Accessory dwelling units
ADU guides for San Diego County
A garage conversion in California is an accessory dwelling unit project, and the rules that decide what you can build are state law, not local opinion. These are the answers that change what your project looks like, each one quoted from the statute it comes from.
Homeowners call the result a granny flat, a casita, an in-law unit, or a backyard cottage. The code calls it an ADU, or a junior ADU when it sits inside the house.
What Is an ADU ADU stands for accessory dwelling unit: a second, self-contained home on a lot that already has a house. Read the rules Detached vs Attached ADU Whether your garage is attached to the house or standing on its own changes which unit you can legally build, not just how the job is priced. Read the rules ADU Parking Requirements The most common worry about converting a garage is losing the parking space, and on this point state law is unusually direct: a city cannot make you replace it. Read the rules ADU Size and Height Limits A garage conversion sits in a favourable corner of the size rules: converting existing space is not held to the square-footage cap that applies to a newly built ADU, which is why a large two-car garage can become a bigger unit than you might expect.. Read the rules ADU Permit Timeline State law puts a clock on your city, and it is shorter than most homeowners expect. Read the rules ADU Fees and Impact Fees There is a real fee break in state law for smaller units, and it is narrower than the way it usually gets repeated. Read the rules ADU Fire Sprinkler Rules One of the more expensive fears about adding an ADU is being told the whole house now needs fire sprinklers. Read the rules Prefab ADUs and ADU Kits Prefabricated and kit ADUs are marketed on speed, and the single most useful thing to know before you shop is that they do not shorten or skip the permit. Read the rules ADU Floor Plans and Layouts What will actually fit is a question about your garage, not about a plan book. Read the rules
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