Check your property's zoning, browse designs & get contractor estimates for your ADU project:
Last Updated 08/14/21
City Hint: The City of Redwood City permitted a total of 34 ADU projects in the past year of 2020.
Number of ADUs allowed:
Under state law, each single-family home may now build at least one Accessory Dwelling Unit (ADU). Owner occupied single-family lots may build one Accessory Dwelling Unit (ADU) and one JADU. Multi-family lots, per every four existing residential units, may build one Accessory Dwelling Unit (ADU), so long as the existing units were legally established.
Types of ADUs allowed:
Detached ADU, Attached ADU, Junior ADU are permitted. ADUs may be new construction or converted from existing space. JADUs must be converted from existing space.
Residential parcels will not be subject to any minimum lot size for ADUs by ordinance or of the underlying zoning district. ~ Updated: State Law AB-68
Single-family and multi-family Properties will be allowed to add up to 850 square ft. for a one bed ADU or up to 1,000 square ft. for a two bed ADU, regardless of the underlying zoning standards of the property. A Junior ADU up to 500 square ft. is allowed. The minimum size of any living unit (including ADUs and Junior ADUs) is 150 square ft. according to California Residential Code. ~ Updated: State Law AB-68
The maximum required setback for a detached new construction Accessory Dwelling Unit (ADU) shall be no more than 4 ft from the rear and side property lines. Setbacks will not be required for Accessory Dwelling Unit (ADU)s and Junior Accessory Dwelling Units converted from existing space that was legally eastablished. Attached Accessory Dwelling Unit (ADU)s and conversions from existing space to be expanded will be required to comply with the setbacks of the underlying zone. ~ AB-68
Parcels which convert an existing garage to an Accessory Dwelling Unit (ADU) or JADU will not be subject to replacement parking requirements. ~ AB-68
Fire sprinklers shall be installed for the ADU.
Shape, materials and style:
An accessory dwelling unit shall be architecturally compatible with the architectural style and exterior paint and materials of the single family dwelling on the same lot.
Maximum building height is 28 feet and structures shall not exceed 2.5 stories. The building height of a detached accessory dwelling unit shall not exceed the building height of a single-family dwelling on the same lot.
Ministerial review process.
Number of Bedrooms:
Up to one (1) bedroom shall be permitted.
Owner-occupancy will not be required for new Accessory Dwelling Unit (ADU)s (conversion and new construction) built between 2020 and 2025. ~ SB13 Update
shall be exempt from the requirement of upgrading a water main.
An accessory dwelling unit, commonly known as a second unit or in-law unit, is an attached or detached dwelling unit that is located on the same lot as a single family dwelling and provides complete living, sleeping, eating, cooking, and sanitation facilities
separate and independent of the main dwelling.
For lots that are greater than or equal to 10,000 square feet in the Residential Hillside (RH) or Residential Single-Family (R-1) Zoning Districts, the maximum allowable floor area for an ADU shall be 800 square feet and no more than two (2) bedrooms.
The homeowner may live offsite and rent out both the main house and the ADU due to:
a. A medical condition that requires residency elsewhere; or
b. The homeowner accepts a job transfer outside of the San Francisco Bay Area.
A detached ADU may be built within a required rear yard setback area provided that the ADU meets the following requirements:
a. Minimum Rear Yard Setback: 10 feet
b. Maximum Building Height: 14 feet
c. Maximum Wall Height: 9 feet
d. No more than 50% of the required rear yard setback area shall be covered by structures.
*** Beginning in 2020, according to state law, all residential zoning districts, including single-family and multi-family, are allowed to build Accessory Dwelling Units. ***
An Accessory Dwelling Unit (ADU) may be built on the same property as an existing or proposed single-family residence in the RH, R-1, R-2, R-3, R-4, and R-5 zoning districts.
The front yard shall be subject to the minimum pervious area and stormwater requirements of the underlying zoning district.
Total lot coverage is limited to 40 percent of the lot area. Not more than 40 50 percent of the required rear yard shall be covered by any combination of accessory buildings or an accessory dwelling unit subject.
Residential Building Code:
The California Building Code (CBC) 2019 is adopted.
Redwood City Planning Division
Contact Planner Diana O'Dell. Counter Hours: 8AM-5PM (M/W/F), and 12:30PM-5PM (T/Th) (walk-ins welcome)
1017 Middlefield Road Redwood City, CA 94063
ADU Design Library
Browse hundreds of models to find the right fit for your property.
ADU Model 156 sqft
13 ft x 12 ft
ADU Model 1120 sqft
35 ft x 32 ft
ADU Model 540 sqft
30 ft x 18 ft
This estimate is based on recently completed projects in the area and is inclusive of all typical soft costs such as permitting, design and engineering fees.