Permitting And The Streamlined Path.
Cupertino must respond to your ADU permit application within 60 days of submittal, and the full permitting process typically takes three to four months. Details live on the City of Cupertino ADU page.
The city also recognizes a special category it calls Streamlined Units, or 66323 Units: detached ADUs of 800 square feet or less, no taller than 18 feet, with 4-foot side and rear setbacks. These units are exempt from Cupertino's rule that ADUs match the main home's architecture, which removes a whole layer of design review. Abodu's backyard homes are purpose-built for exactly this pathway.
Size And Height Limits.
The minimum ADU size in Cupertino is 150 square feet. On single-family lots, detached ADUs can reach 850 square feet for a studio or one-bedroom, or 1,000 square feet with two or more bedrooms. On multifamily lots, detached units can go up to 1,200 square feet. All detached ADUs are capped at 18 feet tall.
Attached ADUs over 800 square feet cannot exceed half the primary home's floor area, with the same 850 and 1,000-square-foot bedroom-based caps, and a height limit of 25 feet or the main house's height, whichever is lower. JADUs top out at 500 square feet. Anything over 800 square feet also has to fit your zone's lot coverage, floor area ratio, and open space rules.
Setbacks, Design, And Parking.
Every Cupertino ADU needs at least 4 feet of setback from the rear and side property lines. Unless you use the streamlined pathway, your ADU must match the main residence's architectural style, including paint colors, building materials, and roof slopes.
Cupertino usually requires one off-street parking spot per ADU, but the requirement disappears if your property is within a half mile of a public transit stop or in a historic district. And if the ADU replaces an existing garage, no replacement parking is needed.
How Many Units Your Lot Allows.
ADUs are permitted on any Cupertino lot zoned residential or mixed-use, as long as there is an existing primary dwelling or one planned. On a single-family lot you can build one detached ADU up to 800 square feet plus one JADU; go bigger than 800 square feet and the JADU is off the table. Check what fits on your parcel with our free lot check.
Multifamily properties can host up to 8 detached ADUs, and existing non-residential spaces like offices or storage rooms can be converted into units, capped at 25 percent of the existing residential unit count. Abodu builds at that scale through our multifamily program.
What It Actually Costs.
Custom site-built ADUs in California routinely exceed $250,000 before the first change order lands. Abodu offers transparent published pricing: homes from $234,800 plus a published installation price, an expected all-in from $298,800 that covers design, permits, the factory build, delivery, and installation, with no surprises in between. See how the process works step by step.