Now that you're decided to push through your long-awaited ADU, you must learn all the stipulated rules and laws first before breaking ground. You may have allocated the right budget, found your top home remodeling builders, and imagined your ADU design, but have you ever thought of the actual space you'll consume when building one? If you're a property owner who's keen to know California ADU size limits and setbacks, here's a useful guide for you.
Let's say you're building a brand new ADU (separate structure from the main house) what are the requirements in terms of lot size coverage? A lot has changed with the new California rules in January 2021, if we're talking about previous laws, you may have a much-limited option since back then, ADU rules are much stricter. However, if we make such a decision now, you just have to be mindful of the four-foot setbacks. Ever since these changes have been made, there are certain rules about SB-881 that were adjusted as well—all lot coverage and floor area ratio requirements have been removed. As long as you meet those minimum setbacks, your ADU project is good to go.
It used to be that the ADU could only be a certain percentage of the size of the primary house. However, these new law changes have amended some of the ADU size requirements. The way that the regulations work is that if you have a detached ADU of up to 1,200 square feet and 16 feet high, your ADU has to be allowable if it meets within the setbacks but there might be other regulations that would apply for larger units. If the question would be, "is the main dwelling smaller than 1,200 square feet?" then yes, you'd be you'd still be allowed to have that 1,200 square foot ADU.
These AADU rules have been changing for several years now. First starting at the city level and in some cities and then the state getting on board and then it's just kind of never-ending progress. Basically, there were eight laws enacted that at the state level that impacts ADUs but the main overall concept is that if you fit within these four-foot setbacks and you're having a detached unit and you meet the size requirements—if you're within the structure, you're 800 feet or if you're a detached ADU, you're 1,200 feet in both cases 16 feet high—the city has to allow it. They can require that you go through a building submittal process and they can require that you go through a planning submitting process but they cannot outlaw these ADUs.
These new ADU rules have been a game-changer because in any location—even if you have a single-family home—you can have a JADU and an additional detached ADU outside of your unit. Basically, it's called the obliteration of single-family zoning in California because if you have a Victorian where you have an entire bottom floor of storage that most people don't use or a house that had a garage that was too small for a car because was it built in the 1930s, you convert that unit into a JADU then if you also have space in your backyard within these setbacks you can build another unit as long as they meet those size requirements.