Sonoma County · California
Sonoma ADU guide: local rules, permits & property planning
The City of Sonoma’s pre-reviewed plan program is separate from Permit Sonoma’s county jurisdiction. Begin by confirming that the property is inside city limits before selecting a drawing or application checklist.
Local planning guide · Reviewed October 2, 2026
What matters for an ADU in Sonoma
Permitting authority: City of Sonoma — ADUs
Official local guidanceLocal rules and design checks
| Topic | Local guidance |
|---|---|
| Responsible agency | Use City of Sonoma materials for an incorporated-city parcel; a Sonoma mailing address alone does not establish City jurisdiction. |
| Pre-reviewed designs | The City program reviews submitted designs for California Building Code compliance; property-specific work still accompanies the chosen plan. |
| Available plan range | The City’s program announcement identifies designs from 500 to 1,200 square feet. |
Selected local requirements, not a complete zoning determination. Confirm the current rules for your address with the responsible agency.
Fees and budget checks
Request the City’s site-specific permit and plan-check charges and ask the designer for plan-use pricing. The program says 150–499-square-foot plans are not yet available; do not budget a small-plan fee exemption around a catalog option that has not been posted.
Sonoma pre-reviewed ADU plans programHow to start the permit process
Confirm City jurisdiction, select a program design or custom approach, and use the City’s preapproved-plan checklist to establish the required building application materials.
Plan resource
Sonoma’s 500–1,200-square-foot plan collection
The City announced this range of pre-reviewed designs. Review the current collection and the designer’s terms before purchasing drawings.
View the original sourceSonoma ADU questions
- Should I start with Permit Sonoma?
- Only if the property is under County jurisdiction. Check the boundary before using county rules for a City of Sonoma project.
- Does the City already offer a plan under 500 square feet?
- The reviewed program page says the 150–499-square-foot options are not yet available. Ask about current additions.
Sources for this guide
- City of Sonoma — ADUs
- Sonoma pre-reviewed ADU plans program
- Sonoma’s 500–1,200-square-foot plan collection
- Sonoma preapproved-plan checklist
Local sources reviewed October 2, 2026. Historical examples retain their stated dates. Contact ADU California to confirm project availability; this guide does not establish an office location or property approval.
A useful first review
Separate what is available from what still needs verification.
01
Confirm the property
Start with a complete address and review the available parcel, building, and map context.
02
Identify the unknowns
Keep missing setbacks, easements, utilities, access, hazards, and local requirements visible.
03
Choose the next review
Use the preliminary result to prepare a focused conversation with the required professionals and agencies.
Explore project types
Compare the scope before choosing a solution.
These pages explain the questions each project type introduces. They do not assert that a particular scope is permitted or suitable for your address.
Compare planning footprints
See common ADU sizes before choosing a design.
These model pages are planning references only. They are not a statement that a particular size is allowed or buildable at a Sonoma address.
California directory
Explore more city guides.
The next useful action
Put your address at the center of the conversation.
The online review is preliminary and is not a permit decision, survey, engineering opinion, construction document, final price, or guaranteed schedule.