TranslateFrequently Asked Questions: ADUs and JADUs
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Accessory Dwelling Units & Junior Accessory Dwelling Units FAQs
What are the differences among an Accessory Dwelling Unit vs. a Junior Accessory Dwelling Unit vs. a guest house?
Sonoma County allows several types of residential accessory structures (see Policy 1-4-6, Residential Accessory Structures for a complete list). Below is a summary of the differences among a few of the most common residential accessory structures: Accessory Dwelling Units (ADUs), Junior Accessory Dwelling Units (JADUs), and guest houses.
| Structure Type | Accessory Dwelling Unit | Junior Accessory Dwelling Unit | Guest House |
|---|---|---|---|
| Structure | May be attached to or detached from the main dwelling or accessory structure | Must be created from, and within the footprint of, an existing or proposed single-family dwelling | Accessory building to a single-family dwelling which consists of a detached living area of a permanent type of construction |
| Kitchen | Must have a full kitchen (see Policy 1-4-5, Definition of a Kitchen) | Must have a small kitchen | Cannot have a kitchen or wet bar |
| Bathroom | Must have a full bathroom | Must have direct access to a bathroom, either inside the unit or in the main house | May have a half or full bath |
| Long-Term Rental | Can be rented | Can be rented | Cannot be rented or occupied separately from the main house |
| Transient Rental | May not be used as a vacation rental | May not be used as a vacation rental | May be able to be used as part of a vacation rental or hosted rental with a zoning permit |
| Z Combining District | Prohibited in the Z Combining District | Allowed in the Z Combining District | Allowed in the Z Combining District |
| Size Limit | 1,200 square feet | 500 square feet | 640 square feet |
| Permits Required | Building permit | Building permit | Building permit |
| More Information | Accessory Dwelling Units | Junior Accessory Dwelling Units | 1-4-6 Detached Residential Accessory Structures |
| Zoning Code Reference |
Section 26-88-060 of the Sonoma County Zoning Ordinance. See the County’s ADU website for more information and resources. |
Section 26-88-061 of the Sonoma County Zoning Ordinance. See the County’s JADU website for more information and resources. |
"Guest house" Ordinance No. 6335, 26-4-020, Section G-6 |
Does my property qualify for an accessory dwelling unit (ADU)?
If your property is within a single-family or multifamily zone, has an existing or proposed dwelling, and can provide adequate water supply and sewer or septic capacity, it may qualify for an ADU.
Zoning
Most residential zoning districts allow one accessory dwelling unit unless there is a "Z" (Accessory Dwelling Unit Exclusion) overlay zoning on the property. Accessory dwelling units cannot be used for vacation rentals or other transient occupancy.
Parcel Size Requirements
There is no minimum lot size for an accessory dwelling unit, but adequate water and sewer or septic must be demonstrated.
Permits
Approval of a Zoning Permit is usually required.
More Information
- Accessory Units and Junior Units
- Detailed requirements: Section 26-88-060 of the Zoning Ordinance (Note: (j)(2) Is no longer in effect. There is now no minimum parcel size requirement.)
Does my property qualify for a junior accessory dwelling unit (JADU)?
Structure
A Junior Unit is a very small living unit within a single-family dwelling. It’s created by adding an efficiency kitchen (see "Efficiency kitchen" Sec. 26-02-140) and exterior door to an existing, legal bedroom. It may include a bathroom or may share a bathroom with the house.
Occupancy
The property owner must live in the house or the Junior Unit. Neither the house nor the Junior Unit can be used for a vacation rental or other transient occupancy.
Zoning
Junior Units are allowed in every zoning district that allows a single-family dwelling.
Permits
Approval of a building permit is required.
More Information
- Accessory Units and Junior Units
- Detailed requirements: Section 26-88-061 of the Zoning Ordinance
Can I have both an Accessory Dwelling Unit AND a Junior Accessory Dwelling Unit on my parcel?
Yes. If the parcel qualifies for both types of accessory units, it may have one of each.
Can my non-bedroom space be converted into a legal bedroom and then into a Junior Accessory Dwelling Unit?
Yes, subject to these requirements for the non-bedroom space:
- It shares at least one full wall with the existing single-family dwelling.
- It is converted into a new legal bedroom. This includes meeting all permit requirements (e.g. Building Permits, Well and/or Septic permits, etc.).
- The Building Permit for the new bedroom has been finaled.
If those conditions are met, then you may apply to have the bedroom converted into a Junior Accessory Dwelling Unit.
Can I add a new bedroom outside the existing footprint of my single-family dwelling and then convert it into a Junior Accessory Dwelling Unit?
Yes, subject to these requirements for the new bedroom addition:
- The new bedroom must share at least one full wall with the existing single family dwelling.
- It meets the standards of a new legal bedroom. This includes meeting all permit requirements (e.g. Building Permits, Well and/or Septic permits, etc.)
- The Building Permit for the new bedroom has been finaled.
If those conditions are met, then you may apply to have the bedroom converted into a Junior Accessory Dwelling Unit.
Can accessory dwelling units (ADUs) be used for vacation or short term rentals?
ADUs may not be rented for periods of less than 30 days or used as vacation rentals.
Who can live in an accessory dwelling unit (ADU)?
Anyone can live in an ADU and they are not required to be occupied by an owner or relative of the owner.
How much are permitting fees?
Prior to issuance of the building permits for any ADU, the following fees are typically required:
- Development impact fees (e.g.: school, park, and traffic impact fees)
- Sewer and water connection fees (if new connections are created)
- Well and septic plan check and permit
Potential Fee Reductions
Permit fees are typically reduced for many ADUs and JADUs and can vary between roughly $15-35,000. Units built within the existing footprint of a single-family residence or accessory structure are not subject to sewer or water connection fees or capacity charges.
Traffic and parks mitigation fees in particular are reduced based on the size of the unit:
| Size of Unit (square feet) | Percent of Development Impact Fees Assessed |
|---|---|
| Up to 750 | 0% |
| 751-1,000 | 50% |
| 1,001-1,200 | 100% |