Accessory Dwelling Unit (ADU) Regulations in the RH High Density Residential District

Accessory Dwelling Units (ADUs) are a permitted use within the RH (High Density Residential) zoning district in the City of Concord, subject to compliance with the standards established in the Concord Development Code. ADUs are allowed in the RH district because it is a zoning district that permits multifamily principal dwelling residential uses, and all such residential districts allow for the development of ADUs [Section 18.200.180(C)(7)].

ADU Development Standards

Accessory Dwelling Units in the RH district must comply with specific development and design standards to ensure compatibility with existing neighborhoods while facilitating the creation of smaller, affordable housing units.

Size and Height Limitations

The living area of an Accessory Dwelling Unit must be at least 150 square feet. The maximum size of an Accessory Dwelling Unit in the RH district is the lesser of 50 percent of the floor area of the principal dwelling or the following limits:

Lot Net Area	Maximum Accessory Dwelling Unit Size
Less than 12,000 square feet	1,000 square feet (excluding up to 230 sq. ft. for attached garages/carports)
12,000 square feet or greater	1,200 square feet (excluding up to 460 sq. ft. for attached garages/carports)

Note: The size limitation will be waived if it restricts the Accessory Dwelling Unit to less than 800 square feet [Section 18.200.180(C)(8)].

Height and Setback Requirements

The height and setback requirements for Accessory Dwelling Units in the RH district are as follows:

Feature	Requirement
Interior Side/Rear Setback	Minimum of 4 feet [Section 18.200.180(C)(16)]
Detached ADU Height	Generally 16 feet; may be 18 feet for lots with existing/proposed multifamily dwellings [Section 18.200.180(C)(17)]
Attached ADU Height	Maximum of 25 feet or the height of the principal dwelling, whichever is lower [Section 18.200.180(C)(17)]

General Requirements

All Accessory Dwelling Units within the City of Concord, including the RH district, must adhere to the following:

Permitting: A building permit is required for the construction of any Accessory Dwelling Unit [Section 18.200.180(C)(1)].
Foundation: A permanent foundation system is required in accordance with the Uniform Building Code [Section 18.200.180(C)(2)].
Subdivision Prohibited: Accessory Dwelling Units may not be sold independently of the principal dwelling unit, though they may be leased separately [Section 18.200.180(C)(4)].
Rental Duration: Accessory Dwelling Units cannot be rented for a term of less than 30 days [Section 18.200.180(C)(5)].

Parking Requirements

Parking required for an Accessory Dwelling Unit is in addition to the required parking for the principal dwelling. Generally, one off-street parking space is required per Accessory Dwelling Unit or per bedroom, whichever is less. However, parking is not required in the following instances:

The Accessory Dwelling Unit is located within a one-half mile walking distance of public transit.
The Accessory Dwelling Unit is located within a designated architecturally and historically significant historic district.
The Accessory Dwelling Unit is part of the proposed or existing principal dwelling or a conversion of an accessory structure.
On-street parking permits are required but not offered to the occupant of the Accessory Dwelling Unit.
There is a car share vehicle site located within one block of the Accessory Dwelling Unit.

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