California ADU Regulations Highlights
(Website in Construction)
According California Department of Housing & Community Development, Accessory Dwelling Units (ADUs) and Junior Accessory Dwelling Units (JADUs) are an innovative and effective option for adding much needed housing in California.
► ADUs are an affordable type of home to construct in California because they do not require paying for land, major new infrastructure, structured parking, or elevators.
► ADUs can provide a source of income for homeowners.
► ADUs are built with cost-effective wood frame construction, which is significantly less costly than homes in new multifamily infill buildings.
► ADUs allowextended families to be near one another while maintaining privacy.
► ADUs can provide as much living space as many newly-built apartments and condominiums, and they’re suited well for couples, small families, friends, young people, and seniors.
► ADUs give homeowners the flexibility to share independent living areas with family members and others, allowing seniors to age in place as they require more care.
Zoning and Development Standards
For other ADUs, local governments may, by ordinance, designate areas in zones where residential uses are permitted that will also permit ADUs. However, any limits on where ADUs are permitted may only be based on the adequacy of water and sewer service and on the impacts on traffic flow and public safety. Further, local governments may not preclude the creation of ADUs altogether, and any limitation should be accompanied by detailed findings of fact explaining why ADU limitations are required and consistent with these factors. 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 to create an ADU. ADUs that do not meet objective and ministerial development and design standards may still be permitted through an ancillary discretionary process if the applicant chooses to pursue this route. In this scenario, the applicant assumes time and monetary costs associated with a discretionary approval process.
Size Requirements
While local governments may impose certain development standards on ADUs, these standards shall not include minimum lot size requirements. Further, lot coverage requirements cannot preclude
the creation of a statewide exemption ADU. A statewide exemption ADU is an ADU of up to 800 square feet, 16 feet in height, as potentially limited by a local agency, and with four-foot side
and rear yard setbacks. State ADU Law requires that no lot coverage, floor area ratio, open space, or minimum lot size will preclude the construction of a statewide exemption ADU. Further,
State ADU Law allows the construction of a detached new construction statewide exemption ADU to be combined on the same lot with a JADU in a single-family residential zone. In addition, ADUs
are allowed in any residential or mixed uses regardless of zoning and development standards imposed in an ordinance.
A local government may, by ordinance, establish minimum and maximum unit size requirements for both attached and detached ADUs; however, 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 an ADU ordinance, maximum unit sizes are 1,200 square feet for a new detached ADU
and up to 50 percent of the floor area of the existing primary dwelling for an attached ADU (at least 800 square feet). The conversion of an existing accessory structure or a portion of the
existing primary residence to an ADU is not subject to unit size requirements. Maximum unit sizes can exceed 1,200 square feet for ADUs through the adoption of a local ADU ordinance. State ADU
Law does not limit the authority of local agencies to adopt less restrictive requirements for the creation of ADUs.
Setbacks
A local agency may impose development standards, such as setbacks, for the creation of ADUs. However, setbacks should not unduly constrain the creation of ADUs and cannot be required for
ADUs proposed pursuant to subdivision. Further, a setback of no more than four feet from the side and rear lot lines shall be required for an attached or detached ADU. Additional setback
requirements may be required in the Coastal Zone if required by a local Coastal Program. Setback requirements must also comply with any recorded utility easements or other previously recorded
setback restrictions. No setback shall be required for an ADU created within an existing living area or accessory structure or an ADU created in a new structure in the same location as an
existing structure, while not exceeding the existing dimensions, including height.
A local agency may also allow the expansion of a detached structure being converted into an ADU when the existing structure does not have four-foot rear and side setbacks. A local agency may
also allow the expansion area of a detached structure being converted into an ADU to have no setbacks, or setbacks ofless than four feet, if the existing structure has no setbacks, or has
setbacks of less than four feet, respectively. A local agency shall not require setbacks of more than four feet for the expanded area of a detached structure being converted into an ADU.
A local agency may still apply front yard setbacks for ADUs, but front yard setbacks cannot preclude an ADU of at least 800 square feet and must not unduly constrain the creation of all types of ADUs.
Parking Requirements
Parking requirements for ADUs shall not exceed one parking space per unit or bedroom, whichever is less. These spaces may be provided as tandem parking on a driveway. Guest parking
spaces shall not be required for ADUs under any circumstances. For certain ADUs, Local agencies may choose to eliminate or reduce parking requirements for ADUs, such as requiring zero
or half a parking space per each ADU, to remove barriers to ADU construction and to facilitate development. Local agencies should be flexible when siting parking for ADUs. Off-street
parking spaces for the ADU shall be permitted in setback areas in locations determined by the local agency or through tandem parking unless specific findings are made. Specific findings
must be based on specific site or regional topographical or fire and life safety conditions.
When a garage, carport, or covered parking structure is demolished in conjunction with the construction ofan ADU, or converted to an ADU, the local agency shall not require that those
off-street parking spaces for the primary unit be replaced.
Impact Fees
An ADU is exempt from incurring impact fees from local agencies, special districts, and water corporations if less than 750 square feet. If an ADU is 750 square feet or larger, impact
fees shall be charged proportionately in relation to the square footage of the ADU to the square footage of the primary dwelling unit. For purposes of calculating the fees for an ADU on
a lot with a multifamily dwelling, the proportionality shall be based on the average square footage of the units within that multifamily dwelling structure. For ADUs converting existing
space with a 150 square-foot expansion, a total ADU square footage over 750square feet could trigger the proportionate fee requirement. Agencies can waive impact and any other fees for ADUs.
Also, local agencies may use fee deferrals for applicants.
Impact fees charged for the construction of ADUs must be determined in accordance with the Mitigation Fee Act and generally include any monetary exaction that is charged by a local agency
in connection withthe approval of an ADU, including impact fees, for the purpose of defraying all or a portion of the cost of public facilities relating to the ADU. A local agency, special
district, or water corporation shall not consider ADUs as a new residential use for the purposes of calculating connection fees or capacity charges for utilities, including water and sewer
services. However, these provisions do not apply to ADUs that are constructed concurrently with a new single-family home.