Attached ADU

Most likely!

Local agencies may, by ordinance, designate where ADUs are permitted within zones that allow residential use.

However, any limits on where ADUs are allowed may only be based on the adequacy of water and sewer service and on the impacts on traffic flow and public safety.

If a lot with a residence has been rezoned to a use that does not allow for residential uses, that lot is no longer eligible for an ADU.

Under SB9, you may have two attached ADUs in your property.

When a lot split has not occurred, the lot is eligible to receive a second primary unit on the lot and to receive up to two ADUs under State ADU Law. When a lot split occurs, each lot is eligible for up to two units, including, for example, a primary unit and an ADU or JADU.

For single-family lots, local agencies must allow at least one ADU constructed from existing space, one JADU, and one newly constructed detached ADU.

For multifamily lots, local agencies must permit at least one ADU constructed from existing non-livable space (or up to 25 percent of the number of multifamily units), and up to eight detached ADUs (not to exceed the number of existing units on the lot.)

Examples of attached ADUs include, but are not limited to:

• An ADU addition to a duplex.

• An ADU built on top of an attached garage.

• ADU built as a new second story of a single-family dwelling.

• An ADU built in a newly constructed basement.

Your local government may have established specific minimum and maximum unit size requirements. It is best to consult with them or with an ADU Expert in your area.

Generally, maximum unit size requirements must allow an ADU of at least 850 square feet, or 1,000 square feet for ADUs with more than one bedroom.

For local agencies without a compliant ADU ordinance, up to 50 percent of the floor area of the existing primary dwelling for an attached ADU (at least 800 square feet) is permitted.

Local agencies must not establish by ordinance a minimum square footage requirement that prohibits the development of an efficiency unit. An efficiency unit may be as small as 150 square feet in floor.

There is no height limit contained in State ADU Law, but your local agency may impose specific height limits. However, they should not impose a limit that is less than 25 feet or the height limitation that applies to the primary dwelling whichever is lower.

It is best to consult with your local agency or with a knowledgeable ADU Expert in your area.

Yes. A setback of no more than four feet from the side and rear lot lines shall be required for an attached ADU. Additional setback requirements may be required in the Coastal Zone if required by a local Coastal Program.

None. You may choose to not even have a bedroom in your ADU, depending on your needs. A limit on the number of bedrooms could be construed as a discriminatory practice towards protected classes, such as familial status, and would be considered a constraint on the development of ADUs in the State.

Only when sprinklers are required for the existing primary residence. Installation of fire sprinklers shall not be if sprinklers are not required by building codes for the existing primary residence. For example, a detached single-family home designed and constructed decades ago would not have been required to have fire sprinklers installed under the applicable building code at the time. However, if the same primary dwelling recently underwent significant alteration and is now required to have fire sprinklers, any ADU created after that alteration must be provided with fire sprinklers.

Additionally, the construction of an ADU shall not trigger a requirement for fire sprinklers for the primary residence.

If a primary dwelling currently does not have fire sprinklers, and an attached ADU is proposed which would trigger fire sprinkler requirements due to the increase in livable space, that requirement shall not be imposed upon the primary dwelling unit.

No. A local agency cannot impose an owner-occupancy requirement on any ADU.

Local agencies may not deny a permit for an unpermitted ADU created prior to January 1, 2020.

An inspector from the local agency may inspect the unit for compliance with health and safety standards and provide recommendations to be compliant and obtain a permit. If the inspector finds noncompliance with health and safety standards, the local agency shall not penalize an applicant for having the unpermitted ADU and shall approve necessary permits to correct noncompliance.

However, the local agency may deny a permit if it finds that the building is substandard. This does not preclude the local agency from pursuing enforcement action on these violations, and an applicant may be required to make alterations or repairs accordingly.

You may consult with your local agency or our in-house ADU Expert at (408) 413-3373.

In the meantime, you may also read this ADU Handbook by the California Department of Housing and Community Development.