Guesthouse and Accessory Dwelling Unit Regulations in Concord
In the Concord Development Code, guesthouses are primarily regulated under the classification of "Accessory Dwelling Units" (ADUs). These units are permitted on lots with a single-family or multifamily principal dwelling in designated zoning districts, provided they meet specific size, height, and design requirements to ensure neighborhood compatibility.
Definition and Permitted Districts
An Accessory Dwelling Unit (ADU) is defined as an attached, interior, or detached dwelling unit that provides complete independent living facilities for one or more persons, including permanent provisions for living, sleeping, eating, cooking, and sanitation [Section 18.20.030].
Accessory Dwelling Units are allowed in the following zoning districts that permit single-family or multifamily principal residential uses:
- R (Residential)
- NTS (North Todos Santos)
- CO (Community Office)
- CMX (Commercial Mixed-Use)
- NC (Neighborhood Commercial)
- DP (Downtown Pedestrian)
- DMX (Downtown Mixed-Use) [Section 18.200.180(C)(7)]
Development Standards for Accessory Dwelling Units
Accessory Dwelling Units must comply with the zoning development standards of the district in which they are located, except where such standards conflict with the specific requirements in Section 18.200.180 [Section 18.200.180(C)(9)].
Size and Height Limitations
The size of an Accessory Dwelling Unit is subject to the following limitations:
| Standard | Requirement |
|---|---|
| Minimum Living Area | 150 square feet |
| Maximum Size (General) | Lesser of 50% of the principal dwelling floor area or 1,000 sq. ft. (lots < 12,000 sq. ft.) |
| Maximum Size (General) | Lesser of 50% of the principal dwelling floor area or 1,200 sq. ft. (lots ≥ 12,000 sq. ft.) |
| Exemption | Size limitations waived if they restrict the ADU to less than 800 square feet |
Note: The maximum size for attached garages or carports excluded from these calculations is 230 sq. ft. for smaller lots and 460 sq. ft. for larger lots [Section 18.200.180(C)(8)].
Height Standards
| Type of Unit | Maximum Height |
|---|---|
| Attached ADU | 25 feet (or the height limit of the principal dwelling, whichever is lower) |
| Detached ADU (Standard) | 16 feet |
| Detached ADU (Near Transit) | 18 feet (if within 0.5 miles of a major transit stop) |
| Detached ADU (Multifamily site) | 18 feet |
Note: The planning division may allow additional height for single-story detached units if necessary for architectural compatibility [Section 18.200.180(C)(17)].
Parking Requirements
Parking for an Accessory Dwelling Unit is required in addition to the parking required for the principal dwelling, at a rate of one off-street space per unit or per bedroom, whichever is less [Section 18.200.180(C)(11)].
Parking Exemptions
Parking for an Accessory Dwelling Unit is not required if the unit meets any of the following criteria:
- Located within one-half mile walking distance of public transit.
- Located within a designated architecturally and historically significant historic district.
- Part of the proposed or existing principal dwelling or a conversion of an existing accessory structure.
- When on-street parking permits are required but not offered to the occupant.
- When a car share vehicle site is located within one block of the unit. [Section 18.200.180(C)(11)(b)]
General Design and Operational Requirements
- Permanent Foundation: All Accessory Dwelling Units require a permanent foundation in accordance with the Uniform Building Code [Section 18.200.180(C)(2)].
- Subdivision: Accessory Dwelling Units may not be sold independently of the principal dwelling [Section 18.200.180(C)(4)].
- Rentals: Short-term rentals (less than 30 days) are prohibited [Section 18.200.180(C)(5)].
- Design Consistency: Colors and materials for a new Accessory Dwelling Unit must be consistent with the principal dwelling [Section 18.200.180(C)(10)].
Sections Cited
- Section 18.20.030
- Section 18.200.180
- Section 18.160.100