San Carlos, CA

Building an Accessory Dwelling Unit

Photo by: New Avenue Homes
ADU and JADU Ordinance 

On January 1, 2020, state ADU laws went into effect mandating updates to the City’s Accessory Dwelling Unit (ADU) ordinance. These laws include AB 68, AB 587, AB 881, and SB 13. Key components contained in these laws cover the topics of streamlined ADU review, reduced fees, more flexible development standards, modification to parking requirements, provisions for Junior ADUs (JADUs), multi-family dwelling ADUs, owner occupancy requirements, short-term rental restrictions, garage conversions, nonconformities, and code enforcement. The laws aim to encourage the construction of ADUs by reducing the regulatory barriers commonly found in local zoning ordinances. On October 26, 2020, the San Carlos City Council adopted an ADU and JADU Ordinance, which went into effect on November 25, 2020. The list below provides reader-friendly guidelines for potential applicants.

Disclaimer: 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 18.23.210, which can be found here, the development standards codified under SCMC 18.23.210 shall control.

What is an Accessory Dwelling Unit (ADU)?

According to the California Government Code, an ADU is an attached or a detached residential dwelling unit that provides complete independent living facilities and is located on a lot with a proposed or existing primary residence. ADUs must include permanent provisions for living, sleeping, eating, cooking, and sanitation on the same parcel as the single-family or multi-family dwelling is located.

What is a Junior Accessory Dwelling Unit (JADU)?

A JADU is a residential dwelling unit that is no more than 500 square feet in size and is contained entirely within the walls of an existing or proposed single-family residence (including attached garages). A JADU may include separate sanitation facilities, or may share sanitation facilities with the existing structure.

In what areas of San Carlos are ADUs/JADUs permitted?
Generally, ADUs are permitted in all zoning districts that allow residential uses, including the 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 up to three dwelling units including the 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.

Where can an ADU be located on my property?

An ADU may be located in any of the following places:

  • Attached to a primary residence
  • Detached from a primary residence
  • Within the walls of a primary residence, including all or a portion of an attached garage
  • Within an existing detached accessory structure
  • Over a legally established detached garage
What are the requirements for ADUs?

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, ADUs and JADUs cannot be separately sold from the primary residence.

Can I rent my ADU/JADU?

Yes. ADUs and JADUs may be rented independently from the primary residence.

Can I use my ADU/JADU for short-term rentals?

No. 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.

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.

Are there owner-occupancy requirements?

Yes. For JADUs, either the primary residence or the JADU must be owner-occupied.

For ADUs permitted before January 1, 2025, there is no owner-occupancy requirement. For applications received on or after January 1, 2025, either the primary residence or the ADU must be occupied by the owner.

Can I build a basement under an ADU/JADU?

Yes. However, for detached ADUs, the floor area of the basement counts towards gross floor area. Note that other City permit requirements, such as building and grading permits, may apply.
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Resources14 documents

City Documents9 documents

  • Second Reading of the updated ADU and JADU Ordinance- City Council Meeting October 26, 2020
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  • First Reading of the updated ADU and JADU Ordinance- City Council Meeting October 12, 2020
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  • ADU Ordinance Agenda Packet- City Council Meeting July 13, 2020 (POSTPONED)
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  • ADU Ordinance Agenda Packet- City Council Meeting Jun. 22, 2020 (POSTPONED)
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  • ADU Ordinance Agenda Packet- Planning Commission Meeting Jun. 1, 2020
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  • ADU Study Session Staff Report - Oct. 7, 2019
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  • ADU Study Session Presentation- Oct. 7, 2019
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  • T&C ADU Staff Report- Dec. 17, 2019
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  • T&C ADU Presentation-Dec. 17, 2019
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External Resources5 documents

  • HCD ADU Handbook
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  • HCD ADU and JADU Info
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  • Second Unit Center
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  • 21 Elements ADU and JADU Info
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  • Home for All ADU Info
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