What is an ADU? | How to Apply for an ADU | Resources | Contact

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What is an Accessory Dwelling Unit?

An Accessory Dwelling Unit (ADU) is a smaller living unit on a property with its own kitchen and bathroom facilities.  Common names for an ADU include in-law unit, secondary unit, and backyard cottage. New ADUs are not allowed to be used exclusively as a short-term rental unit.

 ADU Ordinance  |  ADU Handout

How to Apply for an ADU

To apply for a permit to construct an ADU, fill out the ADU Completeness Checklist and submit for a Building Permit using the City's eTrakIt online permitting website. Submit completed construction plans, building permit application, and ADU checklist online: https://permits.redwoodcity.org/etrakit/  

For new detached ADUs, please note that a fire flow test is required as part of the permit submittal process to determine water availability to the site and to assist fire sprinkler system design, if necessary. Visit the City's Fire Flow webpage to schedule a test with Engineering Department. Typical lead time is four weeks.

Below are fee estimates for new ADUs.

*Fees above are an estimate and additional fees will be applied based on construction valuation and are evaluated on a case-by-case basis. Other fees include administrative fees,  maintenance fees, and miscellaneous fees. For all fees, please reference the City's Master Fee Schedule. 

San Mateo County ADU Resource Center

Unsure how to get started? Visit the San Mateo County ADU Resource Center at smcadu.org for a step-by-step guide to start the design process, apply for permits, guidance through the construction process, and tips for moving-in. The SMC ADU Resource Center is a joint effort between participating San Mateo County cities (including Redwood City) and the Community Planning Collaborative that provides information and tools to make it easier for homeowners to build second units and create new homes in the County.

The SMC ADU Center developed a workbook and website to help residents with the process of constructing an ADU:  ADU Guidebook

Pre-Reviewed ADU Plans 

What is a pre-reviewed plan? The City of Redwood City is launching a local pre-approved plan program, required under State Bill AB1332 as of January 1, 2025. A pre-review ADU plan will be reviewed for building code by a local, state, or federal government, and would reduce city permitting review timelines to 30 days.  

Coming soon, Redwood City will connect to The ADU Plans Gallery, which allows homeowners to browse and filter ADU designs and connect directly with designers and companies to use or purchase plans. Galleries include site-built plans built from scratch and prefabricated plans, which are fully or partially built off-site and delivered to your property.

All plans – even pre-approved ones – still require customized site planning and permitting based on your property. The pre-review designs will include structural, roof, and floor plans. Homeowners will have to coordinate with designers to include details like where the ADU sits on your lot, foundation plans, utility plans, and more, prior to submitting plans to the City for the expedited review.

For Designers: Contact planning@redwoodcity.org to submit plans for the ADU pre-review program.

For Homeowners: Please visit again soon for updates to the ADU Plans Gallery. 

HEART Free ADU Plans

The City is partnering with HEART (Housing Endowment and Regional Trust) of San Mateo County to provide free pre-reviewed plans to our residents with latest HEART’s latest initiative: GLADUR a Green and Livable Accessory Dwelling Unit Resource. 

Free Construction Plans - Funded by a Grant from the Bay Area Air Quality Management District, HEART has developed designs and construction plans for green, all-electric, detached ADUs that can be downloaded by the public at no cost.  In addition to the free designs, HEART provides a  comprehensive GLADUR ADU handbook highlighting environmentally friendly options and links to existing ADU resources.

Required User Agreement - All visitors are required to complete a User Agreement prior to using the GLADUR Construction Documents. Please visit the GLADUR ADU Center website to review the full construction plans, including the contemporary and traditional styles of the following four ADU types: 

• Studio (400 sq. ft.)
• One Bedroom (575 sq. ft.)
• One Bedroom (745 sq. ft.)
• Two Bedrooms (800 sq. ft.)

(Shown: Contemporary Two Bedroom Option)

Standard Requirements - The City has pre-reviewed the construction plans, allowing quicker approvals to homeowners. Applicants are still subject to zoning requirements, site-specific conditions review, and school district fees. Some examples of site specific or city requirements are:

• The foundation design (i.e. hillside or bay mud areas);
• Designated WUI (Wildland Urban Interface) areas;
• Fire Flow test to show sufficient water supply is required for each application;
• A School District notification. (Note: The city is required to have ADU recorded with the school district. The school district may have the right to collect school impact fees. This decision is independent from the City);
• Any project over $50,000 valuation is required to complete a Construction and Demolition recycling form;
• CAL Green checklist and standard BMP plan; and
• Size and location of utilities. 

For more information please visit the GLADUR ADU website.

ADU Requirements

Below are some key ADU requirements: 

• Junior accessory dwelling units (JADUs) are units of up to 500 square feet of converted space contained entirely within a single-family home. A JADU may share a bathroom with the existing home.
• ADUs are allowed in multifamily units. Conversion of uninhabited spaces, including garages, will be allowed for at least one ADU or up to 25% of units in multifamily buildings. Plus, up to two detached ADUs with 4-foot setbacks will also be allowed.
• Up to 850 square feet for a one-bedroom ADU, or 1,000 square feet for an ADU with more than one bedroom.
• New detached ADUs shall be set back a minimum of 4 ft. from side and rear property lines.

• No impact fees are charged on ADUs less than 750 square feet. 
• Short-term rentals of new ADUs or JADUs are not permitted. 
• For more information, please view the Zoning Ordinance, Article 37 - Accessory Dwelling Units

For more information and to review the City's ADU Ordinance, go here. 

ADU Homeowner Survey

Beginning May 1, 2025, the City requires homeowners to complete a brief survey about their ADU in order to finalize their ADU Building Permit.

The purpose of this survey is to respond to state requests for data about ADU rents and to help the City of Redwood City understand how ADUs are being used. If you do not know the answer to a specific question (like how much rent you plan to charge), please provide your best estimate. Please note that the survey asks for your email address, however you may choose to not provide your email. Your data will remain anonymous.

After completing the survey, you will receive an email confirmation as proof of completion and should submit it to the Building Department at permits@redwoodcity.org. Feel free to contact staff at planning@redwoodcity.org for questions regarding the survey.

Please follow the link to complete your survey today: ADU Homeowner Survey

Resources 

• To apply for a permit to construct an ADU, fill out the ADU Completeness Checklist and a Building Permit application. The Building Permit application should be submitted online through the City's online permitting website: https://permits.redwoodcity.org/etrakit/  
• ADU Handout
• HCD ADU Handbook
• ADU Financing Guide by Casita Coalition
• CAL Housing Finance Agency Grant Program
• HIP Housing Home Share Program
• ADU Ordinance Adoption: 
  • Planning Commission (06/15/21)
  • City Council 1st Reading (08/23/21)
  • City Council 2nd Reading (09/13/21)

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