Coastal Zone ADUs

Accessory dwelling units (ADUs) in the Coastal Zone are referred to as “second dwelling units” or “second units” in the Coastal Zoning Code (Chapter 26C). Junior accessory dwelling units (JADUs) are not yet provided for in the Coastal Zone. Parcels in the Coastal Zone are notated by a “CC” designation which may be found by using our  Zoning and Land Use Map Viewer to look up your parcel.

Sec. 26C-325.1 of the Sonoma County Municipal Code provides guidelines for the development of ADUs in the Coastal Zone. Some highlights are listed below.

What permits are required?

If allowed by zoning, ADUs in the Coastal Zone require at minimum a building permit (BLD), and either a use permit (UPE) or zoning permit (ZPE). A coastal development permit (CPH or CPN) and additional permits such as those for grading, encroachment, water, drinking water and sanitation may be required depending on the project location and scope.

• Use Permit (UPE): Required for parcels with Land Intensive Agriculture (LIA) or Land Extensive Agriculture (LEA) base zoning.
• Zoning Permit (ZPE): Required for parcels with all other base zones besides LIA or LEA.
• Coastal Permit with Hearing (CPH) or Coastal Permit with No Hearing: Ask a planner which may be required for your specific location and project scope by emailing Planner@sonomacounty.gov with as much detail as you can provide.
• Water and Sanitation Permit Requirements: Ask our Well and Septic staff for onsite systems or Engineering staff for public utility connections.

Standards for Coastal ADUs

Septic requirements, water availability, and construction standards applicable to inland ADUs are also applicable to coastal ADUs. However, certain restrictions such as number of allowed units, lot size requirements, square footage, setbacks, and more are different depending on specific parcel zoning and coastal standards for second dwelling units. Development in the Coastal Zone must be consistent with the adopted Local Coastal Plan as well as any easements, building envelopes, or other standards applicable to your specific parcel.  It is highly recommended that you hire a professional to assist you through the permit process and that you consult with Permit Sonoma staff either online or at our Permit Center regarding your specific proposal.

How do I find my coastal parcel’s zoning standards?

1. Look up your parcel using our Zoning and Land Use Map Viewer.
   • Note the zoning designations for base zoning and any overlaying combining districts.
   • Base zoning will include designations such as LIA, LEA, DA, RR, R1, R2, etc.
   • Combining districts will include designations such as F1, F2, SR, BR, HD, G, MR, and Z
2. Go to Chapter 26C of the Sonoma County Municipal Code.
3. Find the Article(s) associated with your parcel’s zoning designation(s).
   • For example: Article IV. – DA CC Diverse Agriculture Coastal District and Article, Article XXII. – Scenic Resources Combining District
   • Note - some combining districts such as RC (Riparian Corridor) may be found in Chapter 26 of the Sonoma County Municipal Code if not listed in Chapter 26C.
4. Review your parcel’s zoning requirements in tandem with those established in 26C-325.1 – Second Dwelling Units.

Please Note: Additional standards beyond zoning will apply as discussed above.