Statewide Update: New California ADU Bills AB68, SB13, AB881, AB670 have passed. These laws create more options for building an ADU in 2020. Use ADU Services to learn how they affect your property!

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San Carlos ADUs

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San Carlos ADU Guidelines Last Updated 03/27/20

PLANNING OFFICE The city planning office is not open to the public at this time, but is accepting ADU permit questions and applications.

The city government of San Carlos will approve ADUs under California's statewide mandated regulations.
The California Building Code (CBC) 2019 is adopted.
Relevant state bill updates for SB13, AB68, AB881, AB670 are shown in green below.


City Hint: The city permitted a total of 12 ADU project(s) in the past year of 2018, which makes it above average for ADU production compared to other cities statewide.


Number of ADUs allowed:

Under state law, each single-family home may now construct at least one Accessory Dwelling Unit (ADU). Owner occupied single-family properties may construct one Accessory Dwelling Unit (ADU) and one Junior Accessory Dwelling Unit. Multi-family properties, per every four existing residential units, may construct one Accessory Dwelling Unit (ADU), so long as the existing units were legally established.

As of January 1st, 2020

Types of ADUs allowed:

Detached ADU, Attached ADU, Junior ADU are allowed. Accessory Dwelling Units may be new construction or converted from existing space. Junior Accessory Dwelling Units must be converted from existing space.

Lot size:

ADU projects on single family or multi-family residential lots will not be subject to the minimum lot size of the underlying local zoning code or by special ordinance. ~ AB68 & AB881 Update

As of January 1st, 2020

ADU size:

Single-family and multi-family Properties will be allowed to create 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 Califronia Residential Code. ~ AB-68

As of January 1st, 2020


Setbacks for a detached new construction ADU shall be no more than 4 feet from the rear and side lot lines. No setbacks shall be required for ADUs and Junior ADUs converted from legally eastablished existing space. Attached new construction ADUs and conversions from existing space to be expanded must comply with the setbacks of the underlying zone. ~ AB-68

As of January 1st, 2020


Properties which convert an existing garage to an Accessory Dwelling Unit or Junior Accessort Dwelling Unit (JADU) will not be subject to replacement parking requirements. ~ AB-68

As of January 1st, 2020

Fire Safety:

Per state standards.

Shape, materials and style:

Architectural Compatibility. The architectural design, exterior materials and colors, roof pitch and style, type of windows, and trim details of the accessory dwelling unit shall be substantially the same as and visually compatible with the primary dwelling.
Development Standards. ADUs shall conform to the height, setbacks, lot coverage and other zoning requirements of the zoning district in which the site is located, the following development standards, other requirements of the Zoning Ordinance, and other applicable City codes. In addition to all other requirements of the zoning district, any detached accessory dwelling units shall be located a minimum of five feet from all side and rear lot lines. ADUs located above garages must conform to the setback requirement for second stories in their respective zoning districts.


The maximum height of an ADU is 15’ unless located over, a garage and then it is 28’

Design review:

Ministerial review process.

Number of Bedrooms:

Not specified by State Standards.


Owner-occupancy will not be required for new ADUs (conversion and new construction) built between 2020 and 2025. ~ Updated: State Law SB-13

As of January 1st, 2020

Utility connections:

Local health officer approval where a private sewage disposal system is being used, if required. (State requirements)

Permit Fees

SB13 Update: As of January 1st, 2020, local impact fees for ADUs will be reduced substantially statewide.

Allowed Zones:

*** Beginning in 2020, according to state law, all residential zoning districts, including single-family and multi-family, are allowed to build Accessory Dwelling Units. ***

As of January 1st, 2020

Existing Units

Amnesty Program: An Amnesty Program exists for preexisting units constructed prior to January 1, 2003. Please reference the Secondary Living Unit Amnesty Program handout from the Building Division:

Joint Planning and Building Division approval is required for approval through the Amnesty Program for SDUs created prior to January 1, 2003.

SB13 Update: Amnesty program to permit unpermitted units will be administered statewide, allowing non-health and safety code violations to be deferred.

Emergency Access:

Emergency Access. A SDU may be permitted only on lots with access from a roadway that meets the fire apparatus access road requirements of the California Fire Code Section 902.2.2.1.


Location. Second units may be established on any lot in any district where a primary single-unit dwelling has been
previously established or is proposed to be established in conjunction with construction of a second unit and there is no
other second dwelling unit within four hundred feet measured from nearest edge of the lot line of each respective or
proposed second dwelling unit. The Director may grant a waiver to the four-hundred-foot separation requirement if he
finds that there are no substantial parking, privacy, noise, health and safety or visual impacts to neighbors associated
with the location and siting of the detached second dwelling unit. The Director shall hold a public hearing before allowing
a waiver with notice to neighbors at least twenty days prior to the hearing and as provided for in Chapter 18.27,
Common Procedures.


Waivers: There are 3 types of Waivers that may be granted by the Director after holding a public hearing with a
notice to property owners at least 20 days prior to the hearing as required in Chapter 18.27, Common Procedures.
Waivers to standards may include: setbacks from the 5’ requirement (only for SDUs created prior to January 1, 2003)
(1) , window and door openings, or the proposed location is within 400 feet of an existing approved SDU.

Residential Building Code:

The California Building Code (CBC) 2019 is adopted.

San Carlos City Planning Offices

San Carlos Planning & Zoning

Public counter and telephone hours are 9:00 a.m. to 12:00 p.m. weekdays.

600 Elm Street San Carlos, CA 94070 San Carlos, CA 94070

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* based on local average price per sqft


* estimated by location


* 30 years / 5% interest rate / 20% down payment


Appreciation Estimate = (Base Value: $) / (Home's Living Space: sqft) * (ADU's Living Space: sqft)

Rental Estimate = (Rent Per Sqft: $5.63) * (ADU's Living Space: sqft)

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