In California, no matter which jurisdiction you are in, a detached ADU can be built up to 800sq feet. As long as they are less than 16 feet high and have a 4 foot rear and side yard setbacks.
Due to their rise in popularity, one of the main changes for the 2020 California’s ADU rules is that it is easier to legalize unpermitted ADUs. You can now bring your unpermitted ADU up to code within 5 years. Another change is a shorter approval period. Before 2020, the approval period for ADUs was 120 days, but now California cities must provide ministerial approval or denial within 60 days of receiving the application.
Also, neither HOAs nor Covenants, Conditions, and Restriction can reasonably prohibit the development of ADUs. Californian homeowners are now allowed to add 2 ADUs on a single-family zoned property. According to the California law change, one must be a full ADU and the other a JADU, which can be created by converting a part of the existing residence (cannot be larger than 500 square feet). Both the ADU and JADU may be rented but not sold separately from the primary residence. There has also been a change in impact fees.
In accordance with the 2020 rule changes, cities in California can no longer charge impact fees for ADUs that are under 750 sq. ft. On the other hand, if you have a garage that you want to convert but find it easier to replace, the 2020 rule changes permit you to remove it and replace it with a new ADU that matches its footprint to maintain the existing reduced setback.
