Accessory Dwelling Units (ADU)

Accessory Dwelling Units (ADU) & Junior Accessory Dwelling Units (JADU)

An Accessory Dwelling Unit (ADU) is a small, independent residential unit located on a property with single or multi-family residential development potential.  In 2017 and 2019 the State legislature passed laws to ease development standards and facilitate their construction. Since 1/1/2020, California allows by right ADUs on single- and multi-family unit properties.  State code 65852.2 sets a threshold for the number, size and location of ADUs on a property but local agencies can add development restrictions and standards where the state law is silent.

General Information- Check current ordinances

Local ADU ordinances that do not comply with state law become null and void, making the government code the ruling ordinance.  Santa Barbara and Goleta have adopted new ordinances.  Santa Barbara County is in the process of adopting a new ordinance. Carpinteria has not begun the process of adopting a new ordinance. For properties in the coastal zone, the government code applies until the jurisdiction’s Local Coastal Plan (LCP) is updated to address ADU’s in the coastal zone and is approved by the Coastal Commission.

In general, new ADUs can be located 4’ from the side and rear property lines but not in the front yard setbacks.  Existing, legal, non-conforming structures like garages can be converted regardless of their location and enlarged with certain limitations. Garage conversions do not require that parking be replaced.  Parking for ADUs is not required if the property is within ½ mile from a transit stop.  Uncovered parking is allowed in an existing driveway.

For properties zoned for multi-family residential development, state law allows for conversion of accessory structures (i.e., garages, laundry rooms, storage, and mechanical) to create new ADUs up to 25% of the number of existing residential units.  Example – If there are 8 existing units, 2 ADUs could be added.

In addition to ADUs, which are separate structures, state law also allows for the creation of Junior Accessory Dwelling Units (JADUs) which are contained within the main house (dwelling).  A JADU cannot exceed 500 square feet, must have an independent entrance, and have minimal cooking facilities. The JADU can share a bath with the main dwelling. The JADU does not require a 1-hour/45 dB fire and sound separation as required of ADUs.  The JADU can share the main dwelling furnace but needs separate return air systems.

The maximum floor area and height of an ADU varies according to jurisdiction, type, zoning and location. There is no maximum size for conversions of existing structures, but other restrictions may apply.  According to different scenarios, new ADUs may be up to 1,000 sf; up to 1,200 sf; or no more than 50% of the size of the existing main dwelling.  Some jurisdictions apply restrictions based on lot area, the existing additional accessory buildings on the property, and the open yard area required for the main dwelling.  Santa Barbara’s solar ordinance restricts height along the north property line.

Since 2020, state law also allows for the construction or conversion of one ADU plus one JADU on most properties with specific maximum floor area and height.  Standards also vary if the property is located within the coastal zone or in high fire areas and where, as a general rule, additional parking may be required.  Owner occupancy is no longer required for ADUs, but it is required for JADUs. Most local ordinances require rental terms of at least 31 days to eliminate their use as short term vacation rentals.

Properties with septic systems (Onsite Wastewater Treatment System (OWTS):  Contact the County Environmental Health Services (EHS) and review specific requirements as a first step in process as costs may make the project infeasible. In addition, properties located  in “Special Problem Areas” may require supplemental treatment and an expense that could make the project infeasible. More info here.

In summary, development standards for accessory dwelling units vary according to jurisdiction, unit type, location.

Zoning Information 

Tips for Building Department Plan Checking 

An application that complies with the local (or state, if applicable) ADU ordinance can be submitted directly to the building division and must to be approved within 60 days once it is deemed “complete”.  Some typical issues that must be resolved for a “complete” application are as follows:

Conversion of existing structures:  Conversion of existing, legally permitted habitable spaces (i.e., dens, hobby rooms or bedrooms) are not required to meet current building codes while additions and new structures do.  If the existing structure was permitted as a non-habitable space (i.e., garage, storage, barn) the proposed conversion constitutes a change of use and requires compliance with current structural and energy codes.

Title 24 Energy compliance is required for new and change-of-use applications. Solar panels are required for detached ADUs.

Soils Report is required for detached ADUs, 2^nd story additions, and single-story additions that are over 500 sf.  Waivers may be granted in special circumstances.

Existing footings must be 12” wide minimum continuous footing with 12” embedment into firm soil.  Substandard footings may be underpinned.

High fire/fire separation requires standard high-fire construction.  1-hour, 45-STC fire and sound assemblies are required at shared walls and ceiling.  A garage conversion within 5’ of a property line may require wall and eave upgrades to meet 1hr fire construction.

Fire sprinklers are not required if the main residence does not have sprinklers.

Utilities – Separate electrical subpanel, HVAC, and water heater are required for ADUs  JADU’s may share existing.  Separate meters are not required for ADUs.

Resources