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
Hiring a General Contractor in Ontario means finding someone who understands what the Inland Empire actually does to a house. We work throughout the 91762, 91764, and 91761 zip codes, and we know the postwar tract stock, the Santa Ana wind damage, and the permitting path for ADUs on those big lots. Ken Stafford leads our team, and we answer the phone at (877) 752-4194 when you need a straight answer about scope, materials, or cost.
Most Ontario homeowners we talk to are not looking for a handyman. They are planning a kitchen remodel, a second-story addition, a garage conversion, or a full teardown-and-rebuild, and they want one contractor accountable for all of it. That is what we do. From the roofline to the kitchen counter, one contractor, one conversation.
Why Milpitas Construction Is Ontario’s Preferred General Contractor Company
Ontario is different from coastal LA and Orange County, and we treat it that way. The housing stock here is largely 1940s to 1970s single-story stucco on generous lots, with newer subdivisions pushing east toward the 15 and south toward the 60. Older tract homes in neighborhoods around Euclid Avenue and the historic downtown grid still have drywall-and-lath plaster walls, original galvanized plumbing, and shallow slab foundations. Additions and ADUs on those lots require tie-ins that inspectors flag when they are not done right, and we have done enough of them to know exactly what the City of Ontario plan checker wants to see.
Ken Stafford has built the company around single-contract accountability. When we run a whole-home remodel or an addition in Ontario, the roofing crew, the window crew, the paver crew, and the cabinet installers all answer to us. The homeowner gets one point of contact, one draw schedule, and one warranty conversation. That matters on a $45,000 addition or a $90,000 ADU, where finger-pointing between subs is the fastest way to a stalled job.
We also spec materials by name, so you know exactly what is going into your home. KraftMaid cabinets, Cambria countertops, Kohler fixtures, James Hardie siding, GAF roofing. Not “contractor grade” unknowns. Named brands with documented performance in this climate.
Styles & brands we work with
Hire a General Contractor in Ontario
When you hire a General Contractor in Ontario, you are hiring someone to own the entire build: permits, demo, framing, MEP rough-in, finishes, and final inspection. On Ontario’s postwar lots, that often means a room addition or a garage conversion that ties a new two-story structure into a 60-year-old slab and plaster wall assembly. A home addition in Ontario typically runs $45,000 to $130,000, and a garage conversion lands between $30,000 and $80,000 depending on whether you are adding a bathroom and a kitchenette.
Additions and ADUs on Postwar Lots
Ontario still has real lot size, which is rare in Southern California. That is why ADU construction is a current specialty for us, not a future offering. We work with modern prefab manufacturers like Abodu, Dvele, Mighty Buildings, Boxabl, and Plant Prefab, and we handle the site work, foundation, utility tie-ins, and final inspection. An ADU in Ontario runs $90,000 to $220,000.
Teardown-and-Rebuild Scope
Some Ontario homeowners skip the addition and go straight to a teardown-and-rebuild, especially on those old citrus-grove tract lots in the 91761 grid. We run that scope under one contract: demolition, site prep, new foundation, framing, roofing, windows, siding, interior finishes. The draw schedule matches what we actually do each phase, so you are never paying ahead of work.
General Contractor Services in Ontario
General Contractor Services in Ontario cover the full exterior-to-interior scope. We replace roofs on aging tract homes, install impact windows, rebuild kitchens and bathrooms, run paver driveways, and build fences that survive Santa Ana season. A roof replacement in Ontario runs $8,000 to $20,000, and impact window installation runs $8,000 to $25,000 depending on window count and frame material.
Exterior Envelope Work
Ontario’s inland heat and fall wind events punish exterior materials faster than most homeowners expect. We install GAF and CertainTeed roofing with hot-dip galvanized ring-shank nails and stainless ridge fasteners, not the coastal-spec hardware that lifts at the first Santa Ana. We also install PGT and ECO Window Systems impact windows that handle 100°F UV cycling without frame warping.
Interior Remodeling Scope
Inside the house, we run kitchens and bathrooms from demo to finish. A kitchen remodel in Ontario runs $14,000 to $45,000, a small kitchen $9,000 to $20,000, and a bathroom remodel $9,000 to $28,000. Countertops come from Cambria, Silestone, or Caesarstone. Cabinets from KraftMaid or Wellborn. Fixtures from Kohler or Grohe. You pick from proven contractor brands, not big-box leftovers.
What happens when you call
- 1
A real person answersNo phone trees — you reach a local pro.
- 2
You get an upfront price rangeHonest numbers before anyone is dispatched.
- 3
A background-checked tech heads outLicensed & insured, dispatched right away.
- 4
You approve before work beginsNothing starts until you say go.
Trusted Brands We Service in Ontario
We stock and install from a portfolio of 50+ brand-name product lines, and we keep the Ontario-relevant inventory moving. That means CWS and ECO Window Systems frames for the inland heat, James Hardie siding for fire resistance, and GAF roofing systems spec’d for wind uplift through the Cajon Pass corridor. For Ontario homeowners, we typically recommend ECO Window Systems or ES Windows on west-facing elevations where afternoon sun is brutal. Material selection is guided, not guesswork.
See the difference
Before
After
Before
After
Before
AfterCommon General Contractor Problems We See in Ontario Homes
- Santa Ana wind damage on ridges and patio covers. The first big fall wind event peels shingles at the ridge and lifts lightweight patio covers on older tract homes. We spec stainless ridge fasteners and fire-resistant cover assemblies from the start.
- Additions framed without slab and plaster tie-ins. A two-story addition on a 1950s slab needs proper shear wall connections and footing inspection. Inspectors in Ontario flag this constantly, and we build it right the first time.
- Cheap exterior hardware failing under UV cycling. Coastal-spec fasteners, thin-gauge railings, and unsealed paver joints corrode and crack within a few Ontario summers. We use hot-dip galvanized and stainless hardware and sealed paver joints.
- Flat or poorly graded roof drainage on older slabs. The first winter rains expose ponding water and site drainage problems on postwar lots. We regrade and tie new drainage into the existing slab before it becomes a structural problem.
Pricing for General Contractor in Ontario, CA
Here is what we tell Ontario homeowners when they ask about cost. Our pricing is honest and line-itemed, and we do not change the number once work starts unless you change the scope.
| Project | Typical Ontario Range |
|---|---|
| ADU Construction | $90,000 – $220,000 |
| Home Addition | $45,000 – $130,000 |
| Garage Conversion | $30,000 – $80,000 |
| Roof Replacement | $8,000 – $20,000 |
| Impact Window Installation | $8,000 – $25,000 |
The coastal-spec versus inland-spec gap is real. A cheap patio cover or roof fastener package may save $1,500 to $3,000 up front, but the first Santa Ana or the third 105°F summer will show the difference. We price the inland-spec version from the start, because replacing it later costs more. Call (877) 752-4194 for a free line-item estimate on your Ontario project.
We Also Serve Cities Near Ontario
We run crews throughout the Inland Valley, including Ontario and the surrounding communities. Homeowners in Montclair, Upland, Chino, and San Antonio Heights call us for the same full-scope work: additions, ADUs, roofing, windows, and whole-home remodels.
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
The coastal-spec version costs less because it uses lower-grade fasteners, thinner patio cover framing, and unsealed paver joints. In Ontario, the first Santa Ana event will lift shingles at the ridge, and three summers of 100°F UV cycling will warp and corrode the cheap hardware. Replacing it within a decade costs two to three times the original price gap. We spec inland-grade hardware from day one. Call (877) 752-4194 for a quote.
Yes. Garage conversions and ADUs in Ontario require building permits, and in most cases, a plan check through the City of Ontario. We pull permits, schedule inspections, and handle the entire approval path, including SB 9 lot-split and ADU compliance. Our draw schedule is tied to permitted milestones, so you are never paying for unpermitted work.
We start with a foundation inspection and a structural tie-in plan. The original 1950s slabs in Ontario are shallow and often unreinforced by modern standards, so we specify seismic anchors and shear wall connections that the plan checker will approve. We also match the new drywall to the old lath-and-plaster transitions so the addition does not crack at the seam.
A coastal-spec roof on a typical Ontario tract home might save $2,000 to $4,000 on fasteners and ridge hardware. An inland-spec roof with hot-dip galvanized ring-shank nails, stainless ridge fasteners, and GAF or CertainTeed shingles rated for wind uplift costs more up front but lasts through Santa Ana season without peeling. Windows are similar: PGT or ECO Window Systems frames rated for inland heat run $8,000 to $25,000, and the cheap vinyl alternative warps within a few summers.
We split the draw schedule into milestones: demolition and site prep, foundation and utility rough-in, framing and roofing, exterior envelope, interior rough-in, finishes, and final inspection. The ADU portion is drawn separately from the main house so you can see exactly what each phase costs. Ontario inspectors want to see that paperwork at sign-off, and we keep it clean from day one. Call (877) 752-4194 to walk through your scope.
Written by Ken Stafford, Owner at Milpitas Construction, serving Ontario and the Inland Empire since day one.