Pre-Reviewed Accessory Dwelling Unit Program

The County of Sonoma’s new ADU Ready program encourages the construction of detached accessory dwelling units (ADUs) through the use of pre-reviewed ADU plans. The program not only responds to Government Code Section 65852.27 established with Assembly Bill 1332, but also supports goals for increasing housing as outlined in the Sonoma County General Plan. The program is intended to make the designing and permitting of ADU projects faster, easier, and more affordable.

How it Works

For a fee, licensed professionals can submit their ADU designs to Permit Sonoma for pre-review. These will be listed in our Pre-reviewed ADU Design Gallery if approved. People wishing to build an ADU can browse this gallery and contact the vendor of a listed design for an ADU plan package.

Either with the help of a professional and or following owner-builder requirements, applicants can integrate these ADU plans into a project-specific plan package to submit with their Building Permit application. Project applicants are responsible for licensing fees and limitations on pre-reviewed plan use as required by plan vendors. Once a complete Building Permit application is submitted and initial fees are paid, it is sent to the appropriate divisions for commentary. Permit Sonoma has 30 days to review the application for site- and project-specific items such as foundation plans, zoning consistency, and fire code compliance. Revisions may be requested based on these standards. Or, if all divisions find the application in compliance, the Building Permit will be marked as approved and final fees will be assessed. Once final fees are paid, the Building Permit will be issued, and construction may begin. After construction is complete and all inspections are passed, a certificate of occupancy will be issued and the ADU may be occupied.

Applicability

ADU Ready streamlining applies to new construction detached accessory dwelling units using unmodified pre-reviewed plans. Proposed variations from pre-reviewed plans may necessitate greater fees and processing time. Vendors listed in the Pre-reviewed ADU Design Gallery may still be able to provide inspiration or render services associated with designing a custom ADU if choosing not to use the program.

Coastal parcels. Parcels in the coastal zone (CC zoning designation) may use this program but require land use permit approval prior to submitting a building permit application. Refer to Sec. 26C-325.1 of the Sonoma County Municipal Code for coastal zoning standards for ADUs. ADUs in the coastal zone are referred to as “second dwelling units”.

• A Use Permit (UPE) is required for coastal parcels zoned LIA (Land Intensive Agriculture) or LEA (Land Extensive Agriculture).
• A Zoning Permit (ZPE) is required for coastal parcels zoned DA (Diverse Agriculture), RRD (Rural Resources & Development), RR (Rural Residential), AR (Agricultural Residential), R1 (Low Density Residential), R2 (Medium Density Residential) and R3 (High Density Residential).

Want to build an ADU using pre-reviewed plans?  

• Review PJR-149 Preliminary ADU Checklist.
  • Use our Parcel Search Tool and your knowledge of the site to navigate the checklist. 

• Check out our Pre-reviewed ADU Design Gallery.
  • Stick Built Designs. Building applications for ADUs using pre-reviewed stock plans with an “STK” reference number should include this number in their application proposal.
  • Factory Built Housing and Manufactured Homes. Factory Built and Manufactured Homes are subject to regulations set by the California Department of Housing and Community Development (HCD) and the U.S. Department of Housing and Urban Development (HUD). 

• • • Building applications for ADUs using factory-built designs should note the corresponding HCD insignia number in their application proposal.  

• • • Building applications for ADUs using manufactured homes should note the corresponding HCD placard number in their application proposal.  
• A checklist of submittal requirements and procedures is coming soon. In the meantime, contact Isabella Wotring at Isabella.Wotring@sonoma-county.org for submittal information.  
• Feel free to visit our Permit Center to meet with staff from each division.  

Considering submitting plans to add to our gallery? 

• Review ADU Ready Design Submissions. 

Project Applicant Benefits

• Less Time, Effort, and Money. From designing to permitting, pre-reviewed plans save time and work.
  • Designing: Integrating a pre-reviewed ADU plan into a site plan can lessen the load of compliance measures, plan drawings, and details the applicant and their design team have to focus on. This not only saves time but can reduce the overall cost of the project design.
  • Permitting: The timeline for review of an ADU building permit is normally 60 days. Under the ADU Ready program, this is cut in half to just 30 days. Since certain standards are already met through the pre-reviewed plans, the building division has less items to review. This means lower fees may be charged for projects using pre-reviewed plans.
• More Certainty. Though the applicant will still need to mindful of certain site and project-specific standards when choosing and integrating pre-reviewed ADU plans with their site, they can breathe knowing the plan details of the ADU itself have already been checked for code compliance. So long as proper due diligence is done before applying for a building permit, applicants using pre-reviewed ADU plans are less likely to be held up by unmet objective standards.

Plan Vendors Benefits

• Income. Once plans are approved as pre-reviewed, licensing fees for the same pre-reviewed ADU package may be sold repeatedly until the end of the code cycle.
• Client Reach. Vendors’ plans and contact information will be listed in our online gallery to be perused by potential ADU project applicants. Applicants may reach out to purchase a pre-reviewed ADU plan package, but they may also be looking for help with a custom ADU project outside of the ADU Ready program.

Partially Streamlined Review

Using pre-reviewed ADU plans reduces the load on the applicant and their team by providing a base template for the ADU itself. However, individual site conditions and constraints must still be addressed by the applicant including, but not limited to: foundation, wastewater, water, fire safe standards, and zoning requirements. As such, plans listed in the Design Gallery are referred to as “pre-reviewed” rather than “pre-approved”.

Updates Coming Soon

Permit Sonoma’s ADU webpage is undergoing major updates to better communicate the permitting process. Stay tuned for additional guidance and resources!