San Carlos, CA

Building an Accessory Dwelling Unit

ADU Picture Photo Credit: Neil Kelly;

Website updated March 11, 2024 

Recent ADU Ordinance Update: 
On Monday, November 13, 2023 the City Council adopted amendments to the Accessory Dwelling Unit (ADU) Ordinance (Ordinance 1604).  These amendments became effective on December 13, 2023, aiming to streamline the permitting process, ensure compliance with State laws, provide clarity for property owners and developers, and reduce barriers related to the development of ADUs and Junior Accessory Dwelling Units (JADUs). During this time, the City also adopted the associated Objective Design Standards for ADUs and JADUs which can be referenced within SCMC Section 18.04.040. 

The City is required to submit the amendments to the State Department of Housing and Community Development (HCD) within 60 days after adoption. The City has submitted these amendments to HCD and is waiting for HCD’s comments. If HCD finds that any portion of the Ordinance is not consistent with state law, the Ordinance can be sent back to the City for changes.  

On January 1, 2020, state ADU laws went into effect mandating updates to the City’s Accessory Dwelling Unit (ADU) ordinance. On October 26, 2020, the San Carlos City Council adopted its first ADU and JADU Ordinance. In the years since 2020, the state has passed several bills aimed at encouraging the construction of ADUs by reducing the regulatory barriers commonly found in local zoning ordinances. In response, the San Carlos ADU and JADU Ordinance was amended in November 2023 to comply with new State Laws, clarify existing text, and update policies.  
Should any conflict occur between the content provided herein on the City’s ADU/JADU webpage and the adopted ADU/JADU development standards codified under SCMC Section 18.23.210, which can be found, the development standards codified under SCMC Section 18.23.210 shall control. 

Frequently Asked Questions:  

What is an Accessory Dwelling Unit (ADU)? 
According to the California Government Code, an ADU is an attached or detached residential dwelling unit that provides complete independent living facilities for one (1) or more persons and located on a single lot with a proposed or existing single-unit dwelling. ADUs must include a separate external entrance and permanent provisions for living, sleeping, eating, cooking, and sanitation on the same parcel as the single-family or multifamily dwelling.  

What is a Junior Accessory Dwelling Unit (JADU)? 
A JADU is a unit that is no more than five hundred (500) square feet in size and contained entirely within a single-family dwelling unit. A JADU may include separate sanitation facilities or may share sanitation facilities with the single-family dwelling. An efficiency kitchen is required, which must include a sink and a built-in cooking facility with appliances. 

What is a Statewide Exemption Accessory Dwelling Unit (ADU)? 
A Statewide exemption ADU, found in Government Code Section 65852, subdivision (e), is an ADU of up to eight hundred (800) square feet, sixteen (16) feet in height (eighteen (18) feet near transit or when the primary dwelling has more than one (1) story, twenty-five (25) feet or the underlying zoning height limit, whichever is lower, for an attached ADU), as potentially limited by a local agency, and with four (4) foot side and rear yard setbacks. State ADU law requires that no lot coverage, floor area ratio, open space, front setback, or minimum lot size will preclude the construction of a Statewide exemption ADU.  

How and where do I apply for an ADU/JADU?
ADUs and JADUs are approved ministerially without discretionary review or a hearing.  
An ADU/JADU application can be submitted directly through the building department. For more information click HERE 

Please also refer to “Checklist for New Homes & Residential Additions” for more information on what is required in a Building Permit Plan set. 

What are the requirements for ADUs?
Quick Guide:
San Carlos ADU JADU Development Requirements 2024
If you are looking to apply for an Accessory Dwelling Unit or a Junior Accessory Dwelling Unit within the City of San Carlos, please refer to the SCMC Section 18.23.210 for specific regulations. 

In what areas of San Carlos are ADUs/JADUs permitted? 
Generally, ADUs are permitted in all zoning districts that allow residential uses, including single-family residential (RS) and multi-family residential (RM) zoning districts. JADUs are permitted in the RS zoning districts within an existing single-unit dwelling, or as part of a proposed new single-unit dwelling. 
How many ADUs/JADUs can I add to my property?
Generally, one ADU and one JADU are allowed per single-family residential lot. Accordingly, a single-family residential lot may contain a primary residence, one ADU, and one JADU. Multiple ADUs may be permitted on multi-family residential properties. Contact the Planning Division for more information on multi-family residential ADUs or refer to SCMC Section 18.23.210. 

Where can an ADU be located on my property?
An ADU may be:

  • Attached to an existing or proposed single-unit dwelling;
  • Located within the walls of the existing or proposed single-unit dwelling, including all or a portion of an attached garage;
  • Located within or added onto an existing accessory structure;
  • Located over or below a legally established detached garage;
  • Detached from the existing or proposed single-unit dwelling or multifamily structure, but located on the same lot as the existing or proposed single-unit dwelling or multifamily structure. 

Where can a JADU be located on my property?
A JADU can be located within the walls of an existing or proposed single-dwelling unit                                                                                                                          
Does the City of San Carlos Have Pre-Approved ADU plans? 
No, the City of San Carlos does not currently have pre-approved ADU plans. 

The City of San Carlos is working with
Symbium to develop pre-approved ADU plans and incorporate San Carlos’s ADU requirements into an interactive parcel map that allows residents to see how different ADU models will fit/look on their property.  
Pre-approved ADU plans and the Symbium interactive map will be available by January 2025. 
Updates will be posted on the San Carlos ADU / JADU webpage as the project develops.  

Are impact fees collected on ADUs/JADUs? 
No impact fees are collected on a JADU or ADU that is less than 750 square feet in size. “Impact fees” include the fees specified in Sections 66000 and 66477 of the California Government Code but does not include utility connection fees or capacity charges. For ADUs that have a floor area of 750 square feet or more, impact fees shall be charged proportionately in relation to the square footage of the single-unit dwelling. 
Can I sell my ADU/JADU? 
No, the City of San Carlos does not allow separate sale of ADUs and JADUs from the primary residence. 
Can I rent my ADU/JADU? 
Yes. ADUs and JADUs may be rented independently from the primary residence. 
However,  ADUs and JADUs may not be rented for fewer than 30 consecutive calendar days. 
Am I required to record a deed restriction? 
Deed restrictions are not required for ADUs. ADUs do not have owner occupancy requirements 
Recordation of a deed restriction is required for JADUs pursuant to the California Government Code. The required deed restriction prohibits (1) the sale of the JADU separate from the sale of the single-family residence and (2) a restriction on the size and attributes of the JADU. Deed restriction requests must be filed with the Planning Division in conjunction with your building permit request. Note that deed restrictions will be recorded with the County of San Mateo and may be enforced against future purchasers of the property. 

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Resources18 documents

City Documents13 documents

  • Second Reading of the updated ADU and JADU Ordinance- City Council Meeting October 26, 2020
    document date none
  • First Reading of the updated ADU and JADU Ordinance- City Council Meeting October 12, 2020
    document date none
  • ADU Ordinance Agenda Packet- City Council Meeting July 13, 2020 (POSTPONED)
    document date none
  • ADU Ordinance Agenda Packet- City Council Meeting Jun. 22, 2020 (POSTPONED)
    document date none
  • ADU Ordinance Agenda Packet- Planning Commission Meeting Jun. 1, 2020
    document date none
  • ADU Study Session Staff Report - Oct. 7, 2019
    document date none
  • ADU Study Session Presentation- Oct. 7, 2019
    document date none
  • T&C ADU Staff Report- Dec. 17, 2019
    document date none
  • T&C ADU Presentation-Dec. 17, 2019
    document date none
  • Exhibit A to Ordinance 1604- Amendments to ADU Code Redline
    document date 03-11-2024
  • Ordinance 1604- Adopted November 13, 2023
    document date 03-11-2024
  • Staff Report Ordinance 1604- November 13, 2023
    document date 03-11-2024
  • Planning and Transportation Commission Ordinance1604 Study Session- May 15, 2023
    document date 03-11-2024

External Resources5 documents

  • HCD ADU Handbook
    document date none
  • HCD ADU and JADU Info
    document date none
  • Second Unit Center
    document date none
  • 21 Elements ADU and JADU Info
    document date none
  • Home for All ADU Info
    document date none

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