ADU Size and Setback Requirements - Another Frequently Asked Question
[update 11/3/2020] The HCD has updated its guidance around size and setback requirements in September 2020. the shortest answer to this topic is that if your local jurisdiction has no ordinance regulating ADUs, then you can build up to 1200 square feet, 16 feet high, with 4 foot side and rear yard setbacks - and there are no requirements based on Floor-Area-Ratios (FAR), lot coverage, open space, or minimum lot size. If your property is in a jurisdiction with its own ADU ordinances, the regulations can limit you to 850 sq ft (or 1000 sq ft if the ADU has 2+ bedrooms) and it can impose requirements based on Floor-Area Ratios (FAR), lot coverage, open space and minimum lot size. But there is a “statewide exemption ADU” where you can build an ADU up to 800 square feet, 16 feet high, and with 4 foot side and rear yard setbacks, and it should be exempt from the FAR, lot coverage, open space, and min lot size requirements. [/update]
If you're building an ADU in California, you need to know your rights. It used to be complicated, but a suite of laws that went into effect in January 2020 have simplified the requirements across the whole state. There are still lots of restrictions and places to get tripped up, but it’s much more straightforward and build-friendly than it was before!
ADU Setback and Size Restrictions USED to be complicated
In the past, many cities used restrictive ordinances to put complicated limits on the maximum and minimum size of your accessory dwelling unit. They could say that the accessory dwelling unit should not be greater than 50% of the primary house on the property, or they could require it be smaller than a certain percentage of the lot size.
But in January 2020, a number of new state laws kicked in that supersede these local ADU zoning ordinances. There are now very strict rules about what cities can require, which gives more freedom to homeowners thinking about building an ADU.
One such homeowner attended our How To ADU virtual webinar and asked us about those setback and maximum size rules.
Our expert guest Laura Blair from BuildZig talked about what restrictions she faces in Oakland and the east bay, and summarized some of the new accessory dwelling unit laws that cover setbacks, minimum/maximum unit size, and lot size requirements.
Who are these ADU experts?
Laura Blair is a member of the California Bar and the COO of BuildZig. She has significant expertise in a number of fields including land use (her legal specialization) as well as planning and permits (often referred to as entitlements).
BuildZig is a one-stop shop to get consumers from planning through construction to completed projects. And that makes them very good people to talk to for homeowners like How To ADU subscribers.
The webinar was very informative and we thought we’d share the video recording here for others to benefit.
What other ADU topics did we discuss?
Watch the whole Q&A ADU Webinar on our blog or by joining the How To ADU Facebook group.
Accessory Dwelling Unit topics - Timestamp in video
Laura Blair went over the ABC’s of ADU’s - 14:05
ADU costs - 28:30
What’s possible at $200/sq ft?
What drives costs up unexpectedly?
Are there any ways to make your costs more predictable?
What are the lot size requirements for detached ADUs? Is there a maximum percentage of your lot that can be covered? - 35:45
Minimum set backs and lot coverage requirements
Can the accessory unit be larger than the primary house?
What are the new rules starting in January 2020? - 37:50
My property has been in two different cities over time. Who do I talk to at the city? - 40:36
Have you noticed cities or counties leading the pack to make ADU construction easier? - 44:35
Can I do a garage conversion and add on to it - can I combine my garage easement and a new foundation for the add-on? - 49:20
What if your foundation is brick or appears to be brick? - 54:15
Lots of great questions. We’ll be breaking some of the most popular questions out into their own articles.
Please share this article and the recording with friends and family looking into building an Accessory Dwelling Unit.
Get more videos like this one and free invitations to future How To ADU webinars by subscribing to our emails with the form below, or by joining the How To ADU Facebook group.