Accessory Dwelling Unit (ADU) Regulations in the RR-20 Rural Residential District
In the Concord Rural Residential (RR-20) district, accessory dwelling units (ADUs) and junior accessory dwelling units (JADUs) are permitted as a way to increase the supply of smaller and affordable housing. Property owners in the RR-20 district must comply with specific size, height, and setback requirements, and must obtain a building permit for the construction of these units.
Accessory Dwelling Unit (ADU) Permissions in RR-20
The Concord Development Code classifies accessory dwelling units as residential uses that are permitted in zoning districts that allow single-family or multifamily principal dwelling residential uses [Section 18.200.180(C)(7)]. The RR-20 district is a residential zoning district and thus allows for the development of accessory dwelling units [Section 18.30.010].
An accessory dwelling unit in the RR-20 district is defined as an attached interior or detached dwelling unit that provides complete independent living facilities for one or more persons and is located on the same lot as a proposed or existing single-family principal dwelling [Section 18.200.180(B)].
Development Standards for Accessory Dwelling Units
Accessory dwelling units in the RR-20 district must adhere to the following development standards:
| Standard | Requirement |
|---|---|
| Minimum Size | 150 square feet [Section 18.200.180(C)(8)] |
| Maximum Size | Lesser of 50% of the principal dwelling floor area or 1,000 square feet (on lots less than 12,000 sq. ft.) [Section 18.200.180(C)(8)] |
| Interior Side/Rear Setback | Minimum of 4 feet [Section 18.200.180(C)(16)] |
| Attached Height Limit | Maximum of 25 feet or the height of the principal dwelling, whichever is lower [Section 18.200.180(C)(17)] |
| Detached Height Limit | Maximum of 16 feet (with specific exceptions for roof pitch/design up to 18 feet near transit) [Section 18.200.180(C)(17)] |
Key Requirements and Limitations
- Building Permit: A building permit is required for any accessory dwelling unit or junior accessory dwelling unit [Section 18.200.180(C)(1)].
- Subdivision Prohibited: 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: Renting an accessory dwelling unit for a term of less than 30 days is prohibited [Section 18.200.180(C)(5)].
- Parking: One off-street parking space is generally required per accessory dwelling unit or per bedroom, whichever is less, unless the unit qualifies for a parking exemption (e.g., location within one-half mile walking distance of public transit) [Section 18.200.180(C)(11)].
- Owner Occupancy: For building permit applications received after December 31, 2024, at least one owner of the lot must reside in either the principal dwelling or the accessory dwelling unit as their bona fide principal residence [Section 18.200.180(C)(15)].
Sections Cited
- Section 18.30.010 (Purpose)
- Section 18.200.180 (Accessory dwelling units)