Secondary Units (also known as Accessory Dwelling Units or ADUs) add affordable housing opportunities throughout the City without significantly changing the aesthetic character of the surrounding neighborhood. These units are great life-cycle housing, supporting families through various stages of life. They provide safe, independent (or semi-independent), and inexpensive housing for the elderly or disabled, and provide housing for returning adult children. Secondary units also provide extra income to families to help with the increasing costs of homeownership in the Silicon Valley.
The current Secondary Unit zoning standards are found in Section 20.30.150 of the Zoning Ordinance. You may also refer to the Secondary Unit Review Worksheet to help determine eligibility for a Secondary Unit.
A Building Permit is required to build a Secondary Unit. Your project will be reviewed for conformance with the Zoning Ordinance and California Building Code. Please see the following Building and Fire Department directives specific to secondary units:
Building Separation Requirements for Attached Secondary Units
Fire Department Review Requirements for Secondary Units
Fees for construction of a secondary unit vary based on the project scope and location. Please see the Building Division Fee page for more information.
2018 Secondary Unit Ordinance Update
Based on community input, staff is presently evaluating updates to Section 20.30 of Title 20 (Zoning Code). Specifically, these updates could modify the lot size, setbacks, height, and parking exemptions for Secondary Units. Additionally, this update will provide clarifying definitions which will simplify the overall planning process for ADUs. Other related revisions to the Zoning Code could including modified paving and parking requirements. The first community meeting related to this Ordinance update was held at City Hall on February 12, 2018. Community outreach thus far indicates that there is significant interest in the areas identified in the below chart. There is also community interest related to parking and neighborhood densification with the introduction of more ADUs in existing neighborhoods.
We want to continue to hear from residents and stakeholders so that we can ensure that the revised ordinance addresses key items important to you. There will be three community meetings in March 2018, where you will have the opportunity to discuss and comment on potential updates to the Secondary Units Ordinance in the Zoning Code. The three meeting dates are listed below.
A. Thursday, March 22, 2018 from 5.30 p.m. - 6.30 p.m. at the Almaden Community Center
B. Monday, March 26, 2018 from 6.30 p.m. - 7.30 p.m. at the Alum Rock Community Library
C. Thursday, March 29, 2018 from 7.00 p.m. - 8.00 p.m. at the Willow Glen Community Center
Staff identified the below key areas, and which may be considered for this code update:
Considerations for Future Updates
Allowed in R-1, R-2, and PD (subject to R-1 standards) zoning districts, comprising of single-family residences.
Allow in R-M zoning district, (and on PD lots subject to R-1 standards and lot size), which comprise of single-family residences.
Minimum Lot Size (in sq ft)
5,445 sq.ft. – for both attached and detached units
Allow on lots with areas between 3,000 sq.ft. and 5,445 sq.ft. with restrictions on unit size. Not allowed on lots <3,000 sq.ft.
Minimum Setbacks from Property Line
0 (conversion), 5 feet
0 feet for existing structures (in compliance with Building and Fire Code); Allow 5 feet minimum from the side and rear property line for new units and for units constructed above a garage.
Single Story – 18 feet maximum, 14 feet mid- roof
Allow up to 22 feet maximum (measured from grade to top of roof) for a detached unit atop an existing garage/accessory structure.
Rear Yard Coverage
Not to exceed 40% for detached Secondary Unit, Accessory Building and Structures (except for pools)
No change proposed.
Detached Secondary Unit - Location
In rear yard, and at least 6 feet away from primary dwelling. Can be attached only to a detached garage.
Allow Secondary Units to be attached to and converted from other existing accessory buildings in addition to garages.
Maximum Unit square footage based on lot size
600 sq.ft. (5,445 - 9,000 sq.ft.); 650 sq,ft, (9,001 - 10,000);
800 sq,ft, (10,001+)
Limit to 500 sq.ft. (3,000 – 5,445 sq.ft,)
650 sq.ft, (5,445 - 9,000 sq.ft,);
700 sq.ft, (9,001 - 10,000 sq.ft,);
900 sq.ft, (10,001+ sq.ft,)
Number of Bedrooms
One bedroom or combined living and sleeping area
One bedroom with common living spaceor combined living and sleeping area
Attached dwelling unit shall NOT exceed 50% of the existing living area of the primary dwelling
Attached dwelling units shall not exceed 50% of the existing or proposed living area of the primary dwelling.
Parking Requirements and Driveway Width
Parking configurations in conformance with State Law
Allow parking within front and side setbacks for a garage conversions into a secondary unit.
Match appearance, and match roof form and pitch
Require visual compatibility with existing primary dwelling.
Junior Accessory Dwelling Unit
Allow maximum 500 square feet limited to up to 50% of the primary dwelling unit
Front Yard Paving
No more than 50% of the front setback shall be paved with asphalt, cement or any other impervious surfaces.
Allow no more than 50% of the front setback to be paved with asphalt, cement or any other impervious or pervioussurfaces.
Reduction in required off-street parking spaces
B(1)(a) No more than one dwelling occupies the lot.
Allow no more than one dwelling, in conjunction with a Secondary Unit, to occupy the lot.
Secondary Unit addition to a single-family lot located on the Historic Resources Inventory
Requires Single-Family House Permit
Waive requirements for a Single-Family House Permit for new detached Secondary Unit or for conversion of existing accessory structure with no exterior alterations.
Add definitions for conversion, Single-Family dwelling unit; area calculation for Secondary Units.