Accessory Dwelling Unit Regulations for RS-12 Zoning Districts in Concord

Accessory Dwelling Units (ADUs) are permitted in the RS-12 (Single-Family Residential) zoning district in the City of Concord, subject to development standards including size limitations, setback requirements, and design consistency. Property owners must obtain a building permit and adhere to specific size and placement criteria, though some provisions, such as those related to lot coverage or floor area ratio, may be waived if they prohibit the construction of an exempt ADU of up to 800 square feet.

Eligibility and Use

In the City of Concord, the RS-12 zoning district is classified under the "R (Residential)" category [Section 18.30.010, Table 18.30.020, Section 18.200.180(C)(7)]. Accessory dwelling units are permitted in all districts that allow for single-family or multifamily principal dwelling residential uses, including the R (Residential) district, which encompasses the RS-12 designation [Section 18.200.180(C)(7)].

An accessory dwelling unit (ADU) or junior accessory dwelling unit (JADU) that conforms to the established standards shall not be considered to exceed the allowable density for the RS-12 lot [Section 18.200.180(C)(3)].

Development Standards for ADUs

Accessory dwelling units in the City of Concord must comply with the following development and design standards:

Standard	Requirement
Minimum Living Area	150 square feet
Maximum Size	Lesser of 50% of the principal dwelling floor area or 1,000 square feet (for lots <12,000 sf); 1,200 square feet (for lots ≥12,000 sf)
Interior Side/Rear Setback	Minimum of 4 feet [Section 18.200.180(C)(16)]
Front/Corner Side Setback	Must comply with principal dwelling requirements
Maximum Height (Attached)	25 feet (or principal dwelling height, whichever is lower)
Maximum Height (Detached)	16 feet (standard); 18 feet (if near transit); or up to 18 feet for multistory principal dwellings

Note: The maximum size limitation will be waived if it restricts an accessory dwelling unit to less than 800 square feet [Section 18.200.180(C)(8)].

Design and Exterior Consistency

For accessory dwelling units other than pre-approved designs, exterior features must be consistent with the principal dwelling [Section 18.200.180(C)(10)]. Applicants must utilize at least two of the following approaches:

Use of at least one matching exterior color from the principal dwelling’s palette.
Use of at least two matching exterior materials from the principal dwelling’s material palette.
A roof slope matching the dominant pitch or form of the principal dwelling.

Parking Requirements

Parking required for an accessory dwelling unit in an RS-12 district is in addition to the required off-street parking for the principal single-family dwelling [Section 18.200.180(C)(11)]. Generally, one off-street space is required per ADU or per bedroom, whichever is less [Section 18.200.180(C)(11)(a)]. However, parking is not required if the RS-12 property is within one-half mile walking distance of public transit, is located in a designated architecturally significant historic district, is part of a conversion of an existing structure, or if there is a car share vehicle site within one block [Section 18.200.180(C)(11)(b)].

Prohibitions

Subdivision: No subdivision of land or air rights is allowed that would result in the accessory dwelling unit existing on a separate lot from the principal dwelling [Section 18.200.180(C)(4)].
Short-Term Rentals: Accessory dwelling units or junior accessory dwelling units shall not be rented for a term of less than 30 days [Section 18.200.180(C)(5)].

Sections Cited