 1463, 10/7/2025)
