ADUs & Additions in Ontario

City of Ontario Community Development, Building Department. Under the Development Code's residential standards, a pool, spa or pond 1.5 feet deep or more cannot be built in a front yard, must sit at least 3 feet from side and rear property lines and must be enclosed by a decorative nonclimbable fence or wall at least 5 feet high, while diving boards, slides, waterfalls and decorative rockscapes need at least 5 feet from side and rear lines. ADU applications go to the Building Department electronically through the city's Citizen Portal Access, and the city's ADU handout caps a detached unit at 850 square feet for a studio or one bedroom and 1,000 square feet for two or more, generally at 16 feet tall, with 4-foot side and rear setbacks and 6 feet of separation between detached structures. Exterior alterations to historic buildings, including homes in the city's eight designated historic districts, need a Certificate of Appropriateness reviewed by Planning staff, the Historic Preservation Subcommittee and the Historic Preservation Commission, or a Planning waiver for minor alterations. We prepare the drawings, make the submittal and handle plan-check corrections ourselves, so you are not the one chasing plan check.

Two eras share the city: the Chaffey brothers' original subdivision pattern, still intact around the historic downtown and Euclid Avenue, with early tracts such as College Park, subdivided into 48 lots in 1914, and Armsley Square, laid out in 1924, and Ontario Ranch to the south, where former dairy properties are being converted to master-planned neighborhoods. Development Code Table 6.01-1 sets the minimum traditional single-family lot at 18,000 square feet in the AR-2 district, 10,000 in RE-2 and RE-4, and 7,200 in LDR-5. One local condition that shapes the work: The Safety Element describes the alluvial sand beneath most of Ontario as very susceptible to erosion, with strong winds driving it onto property, and its policies require dust-control best management practices on all excavation and grading and prohibit excavation and grading during strong wind conditions as defined by the Building Code, which brings the wind forecast into any dig schedule.

All of it, including College Park, Armsley Square, Rosewood Court and El Morado Court. Our crews run every job out of our Cahuenga Pass base in Los Angeles, with our own people on site.

Detached ADU: generally $150,000 to $400,000+ across Southern California. What moves it is square footage, finish level, utility runs, and site access; garage conversions typically run well below a ground-up detached build. We give line-item pricing after seeing the site rather than quoting a number over the phone.

Plan a realistic year. Design and engineering typically take one to three months, city plan check and corrections add several more, and construction usually runs four to eight months depending on size and site access.

Usually yes, and often substantially, because the foundation, walls and roof already exist. The trade-offs are that you lose the garage, and older slabs and framing sometimes need upgrading to meet current code.

California ADU law is designed to allow long-term rental, and an ADU is one of the few ways to add rentable square footage to a single-family lot. Short-term rental rules vary by city, so confirm your local ordinance before counting on that income.

Yes. Plans, engineering, Title 24 and the city submittal are all handled in-house, including responding to plan-check corrections. That is a service we sell on its own, so it is not something we hand off.