Coastal Zone ADUs

Accessory dwelling units (ADUs) in the Coastal Zone are referred to as “second dwelling units” or “second units”. Parcels in the coastal zone are notated by a “CC” designation which may be looked up using our Zoning and Land Use Map Viewer. Sec. 26C-325.1 of the Sonoma County Municipal Code provides guidelines for the development of second dwelling units in the Coastal Zone. Some highlights are listed below.

What permits are required?

If allowed by zoning, second dwelling units in the coastal zone require at minimum a building permit (BLD), coastal permit (CPH or CPN), and either a use permit (UPE) or zoning permit (ZPE). Additional permits such as those for grading, encroachment, water, and sanitation may be required.

• Use Permit (UPE) Required: Parcels with Land Intensive Agriculture (LIA) or Land Extensive Agriculture (LEA) base zoning.
• Zoning Permit (ZPE) Required: Parcels with all other base zones besides LIA or LEA.

Development Standards for Second Dwelling Units

Septic requirements, water availability, and construction standards applicable to inland ADUs are also applicable to coastal second dwelling units. 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.

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

1. Look up your parcel using our ADU 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.