ADUs & Additions in Chino Hills

City of Chino Hills Community Development Department, Building & Safety Division. Room addition and remodel plans start with the Building and Safety Division of the Community Development Department; once a submittal is complete it routes to both Building and Safety and Planning, a separate submittal goes to the Chino Valley Fire District, and the city puts plan review at generally 15 business days, longer for larger projects. On residentially zoned lots a pool or spa may not sit in the front setback and must stay at least five feet from rear and side property lines, measured from the water's edge for an in-ground pool, while mechanical equipment needs three feet and must be screened where visible from a right-of-way. New construction, ADUs included, and additions that enlarge a structure by 50 percent or more must keep ten feet of exterior wall separation from other structures unless built entirely of noncombustible materials, and must fit ember screens on attic vents and evaporative coolers. Inside the Fire Hazard Overlay District the same work must also meet Section 7A of the Building Code and keep thirty feet, clear to the sky, from structures on adjoining lots unless the Chino Valley Fire District and the Community Development Director approve an equivalent alternative. We prepare the drawings, make the submittal and handle plan-check corrections ourselves, so you are not the one chasing plan check.

Lots in Planned Development districts, Butterfield Ranch among them, follow the PD documents adopted for each project, while the base single-family R-S zone sets a 7,200 square foot minimum lot, Rural Residential 20,000 square feet and Agriculture-Ranch five acres, with larger minimums shown on the Zoning Map where terrain calls for them. The English Road area, designated Agriculture Ranch in the General Plan as large-lot land suitable for equestrian estates, sits in the Level 1 equestrian overlay, where horses and other large animals may be kept as an accessory use to the home. One local condition that shapes the work: CAL FIRE's local responsibility area map dated March 24, 2025 places much of the city's canyon and hillside terrain, Carbon Canyon included, in a Very High Fire Hazard Severity Zone, while parts of the north end map as nonwildland, so the zone is checked parcel by parcel.

All of it, including Los Serranos, Sleepy Hollow, Carbon Canyon and Butterfield Ranch. 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.