Walnut Creek has adopted a Zoning Ordinance covering ADUs


ADU applications do not require a public hearing and are reviewed through the Building Permit process. Some projects may also require a Site Development Permit or Tree Removal Permit. If an addition would trigger the Oversized Home Ordinance or Hillside Performance Standards, then an ADU is only permitted through the conversion of existing floor area.

ADUs are allowed in all residential districts with a single family home on the lot with no more than one ADU permitted per lot.

The maximum size for an ADU is 700 square feet of floor area. ADUs attached to the main unit cannot exceed 50 percent of the living area of the main unit.

One parking space will be required for the new construction of an ADU, in addition to the parking required for the main house. Parking can be provided on the lot as either a covered, uncovered and/or tandem space. No parking will be required for an ADU if it is located within one-half mile of a BART station or a public bus stop.

Local utility contacts:

Contra Costa Water District, Customer Service: (925) 688-8044

East Bay Municipal Utility District, New Business Office: (510) 287-1008

Central Contra Costa Sanitary District, Permit Team: 925-229-7371

For more information on ADUs, contact the Duty Planner at dutyplanner@walnut-creek.org or at 925-256-3558