Accessory Dwellings

All accessory dwellings must comply with the following standards:

A. An accessory dwelling may be created within an existing principal dwelling or accessory structure on the property; may be added to a principal dwelling or accessory structure; or may be built as a structure separate from any existing structure on the property. The maximum allowable living area of the accessory unit is 640 square feet. “Living area” is the interior habitable area of the accessory unit including basements and attics but not including garages. Living area shall be measured from the interior side of the exterior walls of the building.

B. With the addition of an accessory dwelling unit, current parking standards at the time of the addition must be met for both the principal and accessory dwelling unit.

C. Accessory dwellings must be permanent structures located on a permanent foundation.

D. Accessory dwellings attached to the principal dwelling must comply with the principal dwelling setbacks of the zoning district. Detached accessory dwellings must comply with the setbacks of accessory structures.

E. One (1) off-street parking space shall be provided for each bedroom or other room suitable for sleeping purposes within the accessory dwelling. This parking requirement shall be in addition to the requirement for the principal dwelling.

F. An accessory dwelling shall have a minimum of one hundred (100) square feet of usable open space.

G. An accessory dwelling shall be designed to be compatible with or exceed the architectural richness of existing development in the immediate vicinity or principal dwelling on the site. This shall include, but not be limited to, architectural features, colors, and building materials. New accessory dwellings constructed above the ground floor shall be designed to reasonably preserve the privacy of adjacent property owners.

H. An accessory dwelling may be approved prior to construction of the principal dwelling if in conjunction with the concurrent development of four or fewer parcels.

Summary of Petaluma ADU Requirements