Kitchen remodeling
Bathroom remodeling
Home additions & ADU
Roofing
Windows & doors
Driveway & pavers
FenceFree written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
Fast, Reliable General Contractor Across Ontario
Most Ontario homeowners planning a real renovation, an addition, a detached shop, or an ADU are not looking for a single-trade specialist. They are looking for one contractor who can hold the whole job together, from the foundation to the roof deck to the hardscape. That is what our General Contractor team does. We work across Ontario’s 91762, 91764, 91798, and 91758 zip codes, and we know the difference between a tract home on a 6,000-square-foot lot and a half-acre property off East Philadelphia Street. Call (866) 925-0334 to talk through your project before you sign anything.
Key Takeaways
- A home addition in Ontario typically runs $45,000-$130,000 depending on county permits, soils conditions, and haul distance.
- ADU construction on Ontario acreage is priced between $90,000 and $220,000, not the smaller city-lot figures you may see quoted for Pomona or Claremont.
- Ontario’s warehouse belt sits on former citrus grove land, which means old irrigation lines and disturbed fill are real risks that change scope and price.
- We write every allowance, setback, and grading plan into the contract before the first draw, so the price does not quietly drift after demolition.
Why Millwright Builders Is Ontario’s Preferred General Contractor Company
Our reputation in Ontario comes from walking the lot before quoting it. Noel Castañeda runs Millwright Builders with a simple rule: the first visit to a property is for measuring, checking setbacks, and looking at what is under the ground, not for writing a number on a business card. That discipline matters here because Ontario splits between the older citrus-and-dairy streets of 91762 and 91764 and the industrial warehouse ring along 91761. A contractor who only quotes city-lot remodels will miss what acreage work actually requires.
We have handled projects near Ontario International Airport, up toward the 10, and south toward the 60 where the warehouse tilt-ups meet old ranch lots. Homeowners in those areas tell us the same thing: they want one accountable builder, not a rotating cast of subs. That is exactly how we operate. One contract, one schedule, one person you can call when something changes.
Styles & brands we work with
Remodeling Contractor in Ontario
A Remodeling Contractor in Ontario handles renovations that go beyond paint and fixtures. If you are opening walls between 1950s ranch rooms, replacing a flat roof on a 91762 stucco tract house, or converting a garage into a rental unit, you need someone who understands how postwar Inland Empire homes were built. These houses have slab-on-grade foundations, low-slope roofs, and plumbing that is often a mix of galvanized steel and early copper. The work requires sequencing: framing before rough-in, rough-in before drywall, and a material schedule that does not stall in Ontario’s summer heat.
A kitchen remodel in Ontario runs $14,000-$45,000, with smaller kitchens at $9,000-$20,000. Bathroom remodels range from $9,000 to $28,000, and a room addition on a typical Ontario lot starts around $45,000 and can reach $130,000 when county permits, septic considerations, and grading are in play. These are real numbers from the local market, not national averages.
Whole-Home and Structural Work
When a remodel touches load-bearing walls, roofing, or the building envelope, the scope changes. Ontario’s Santa Ana winds punish poorly flashed roofs and siding, and the inland heat means cool roofing and reflective membranes are not optional upgrades. We specify materials to the climate, not to a generic Southern California default.
Renovations That Add Value Here
Ontario’s rental market near the 60 and I-15 corridors has made garage conversions and ADUs particularly attractive. A garage conversion in Ontario costs $30,000-$80,000, and a full ADU construction runs $90,000-$220,000. The range is wide because acreage properties often need new utility runs, septic upgrades, and additional grading.
Licensed General Contractor in Ontario
A Licensed General Contractor in Ontario is the difference between a project that passes inspection the first time and one that stalls behind a county stop-work order. In the 91761 warehouse belt, much of the residential work still falls under county jurisdiction, not city. That means septic setbacks, well clearances, and grading plans become line items in your contract. We pull the permits, schedule the inspections, and carry the accountability so you do not become an unpaid project manager.
Full general contracting licensure is the foundation. You should verify current license status before hiring anyone, but the point is that one license covers every trade on the job. When a roofer, an electrician, and a concrete crew are all on site, the person responsible for schedule and quality is us.
County Permits and Soils Reviews
Ontario’s agricultural history shows up in unexpected ways. Old citrus grove irrigation lines lie buried under disturbed fill on former grove land. When we scope a slab pour or a detached structure, we check for exactly that. A county soils review can trigger if compaction is suspect, and we would rather find that before the excavator does.
Grading, Drainage, and Open Lots
An open Ontario lot is not a blank canvas. Grade falls, drainage swales, and equipment access all change the cost of what looks like a simple structure. We set positive fall away from the house, plan for heavy vehicle access during the wet season, and write the drainage plan into the quote so you are not surprised later.
Trusted Brands We Service in Ontario
We specify brands based on how they perform in Ontario’s inland heat and wind, not because a showroom carries them. For roofing, we work with GAF and Owens Corning product lines, both established in the residential warranty market. For windows and doors that hold up to Santa Ana wind events, we source from manufacturers who back their products with real warranties. We also stock the fast-turn items our Ontario customers need most: common flashing profiles, sealants rated for high UV exposure, and concrete curing compounds suited to hot, dry pours. Every product we install, we have vetted, not just stocked.
See the difference
Before
After
Before
After
Before
AfterCommon General Contractor Problems We See in Ontario Homes
- Old citrus-grove irrigation lines under the fill. Ontario’s 91761 corridor was groves before it was warehouses. We have hit buried lines during routine grading, and the fix is a utilities locate and a change order, not a guess.
- Stucco and concrete failing from inland heat. Summer temperatures well above the coastal basin mean stucco cures too fast if the schedule ignores the forecast. Cracks appear weeks later. We write curing allowances into the schedule and the price.
- Flat and low-slope roofs on postwar tract homes. 91762 and 91764 hold thousands of 1950s-70s single-story homes with roof systems never designed for modern insulation demands. A roof replacement runs $8,000-$20,000 depending on deck condition and material choice.
- Quoting without walking the open lot. A phone-call estimate cannot see well setbacks, septic lines, or a drainage swale that needs re-grading. That is how scope-of-work blowups happen after the draw schedule is already set. We walk every Ontario property before quoting.
Pricing for General Contractor in Ontario, CA
Acreage work in Ontario costs more than the same square footage inside city limits. The reasons are specific: county permits, septic and well setback reviews, longer material hauls, equipment access, and soils surprises from former grove land. Here is what we actually quote in this market:
| Project | Typical Ontario Range |
|---|---|
| Home Addition | $45,000 – $130,000 |
| ADU Construction | $90,000 – $220,000 |
| Garage Conversion | $30,000 – $80,000 |
| Concrete Driveway Installation | $4,500 – $12,000 |
| Roof Replacement | $8,000 – $20,000 |
These ranges cover fixed-scope work with written allowances for the unknowns that are common here: fill compaction, irrigation line encounters, and grading corrections. Call (866) 925-0334 to schedule a free estimate. We walk the lot, check the setbacks, and put the numbers in writing before you commit to a draw schedule.
We Also Serve Cities Near Ontario
Our crews work across the Inland Empire’s western edge, from Montclair and Upland through San Antonio Heights and Claremont. If you are in Ontario or any of the surrounding communities, the same licensing, the same written-scope discipline, and the same walk-the-lot rule applies. Call (866) 925-0334 and we will set a time to see the property.
Serving Ontario, CA — Our Local Coverage Area
We’re based in the Ontario area and know this community well. Use the map below to see our service coverage — if you’re nearby, we can almost certainly help.
FAQs About General Contractor in Ontario
Building on acreage around Ontario typically costs more because county permits replace city permits, septic and well setbacks add review time and design constraints, material and equipment hauls are longer, and grading or drainage work is almost always required before construction starts. On a city lot in Pomona, none of those apply. Call (866) 925-0334 and we will walk your property to identify which of these factors actually affect your quote.
If a crew hits old citrus-grove irrigation lines or disturbed fill on your Ontario lot, expect a utilities locate, a compaction or soils review, and a written change order before work resumes. On a half-acre lot off East Philadelphia Street in 91762, our crew was scoping a detached shop and grading a drainage swale when the excavator cut through abandoned citrus-grove irrigation line buried below the fill. We reset the rough-in for the shop’s power and water, brought the pad to grade with a positive fall away from the house, and cleared inspection sign-off on the first pass. The key is having that risk written into the contract from the start. Call us before you sign with anyone else.
Yes, outbuildings, shops, and detached ADUs stay under the same contract as the main house. One general contractor, one schedule, one point of accountability. That matters on Ontario acreage because detached structures have their own setback, septic, and power requirements that interact with the main house. We sort all of it before the first draw.
We start every open Ontario lot with a grade check and a drainage plan. That means measuring the existing fall, identifying where water goes in a heavy winter rain, and setting positive grade away from any structure we build. If a swale needs re-cutting or fill needs compaction testing, that goes into the quote as a line item, not a surprise. Call (866) 925-0334 for a free lot evaluation.
In writing means fixed scope, written allowances, specific brand names, permit responsibilities, and a draw schedule tied to completed milestones, not to time passed. If you hit an old irrigation line or a failed compaction test, the change order is written and signed before work continues. You will never hear us quote a number over the phone and then pretend the job was bigger than we thought. Call (866) 925-0334 to schedule your free estimate and get your project scoped properly.
Written by Noel Castañeda, Owner at Millwright Builders, serving Ontario since day one.