General Contractor in Ontario, CA

Green Design and Build is a licensed general contractor (CSLB #1110975) based at 16120 Sherman Way in Van Nuys and working across western San Bernardino County, including Ontario, about an hour and a quarter east by the 10 or the 210 outside rush hour. We are a full-service residential general contractor and design-build remodeler for projects of every size — kitchens, bathrooms, ADUs, room additions, roofing, patio covers and whole-home renovations — serving homeowners across Los Angeles County, Orange County, Ventura County, western Riverside County and western San Bernardino County. Led by Dekel Sofer, we have completed hundreds of projects and hold a 4.7-star rating across 146 Yelp reviews.

Ontario is the largest city in the part of San Bernardino County we serve and the one with the widest spread of housing: a historic core of Craftsman and Spanish Revival homes along Euclid Avenue, post-war tracts between the 10 and the 60, and Ontario Ranch, the 13-square-mile master-planned community on the south side that the city expects to add roughly 50,000 homes by 2044. This page covers what that means for a residential project.

Ontario’s own permits

The city’s Building Department is at 303 East B Street, open Monday to Thursday 7:30 AM to 5:30 PM and Friday 8 AM to 5 PM, with the counter closed for staff meetings early on Tuesday mornings and the first Thursday of each month. Plan check questions go to (909) 395-2023 and inspectors to (909) 395-2362. Permits, plan check status and inspections run through the city’s online Permit Portal, and the department publishes a daily inspection schedule. We open the case, submit the set, clear corrections and schedule every inspection.

Three things shape Ontario projects more than the code itself:

• Historic preservation. Ontario runs a Historic Preservation Program that issues Certificates of Appropriateness for exterior changes to designated buildings and offers Mills Act contracts to owners who maintain them. The Euclid Avenue Historic District covers the avenue from G Street north to the 10, with 102 properties and 75 contributors built between 1888 and 1965. An addition, a new window pattern or a re-roof in a different material on a contributing house goes through that review before the building permit.
• HOAs in the new communities. Ontario Ranch neighborhoods and most tracts built since the 1990s have associations that review patio covers, additions, ADUs and exterior changes before the city issues a permit. Interior remodels generally need no approval.
• Heat. Ontario sits in Climate Zone 10, with summers well above 100°F, so cool roofs, low-E glass and attic insulation above code minimum are the upgrades that pay back fastest, and the state energy code requires a cool-rated product on any roof more than half replaced.

Electrical service changes go through Southern California Edison; water and sewer connections go through the Ontario Municipal Utilities Company, the city’s own utility.

Ontario housing stock, by area

North Ontario and the Euclid Avenue corridor (1888–1960s). The original Model Colony town: Craftsman bungalows, American Foursquares, Spanish and Mediterranean Revival, minimal traditional and early ranch homes on raised foundations along tree-lined streets. Galvanized plumbing, 60- or 100-amp panels, unbolted sill plates and single-pane wood windows are typical, and these are the Ontario homes where a whole-home renovation or a seismic bolting job makes the most difference.

Central and south Ontario between the 10 and the 60 (1950s–1980s). Single-story post-war and ranch tracts on slab foundations with attached garages, on lots large enough for a rear addition or a detached ADU; kitchen remodels, garage conversions and rear-yard ADUs are the common projects, and these are some of the most attainable single-family homes in the western Inland Empire.

Ontario Ranch (2010s–present). New two-story homes and townhomes on HOA lots south of the 60, delivered with bare backyards. Patio covers, pavers, pool surrounds and finished outdoor living are what owners ask for first, along with the occasional garage conversion once the family grows.

ADUs in Ontario

Ontario permits ADUs and junior ADUs under the state framework through its Building Department, with the rules in Chapter 5 of the Ontario Development Code. A junior ADU is limited to 500 square feet inside a single-family house, with an efficiency kitchen and either its own bathroom or a shared one. The city keeps a list of pre-approved detached ADU plans, approved within the current building-code cycle, that still need a submittal but get reduced staff review; under state law a permit for a pre-approved or previously approved plan must be decided within 30 days. Ontario’s larger post-war lots and the deep lots of the historic core are both good candidates for a detached unit, and a contributing house in the Euclid Avenue district adds a Certificate of Appropriateness for anything visible from the street. Our ADU rules calculator shows the state-law floor for your lot, and our guides on how much it costs to build an ADU and garage conversion cost explain the budget.

What we build in Ontario

• Kitchen remodeling — opening 1960s and 1970s kitchens to the family room; rebuilding Euclid Avenue-era kitchens with new plumbing and electrical behind period-appropriate cabinets. See our kitchen remodel cost guide.
• Bathroom remodeling — see how much a bathroom remodel costs.
• ADUs and garage conversions, using the city’s pre-approved plans where they fit.
• Room additions — rear additions on the post-war tracts; see our room addition cost guide.
• Whole-home renovations of the historic-core homes, with Certificate of Appropriateness review where it applies. See our remodeling services.
• Foundation and structural work — seismic bolting on raised foundations, slab repair on expansive soils. See warning signs your foundation needs repair.
• Roofing — cool-rated shingle and tile, and matching materials on historic homes; see our roof replacement cost guide.
• Patio covers, pavers and outdoor living — the first project in most Ontario Ranch backyards; see our patio cover cost guide.
• Concrete, retaining walls, artificial turf, fencing, outdoor kitchens and decks and landscaping and irrigation.
• Windows and doors with low-E glass, flooring and painting with coatings specified for sun exposure.
• Plumbing and electrical upgrades as part of remodels, performed by licensed tradespeople.

Permits in Ontario: how we run it

Historic review and HOA first, then the city. We check whether the house is a designated or contributing property, prepare the Certificate of Appropriateness or HOA architectural package where one applies, and submit it before the Permit Portal set so the two match. Plans, structural engineering and Title 24 energy compliance go in as one set; we clear corrections, pull the permit on East B Street and schedule inspections through to final. Our San Bernardino County page covers the rest of the western county — Rancho Cucamonga, Upland, Montclair, Chino, Chino Hills and Fontana — and explains where our service area ends.

Frequently asked questions

Can I build an ADU in Ontario?

Yes. Ontario permits detached and attached ADUs, garage conversions and junior ADUs of up to 500 square feet under California state law and Chapter 5 of the Ontario Development Code. The city keeps pre-approved detached ADU plans that get reduced review, and a permit for a pre-approved plan must be decided within 30 days under state law. Homes in the Euclid Avenue Historic District add a Certificate of Appropriateness for exterior changes.

Is my Ontario home in a historic district?

If it is on Euclid Avenue between G Street and the 10, it is in the Euclid Avenue Historic District, which has 102 properties, 75 of them contributors. Other designated homes exist across the older parts of the city. Exterior changes to a designated or contributing property go through the city’s Certificate of Appropriateness review before a building permit is issued; interior remodels do not.

Will my HOA need to approve my remodel?

In Ontario Ranch and most neighborhoods built since the 1990s, yes for anything visible from outside: patio covers, additions, ADUs, new windows and exterior colors. Interior kitchen and bathroom remodels generally need no HOA approval. We prepare the architectural package and submit it before the city set.

Who issues building permits in Ontario?

The City of Ontario Building Department at 303 East B Street, through its online Permit Portal. Plan check questions go to (909) 395-2023. Properties outside the city limits are permitted by San Bernardino County Building and Safety.

How far is Green Design and Build from Ontario?

About 55 miles, an hour and a quarter by the 10 or the 210 outside rush hour and closer to two hours in it. We group Inland Empire site visits into the same days, and once a project starts the crew assigned to it is on site every working day until it is finished.

Are you licensed to work in Ontario?

Yes. A California contractor’s licence is valid statewide, so CSLB #1110975 covers Ontario the same as Van Nuys. We are licensed, bonded and insured, and the licence and workers’ compensation can be verified on the CSLB site.

Ready to talk about your Ontario project?

Send us the address and what you want to build. We will tell you whether the house is in a historic district or an HOA, what the Permit Portal submittal needs, and what the schedule looks like. The site visit and the written estimate are free.