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Frequently Asked Questions

Accessory Dwelling Units & Junior Accessory Dwelling Units

What is the difference between an Accessory Dwelling Unit vs. a Junior Accessory Dwelling Unit vs. a guest house?

Structure TypeAccessory Dwelling UnitJunior Accessory Dwelling UnitGuest House
StructureMay be attached to or detached from the main dwelling.Must be created from, and within the footprint of, an existing, legally permitted bedroom that shares at least one full wall with the rest of the home.Accessory building to a single family dwelling which consists of a detached living area of a permanent type of construction.
KitchenMust have a full kitchen.Must have an efficiency kitchen. (see "Efficiency kitchen" Sec. 26-02-140)Cannot have a kitchen or wet bar.
BathroomMust 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 RentalCan be rented.Can be rented.Cannot be rented or occupied separately from the main house.
Transient RentalMay 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 DistrictProhibited in the Z Combining District.Allowed in the Z Combining District.Allowed in the Z Combining District.
Size LimitCannot exceed 1,200 square feet.Cannot exceed 500 square feet.Cannot exceed 640 square feet.
PermitsUsually requires a Zoning Permit.Allowed with a Building Permit in all zones where residences are allowed.Allowed with a Building Permit in all residential and agricultural zones.
More InformationAccessory Dwelling UnitsJunior Accessory Dwelling UnitsPJR-012 Guest House
Zoning CodeSec. 26-88-060 (Note: (j)(2) Is no longer in effect. There is now no minimum parcel size require­ment.)Sec. 26-88-061"Guest house" Sec. 26-02-140


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


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


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 7500%
751-1,00050%
1,001-1,200100%

Find out more about estimated permitting fees

Contact Information

Contact Planning by Phone
Monday – Friday
10:00 AM – 12:00 PM
1:00 PM – 3:00 PM
Address
2550 Ventura Avenue
Santa Rosa, CA 95403
38.465074, -122.723705

Calculator

ADU Calculator (beta)

Junior Unit

Try this new online tool to help estimate the costs, returns, and benefits associated with building an ADU.

Fire Prevention & ADUs

Fire Prevention Information on Accessory Dwelling Units

Fire Prevention and HazMat

Requirements for ADUs including fire access, sprinklers, and more.

Sonoma County Housing Authority

Resources for Property Owners

Hands forming house

If you plan to rent your ADU, consider participating in the Housing Authority's Housing Choice Voucher program and being a part of the solution to the County's affordable housing crisis.

State ADU Law

California Department of Housing and Community Development's web site describing state laws and regulations about Accessory Dwelling Units.

View State Web Site

Housing Initiatives

Permit Sonoma Housing Initiatives

Housing Initiatives

Permit Sonoma is introducing several initiatives to help meet the County's housing production goals.

Housing for All Strategy

Learn More

multi-unit housing

The County's strategic priority to ensure housing for all income levels.