Building an ADU or JADU

Zoning, existing structures, and site conditions are a few matters that can impact your ability to have an ADU or JADU on your lot.

• Review Standards for ADUS and JADUs to determine if, where, how many, and what kinds of accessory units may be allowed on your lot.
• Use your knowledge of the intended site and the parcel search tool in our Zoning and Land Use Map Viewer to help navigate applicable standards.

Required fees and construction costs may determine the financial feasibility of building an ADU or JADU.

• Will you need to hire a qualified septic consultant, architect, and/or other specialist? Be sure to include labor costs during the preliminary phases as well as during the construction phase in your budget.
• For Permit Sonoma fee information, refer to ADU Fees and Permit Sonoma Fee Schedules.
• Incentives may apply for ADUs with recorded Affordable Housing Agreements. See Article 89-Affordable Housing Program Requirments and Incentives for more information.
• The Napa Sonoma ADU Center provides additional resources for budgeting and financing options.

In addition to financial feasibility, consider the following:

• Goals. Your specific vision for the unit will impact its broad and fine scale design.
  • Are you looking to convert an existing structure, or want to create something entirely new?
  • Who are your intended occupants? (see Step 6a Who will occupy your ADU or JADU?) Owner-occupancy requirements may apply.
  • If renting, how will you balance income potential with tenant costs? Including or excluding certain appliances or finishes may impact desirability and affordability.
  • What's your desired aesthetic? Materials, layout, and natural light can all affect the feel of your unit.
• Standards and Site Constraints. Review Standards for ADUs and JADUs to determine if, where, how many, and what kinds of accessory units may be allowed on your lot. Use your knowledge of the intended site and the parcel search tool in our Zoning Map Viewer to help navigate applicable standards.
• Insurance Requirements. Insurance companies often have specific requirements for insurability of your structure against fire or flood. You may wish to consult with your anticipated insurance provider so that you can integrate requirements into your design.
• Streamlining. Consider using pre-reviewed, factory built, or manufactured plans to save time, money and effort designing and permitting new detached ADUs. However, even when using one of these options certain project-specific standards will still need careful attention as you integrate these plans with your site. Resources:
  • ADU Ready Pre-reviewed ADU Plans
  • Policy 4-0-9 Factory Built Housing Permits
  • Policy 4-0-10 Placement of Manufactured Homes on Private Property
• Professional Assistance. Whether using one of the streamlining options or designing an ADU or JADU from scratch, working with a professional through at least some of the design process is recommended. Owner-builders should review form CSS-026 Owner-Builder Information and Authorization.

4a. What Permits do I need?

• It is highly recommended and sometimes required that you work with a professional to obtain required permits. Owner-builders assume full responsibility for obtaining all necessary permits and should review form CSS-026 Owner-Builder Information and Authorization.
• At a minimum, a building permit (BLD) is required to establish an ADU or JADU. However, additional permits may be required depending on the project scope and site conditions.
• Before applying for a building permit, review Standards for ADUs and JADUs to help evaluate the following considerations.
  • Is a planning permit required? If so, obtain all planning permits prior to submitting your building permit application.
  • Can adequate water supply be demonstrated? Water requirements vary based on the type of water service and location. Obtain any necessary testing, evidence of water service, and associated permits before applying for a building permit.
  • Can adequate wastewater disposal capacity be demonstrated? Obain any necessary testing, evidence of wastewater disposal capacity, and associated permits before applying for a building permit.
  • Do I have adequate emergency access? Consult with our fire prevention division before applying for a permit.
  • Will you be doing any grading or encroaching in the right-of-way? Grading and/or encroachment permits may be required.
  • Are permits from other agencies required? See CSS-027 Notice to Recipients of Ministerial Permits for more information.

4b. Applying for permits.

Once the above considerations have been addressed via any required testing, permits, evidence of service, or other items, submit a building permit application.

• Owner-builders accept full responsibility for all permits, standards, and fees applicable to their project and should review form CSS-026 Owner-Builder Information and Authorization.
• Apply Online. Visit our online permitting website (Permits Online) to submit a building permit or other development permit application.
• Building Permit (BLD) Application Requirements. Complete application requirements may vary depending on where the proposed unit is located. Ensure all required testing and preliminary permits are complete prior to submitting your building permit application (see What permits do I need?). Minimum BLD application requirements are listed below:
  • Refer to BPC-021 Residential Building Permit for Projects that Require Plans and BPC-002 Residential Plan Checklist for application requirements and procedures.
  • Site plans must conform to:
    • CSS-019 Minimum Standard Site Plan Requirements for Building & Engineering Applications; and
    • PJR-129 Site Plan Requirements for Planning Applications; and
    • ADU Fire Prevention site plan requirements.
  • If proposing construction within a front yard, scenic corridor, or other front setback area: provide a diagram and calculations showing the location of the setback line and interior square footage of the proposed unit on either side of the setback line. See Standards for ADUs and JADUs for more information.
  • If using pre-reviewed, factory built, or manufacturedplans:
    • Ensure all plans and diagrams clearly delineate site-built components from pre-reviewed, factory built, and manufacture components.
    • For pre-reviewed ADU plans, refer to 4-0-12 ADU Ready Checklist (Coming Soon!).
    • For factory built ADUs, refer to 4-0-9 Factory Built ADU Permits.
    • For manufactured ADUs, refer to 4-0-10 Placement of Manufactured Homes on Private Property.
  • If building site evaluation is required:
    • Building site evaluation will confirm whether additional reports or studies (such as a geotechnical report) are necessary to complete your permit application.
    • If needed, site evaluation must be done, and any subsequently required documentation must be provided in order to consider your application completed.
    • Initial fees must be paid before site evaluation can begin.
    • See 4-0-2 Building Site Evaluation for more information.
  • If you are an owner-builder: Include a complete CSS-026 Owner-Builder Information and Authorization in your application.
  • If using an ADU to defer fees on your single-family dwelling: An affordable housing agreement is required. See our Single-Family Development Fee Deferral Program for more information.
• Pay Initial Fees. Your application will begin with the intake team who will invoice initial review fees and provide a first glance at missing submittal items.
  • Pay fees through our online portal (Permits Online).
  • See ADU Fees and Permit Sonoma Fee Schedules for more information.

4c. Permit Sonoma will begin review once initial fees are paid.

• Building Site Evaluation. If required, a Permit Sonoma  building inspector will conduct a site evaluation and request additional reports or studies if necessary to complete the application.
• Plan Review. Once complete, your application will be reviewed by the building plans examiner and staff from other affected divisions for compliance. If necessary, issues to be addressed will be provided through our Digital Plan Room.
  • If pre-reviewd plans are used, the plans examiner will review all limitations on use of stock plans in relation to the project specific design.
• Review Timelines. Applications will generally be approved or denied within the following timelines once deemed complete:
  • 60 days for general applications; or
  • 30 days for applications using pre-reviewed, factory built, or manufactured plans.

4d. Address issues and resubmit (if required).

After all divisions have reviewed your application, and if any issues were identified, you will need to address all issues by submitting updated plans or other requested documents that demonstrate compliance.

4e.  Pay fees for permit issuance.

Once your application has been approved  by all affected divisions, fees necessary for permit issuance will be assessed. Following payment, your building permit can be issued.

• Some fees are a flat rate while others may be assigned based on the valuation of the project, square footage, or other measurements.
• See Fee Information for ADUs and JADUs and Permit Sonoma Fee Schedulres for more information.

4f. Make revisions (if desired).

If you change your mind on your design after your building permit has been issued, you may apply for a revision to your building permit.

• See Revisions to Issued Building Permits for more information.

5a. Hire a contractor. 
If you are not a licensed contractor or already working with a design/build firm, it is highly recommended that you hire one for the construction phase of your ADU or JADU. 

• If you are an owner-builder choosing to construct your own unit, ensure you have reviewed and submitted a complete CSS-026 Owner-Builder Information and Authorization.

5b. Begin construction and schedule inspections.
Begin construction within a year from building permit issuance, or the issued permit will expire. Once your ADU or JADU is under construction, schedule the appropriate inspections. 

• Some inspections must occur while construction is underway while others must occur after construction is finished. 
• See Inspections for more information.

5c. Pass inspections. 
Your ADU or JADU must pass all inspections to receive a certificate of occupancy. Required inspections may include but are not limited to:

• Grading
• Compaction
• Site Utilities
• Foundation
• Interior Elements
• Exterior Elements
• Fire Prevention
• CALGreen – Performed by third party special inspectors, not Permit Sonoma staff 

5d. Record deed restrictions (if required).
Deed restrictions must be recorded for the following before a certificate of occupancy can be issued:

• ADUs used to defer affordable housing fees on a single-family dwelling.
  • An Affordable Housing Agreement must be recorded. 
  • See our Single-Family Development Fee Deferral Program for more information.
• All JADUs.
  • A JADU Declaration of Restrictions 2026 (PDF) must be recorded that: 
    • Prohibits sale of the JADU separately from the single-family residence; and
    • Specifies that the deed restriction runs with the land and is enforceable against future property owners; and
    • Restricts the size and attributes of the JADU to those established by Government Code Section 66333 and County Code Section 26-24-190; and
    • Makes the County a third-party beneficiary of the deed restriction with the right to enforce the provisions of the deed restriction. 
  • You will need the legal description of your property (the description of the parcel from your deed). 
  • Submit the form with the application for a building permit and a planner from the Planning Division will sign it and return it to you.
  • Planning will place a hold on the final inspection pending receipt of the recorded form. 
  • Have the form notarized. 
  • Record the completed form with the County Recorder's office. Ask for a conformed copy. 
  • Return the conformed copy to the Planning Division by email so they may remove the hold.

5e. Pay final fees and obtain a Certificate of Occupancy.
Once all final inspections have been passed and any necessary deed restrictions have been recorded, pay any remaining fees to receive a certificate of occupancy prior to inhabiting your ADU or JADU. 

• See Fee Information for ADUs and JADUs and Permit Sonoma Fee Schedules for more information.
• If using a manufactured home (mobile home): HCD Form 433(A) and HCD Form 433(B) must be completed by the applicant and recorded with the Sonoma County Recorder’s Office after installation and inspections before a certificate of occupancy can be issued. Refer to 4-0-10 Placement of Manufactured Homes on Private Property.
  • Applicants are responsible for recordation fees and HCD transportable unit fees.

6a. Who will occupy your ADU or JADU?

• Owner-Occupancy Requirements for JADUs. Property owners must reside in either the JADU or the remaining portion of the primary residence unless either:
  • The JADU has a separate bathroom; or 
  • The owner is a governmental agency, land trust, or housing organization.
• Otherwise, you may choose to expand your pool of possible tenants. Friends, aging parents, adult children, and other family members are common ADU and JADU residents.

6b. Renting out your ADU or JADU?

• Preliminary Steps. If choosing to rent out your accessory unit, prepare by obtaining insurance, setting up utilities, and developing a plan for handling finances.
• Understand Rental Laws. Be sure to understand the rules and responsibilities of becoming a landlord.
  • California Tenants Guide
  • California Landlord Resources
• Set the Rent. Consider offering your ADU as a deed-restricted affordable unit. Incentives may apply for ADUs with recorded Affordable Housing Agreements. See Article 89 – Affordable Housing Program Requirements and Incentives for more information.
• Rental Duration. All ADUs and JADUs must be rented for periods of more than 30 days at a time, meaning they are prohibited from use as vacation rentals, hosted rentals, or other short-term rentals.

6c. Separate Sale.

• ADUs may be rented but not sold or otherwise conveyed separately from the primary residence except as specifically provided for by State law (see Government Code Section 66341). 
• State ADU Law additionally authorizes local jurisdiction to choose whether to allow the separate sale of ADUs as condominiums (Government Code Section 66342, enacted by AB 1033). However, the County has not yet adopted an ordinance to allow this.
• JADUs are prohibited from being sold separately from the primary dwelling.