Accessory Dwelling Unit (ADU) Permissions and Standards in Grass Valley
In the City of Grass Valley, Accessory Dwelling Units (ADUs)—also known as second units or carriage houses—are permitted in all residential zoning districts and several commercial and community development zones. The Grass Valley Development Code generally allows for one ADU per lot containing an existing or proposed primary residence, and the City must ministerially approve applications that meet established state and local building standards [Section 17.44.190].
Allowed Zoning Districts
The City of Grass Valley permits the establishment of Accessory Dwelling Units (ADUs) or carriage houses in the following zoning districts as a permitted ("P") use, subject to compliance with specific development standards:
Residential Zones
ADUs are permitted in all primary residential districts within the City of Grass Valley [Section 17.22.030, Table 2-7]:
- RE (Residential Estate)
- R-1 (Single-Family Residential)
- R-2 (Two-Family Residential)
- R-2A (Medium Density Residential)
- R-3 (Multiple Dwelling Residential)
Traditional Community Development Zones
ADUs are permitted in the following specialized community zones [Sections 17.21.050 - 17.21.080]:
- NC (Neighborhood Center)
- NC-Flex (Neighborhood Center Flex)
- NG-3 (Neighborhood General 3 - Transitional)
- NG-2 (Neighborhood General 2 - Traditional)
Commercial and Industrial Zones
In Grass Valley commercial and industrial districts, ADUs are permitted if there is an existing legally non-conforming single-family dwelling on the property [Section 17.24.030, Table 2-10, Footnote 2]:
- C-1 (Community Business District)
- C-2 (Central Business District)
- C-3 (Heavy Commercial)
- OP (Office Professional)
- CBP (Corporate Business Park)
- M-1 (Light Industrial)
- M-2 (General Industrial)
Development and Design Standards
Accessory Dwelling Units in the City of Grass Valley must comply with specific size, height, and setback requirements to ensure compatibility with the primary residence and the surrounding neighborhood.
| Feature | Standard Requirement |
|---|---|
| Maximum Number | One ADU per lot [Section 17.44.190.C.1] |
| Efficiency Unit Size | Minimum 150 square feet [Section 17.44.190.C.3.a] |
| One-Bedroom ADU Size | Maximum 850 square feet [Section 17.44.190.C.3.b] |
| Two+ Bedroom ADU Size | Maximum 1,000 square feet [Section 17.44.190.C.3.b] |
| Absolute Maximum Size | Shall not exceed 1,200 square feet or 50% of the primary dwelling floor area, whichever is less [Section 17.44.190.C.3.d] |
| Detached ADU Height | Maximum 16 feet [Section 17.44.190.C.3.c] |
| Side and Rear Setbacks | Minimum 4 feet [Section 17.44.190.C.3.c] |
| Building Separation | Minimum 10 feet from the primary dwelling [Section 17.44.190.C.8] |
Junior Accessory Dwelling Units (JADUs)
Grass Valley also recognizes Junior ADUs, which are units no more than 500 square feet in size contained entirely within a single-family residence. These units may include separate sanitation facilities or share them with the existing structure [Section 17.100.020].
Parking Requirements
The City of Grass Valley mandates off-street parking for ADUs based on the number of bedrooms, though certain exemptions apply based on proximity to public transit or location within a historic district.
| Unit Type | Required Off-Street Parking |
|---|---|
| Studio or One-Bedroom | 1 accessible space (in addition to spaces for the primary dwelling) |
| More than One-Bedroom | 2 spaces |
| Location/Method | May be located in front or side yard setbacks; tandem parking is allowed |
Parking Exemptions: No additional parking is required for a Grass Valley ADU if it is located within one-half mile of public transit, located within the City's Historical District, or is part of an existing primary residence or accessory structure [Section 17.44.190.C.6].
Use and Sale Restrictions
- Rental: ADUs may be rented but cannot be used for short-term rentals (stays of less than 30 days) [Section 17.44.190.E].
- Separate Sale: The City of Grass Valley prohibits the separate sale or financing of an ADU through a condominium plan or subdivision, except when developed by a qualified nonprofit corporation for low-income housing [Section 17.44.190.F].
- Impact Fees: Grass Valley does not impose impact fees on ADUs smaller than 750 square feet. For units 750 square feet or larger, fees are charged proportionately to the square footage of the primary dwelling [Section 17.44.190.G].
Sections Cited
- Section 17.21.050 - Neighborhood center (NC) standards
- Section 17.21.060 - Neighborhood center flex (NC-Flex) standards
- Section 17.21.070 - Neighborhood general 3 (NG-3) standards
- Section 17.21.080 - Neighborhood general 2 (NG-2) standards
- Section 17.22.030 - Residential zone allowable land uses and permit requirements
- Section 17.24.030 - Commercial and industrial zone land uses and permit requirements
- Section 17.44.190 - Accessory dwelling units (ADU)
- Section 17.100.020 - Definitions of specialized terms and phrases