ADU Builder in Cupertino

Size changes coverage, floor area, and fees

Cupertino’s accessory dwelling unit page (opens in a new tab) says ADUs of 800 square feet or less, measured as living area, are not limited by lot coverage, floor area ratio, or open space the way larger units are. ADUs over 800 square feet are limited by those standards. Units in multifamily developments are described separately.

The same page says ADUs under 750 square feet do not incur park, storm drain, or school impact fees, and larger ADUs still incur them. Confirm the current fee with Public Works and the school district. The page lists planning@cupertino.gov for zoning questions and building@cupertino.gov for the building permit. A building permit is required.

For a single-family property, the City’s FAQ on that page says a studio or one-bedroom ADU is limited to 850 square feet, and an ADU with two or more bedrooms is limited to 1,000 square feet. There is no separate bedroom-count cap beyond that size rule.

Junior ADUs, rentals, and what cannot be combined

The City says a single-family property can have a streamlined detached ADU of 800 square feet or less plus a junior ADU, for two units. A junior ADU cannot be combined with an attached ADU or with a detached ADU larger than 800 square feet. A junior ADU is created inside the principal home, not in a garage.

ADUs may be rented and may not be sold separately from the principal home. The City says ADUs, including junior ADUs, may not be used as short-term rentals. Junior ADUs also have an owner-occupancy rule and a recorded deed restriction. Read the current FAQ before you plan a rental.

Utility questions for a Cupertino ADU are collected on our Cupertino ADU utility planning guide. That guide does not replace the City’s standards.

Questions homeowners ask

Talk with R&B

R&B Master Construction Inc. · CSLB #1158657. Email info@rbmasterconstruction.com. Headquarters: 84 W Santa Clara St, Suite 700, San Jose, CA 95113. Hours: Monday–Sunday, 7:00 AM–5:00 PM Pacific Time.