ADU Frequently Asked Questions Updated: Jun 11, 2024

Click HERE for the entire FAQs list about ADU. For the Spanish version please click HERE.

Frequently Asked Questions about Accessory Dwelling Units (ADUs)

Is my property eligible to add ADU?
Most likely yes. ADUs are legal to build on all properties that allow residential uses.
How large does my property need to be for me to construct an ADU?
There is no minimum lot size
How tall can an ADU be?
Recent changes to State law have increased the maximum height allowances for ADUs. ADUs attached to the primary dwelling are allowed to be up to two stories or the height of the primary dwelling, whichever is lower. Detached ADUs within ½ mile walking distance of a high-quality transit stop are allowed to be up to 18 feet in height, plus an additional two feet to align the roof pitch with that of the primary dwelling. On lots that allow multifamily residential uses, an ADU height allowance is provided of 18 feet, regardless of proximity to transit. All ADUs not covered by one of the previous three exemption categories above are allowed to be up to 16 feet in height, which is generally considered insufficient to allow for two-story ADUs.

What's the difference between an ADU and a JADU?
A Junior ADU (JADU) is converted within the walls of the primary home or attached garage; is up to 500 square feet in size; must contain an efficiency kitchen with appliances, a food preparation counter, and storage cabinet; and may include its bathroom, or share one with the main residence. Any accessory residence not classifiedas a JADU is an ADU. For JADUs, the homeowner must occupy either the primary home or the JADU; however, for ADUs, both the primary home and an ADU can be rented simultaneously. 
Can I convert the second story of my existing home to an ADU?
Yes. ADUs may be converted out of space on the second floor of an existing home, though a
separate exterior entrance will need to be provided. 
How many ADUs can I build on my property?
Only one ADU and one JADU can be constructed on a property developed, or proposed to be developed, with a single-family home. On properties with multi-family developments, up to two detached ADUs are allowed; or one or more converted ADUs may be constructed within portions of existing multiple-family dwelling structures that are not used as livable space, totaling up to 25% of the existing multiple-family dwelling units on the lot. For example, if a building has 40 apartments, the owner could build 10 total ADU conversions. 
Can I add an attached covered patio or garage to my ADU?
Yes. Attached covered patios or attached garages are not considered living area, and do not count towards the size restrictions for interior living space within ADUs. 
Do I need to provide parking for an ADU?
One parking space is required for new ADUs. However, no parking is required if the property is located within ½ mile walking distance from a public transit stop, or for conversions of existing space, such as a garage to an ADU. 
Do I need to replace existing parking when demolishing or converting an existing garage, carport, or covered parking structure to an ADU?
No. When a garage, carport, or covered parking structure is demolished for the construction of an ADU or converted to an ADU, the off-street parking spaces are not required to be replaced. 
How large can an ADU be?
The maximum size of an ADU with 2 or more bedrooms is 1,200 sf, or 850 sf for a 1-bedroom or smaller ADU. There is no limit on the number of bedrooms within an ADU. In addition, the converted ADU created within an existing structure may be expanded up to 150 square feet for ingress and egress purposes. 
Can I build an ADU for use as a short term rental?
No. Under State law, new ADUs or JADUs may not be rented for a period of less than 30 days. 
Will my property taxes go up if I build an ADU?
Yes, but only for the ADU, not for your existing home. The applicable property tax rate is levied based on the cost to construct the ADU; the resulting amount is added to the tax bill for the existing home on the property. The cost to construct the ADU is calculated by the county tax assessor based on the size of the ADU, multiplied by a cost per square foot factor used for ADUs.  
Internal conversions may be classified as either an ADU or a Junior ADU (JADU). When does it make sense to apply for one or the other?
JADUs require a deed restriction to be filed on the title of the property, limiting them to owner-occupation of either the JADU or the primary home into perpetuity. On the other hand, classifying the project as a JADU would keep the option open to build an ADU later. JADUs can usually be built slightly more affordably than ADUs because separate utility shut-offs are not needed for plumbing or gas, or a separate sub-panel for electricity, and they can share the water heater and HVAC system with the main house. The savings can sometimes be significant and can be the reason people opt to build them. There are pros and cons to JADUs and good reasons for people to either classify their unit as a JADU or an ADU.  
Are Davis-Bacon / prevailing wage laws triggered for applicants seeking to use pre-approved plans developed as a part of this project?
When a new dwelling unit is seeking approval, are new ADUs allowed to be approved at the same time?
Yes, a property owner building either a new single-family or multifamily structure can also submit plans to build an ADU at the same time.