Accessory dwelling units can be created in areas zoned to allow single-family or multifamily dwelling residential use. A coastal development permit may be required for accessory dwelling units within the coastal zone. Construction of a primary residence can be in conjunction with the construction of an accessory dwelling unit.
How many Accessory Dwelling Units Permitted on a property?
The number depends on the type of building is the Primary Residence:
a. An accessory dwelling unit is permitted on a lot with a proposed or existing single-family dwelling unit; or
b. Multiple accessory dwelling units are permitted within portions of multifamily buildings that are not used as liveable space including, but not limited to, storage rooms, boiler rooms, passageways, attics, basements, or garages; or
c. A minimum of one accessory dwelling unit, or up to 25 percent of the existing multifamily units, is permitted within an existing multifamily dwelling; or
d. Up to two detached accessory dwelling units shall be permitted on a lot with an existing multifamily dwelling.
First, start by checking how the zoning regulations influence the value of your property.
3. How large can an ADU be permitted on a lot?
As the rule-of-thumb for any accessory dwelling units, they have to be smaller than the primary residence. They have to follow these size requirements:
a. The total floor area for an attached accessory dwelling unit shall not exceed 50 percent of the total floor area of the proposed or existing primary residence, 850 square feet, or 1,000 square feet for a unit that provides more than one bedroom, whichever is greater.
b. An accessory dwelling unit of at least 800 square feet shall be permitted regardless of floor area ratio, lot coverage or open space requirements of the underlying zone.
c. The total floor area for a detached accessory dwelling shall not exceed 1,200 square feet.
d. An accessory dwelling unit within an existing accessory structure may be increased by a maximum of 150 square feet beyond the same physical dimensions as the existing accessory structure to accommodate ingress and egress.
4. Where can you build on your property?
Accessory dwelling units may be attached to or located within a proposed or existing primary residence or accessory structure (including attached garages, storage areas or similar structures). Accessory dwelling units may be detached from the primary residence.
5. Is there a maximum height for an ADU?
Yes, there is! An accessory dwelling unit, as measured from the ground, cannot exceed the height limit for the primary residence in accordance with the underlying zone, or 16 feet, whichever is greater.
California offers the option go through a streamlined permit process if the homeowners add more units on their single-family property. You can out if your project is eligible for the streamline permitting process under Senate Bill 9 (SB9) and how much you could build on the property by going through this check list.
How to get permits fast?
6. Here are few development exceptions you should know
Accessory dwelling units shall conform to the underlying zoning and land use development requirements for primary residences with the following exceptions:
a. A new attached or detached accessory dwelling unit is allowed a setback of no less than four feet from the side and rear lot lines.
b. A new detached accessory dwelling unit shall be located a minimum of six feet from a primary residence.
c. No setback shall be required for an existing garage, living area, or accessory structure constructed in the same dimensions that is converted to an accessory dwelling unit or to a portion of an accessory dwelling unit, and a setback of no less than four feet from the side and rear lot lines shall be required for an accessory dwelling unit that is constructed above an accessory structure.
d. Correction of nonconforming zoning conditions shall not be a condition for ministerial approval of a permit application for the creation of an accessory dwelling unit.
7. Is the parking required on the property?
Parking for an accessory dwelling unit is not required in any of the following instances:
a. The accessory dwelling unit is located within one-half mile walking distance of public transit.
b. The accessory dwelling unit is within an architecturally and historically significant historic district.
c. The accessory dwelling unit is part of the proposed or existing primary residence or an accessory structure.
d. The accessory dwelling unit is in an area where on-street parking permits are required, but not offered to the occupant of the accessory dwelling unit.
e. The accessory dwelling unit is located within one block of a car share area.
