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
Finding a General Contractor in Ontario who understands the difference between a 1970s tract home near Euclid Avenue and a new build at Ontario Ranch isn’t easy. The two require entirely different skill sets, different material specs, and different permitting paths. Square One Builders works both sides of that line. We’re a full-scope General Contractor team led by Brent Calloway, and we’ve been managing remodels, additions, and ADU projects across Ontario’s 91761, 91762, and 91764 zip codes for years. If you’re planning a kitchen remodel, a detached ADU, or a whole-home renovation, call us at (877) 688-9930 and we’ll give you a straight answer on scope and cost.
Why Square One Builders Is Ontario’s Preferred General Contractor Company
Ontario homeowners keep calling us for one reason: we don’t make them juggle three separate contractors for roofing, plumbing, and cabinetry. One contract covers every system. When we quote a kitchen remodel in Ontario, that quote includes the countertop fabrication, the plumbing rough-in, the window replacement, and the finish carpentry. Nothing gets handed off to a sub you’ve never met and can’t hold accountable. Brent Calloway built the company on that principle, and it’s why our Ontario clients stay with us for the next project.
Local knowledge matters more here than in most Inland Empire cities. Ontario sits at the junction of I-10 and I-15, and the construction market is split between fast-turnaround commercial work and volume residential builds on former agricultural land. That’s a different world from coastal LA. Our crews know which Ontario parcels fall under city jurisdiction and which ones sit in county territory, which changes everything about plan check, septic setbacks, and grading requirements. We’ve pulled permits in Ontario enough times to know where the delays hide.
Styles & brands we work with
Remodeling Contractor in Ontario
Hiring a Remodeling Contractor in Ontario means hiring someone who can walk into a 1960s ranch house off Grove Avenue, identify the load-bearing walls that were framed before modern shear-wall codes, and plan the remodel without triggering a full seismic retrofit you didn’t budget for. We’ve remodeled kitchens, bathrooms, and whole homes across Ontario’s older core, where cast-iron drain lines and 100-amp panels are the rule, not the exception. The scope of a remodeling job in Ontario typically runs $14,000 to $45,000 for a kitchen, $9,000 to $28,000 for a bathroom, and $45,000 to $130,000 for a home addition. Those are real numbers from real Ontario bids, not national averages.
Kitchen and Bath Remodels
A kitchen remodel in Ontario usually means reworking a galley layout in an older tract home or gutting a builder-grade kitchen in a 2000s house near Ontario Ranch. We spec the cabinets, counters, and fixtures from our brand portfolio, not whatever the local supplier happens to stock. For bathrooms, we’ve done everything from tub-to-shower conversions in Euclid-area bungalows to full primary-bath gut remodels in newer subdivisions.
Whole-Home and Addition Work
When an Ontario homeowner needs more square footage, the math usually points to an addition before a move. We scope additions from foundation to roof, including the Title 24 energy upgrades that Ontario’s hot summers make non-negotiable. Expansive clay soil under many Ontario lots means we soil-test before we pour, and we build the drainage plan into the quote from the start.
Licensed General Contractor in Ontario
Working with a Licensed General Contractor in Ontario protects you from the unpermitted-work headaches that plague resale in this market. Ontario home inspectors and appraisers are familiar with the city’s aging housing stock, and they flag unpermitted additions and converted garages regularly. We pull permits on every project, schedule the inspections, and stand behind the work. For a garage conversion in Ontario, expect to pay $30,000 to $80,000. An ADU construction project on an Ontario lot runs $90,000 to $220,000. Those ranges include the site work, utility connections, and county or city fees that flippers and unlicensed operators leave out of their bids.
ADU and Detached Structure Builds
Ontario Ranch and the south side sit on former dairy land, and that changes everything about building a detached ADU or shop. We’ve hit buried manure-impacted soils and old farm infrastructure that required over-excavation and clean-fill import before we could pour a slab. That’s not a surprise change order we spring on you mid-project. We soil-test first, scope the export and import costs, and put them in writing before you sign.
Permitting and Setbacks on Acreage
If your Ontario parcel falls under county jurisdiction rather than city of Ontario permitting, your ADU or addition has to meet septic and well setback requirements that city lots never face. We coordinate that from day one. On a half-acre lot off Grove Avenue in south Ontario, our crew hit a layer of dairy-era manure-impacted soil while grading for a detached ADU and shop. We over-excavated, imported clean fill, and built the septic and well setbacks into the scope before the first inspection. The clients also wanted a Kohler rough-in for a future outdoor bath, so we coordinated the underground plumbing with the county inspection sign-off before backfilling.
Trusted Brands We Service in Ontario
Ontario homeowners ask us about brands by name, and we’re authorized to source and install from a portfolio of 50+ manufacturers. For roofing, we install GAF, CertainTeed, and Owens Corning systems, so whether you want a standard architectural shingle or a reflective cool roof for Ontario’s hot summers, we spec the right product. For countertops, we offer Cambria and Silestone at different price tiers. For windows, PGT and Therma-Tru. We order direct and stage materials at our Westminster yard, which means Ontario projects don’t sit idle waiting on a supplier truck.
See the difference
Before
After
Before
After
Before
AfterCommon General Contractor Problems We See in Ontario Homes
- Dairy-land soil surprises on the south side. Ontario Ranch and areas south of the 60 were dairy and agricultural land for generations. Grading for a slab or driveway often uncovers manure-impacted soil that has to be over-excavated and exported, which adds real cost a flat-lot quote misses.
- Expansive clay under older slabs. The clay soil common across Ontario’s older neighborhoods expands and contracts with moisture, which stresses foundations and flatwork. We see cracked slabs and sticking doors in 1950s-70s tract homes near Euclid Avenue regularly.
- County vs. city permitting confusion. Parcels on Ontario’s edges or in unincorporated pockets fall under county jurisdiction, which changes setback rules, septic requirements, and plan-check timelines. Assuming city permitting when the parcel is county causes costly delays.
- Undersized electrical panels in mid-century homes. Ontario’s older housing stock was built for 60-amp or 100-amp service. Adding a kitchen remodel, an EV charger, or an ADU usually means a panel upgrade, and that has to be in the scope from day one.
Pricing for General Contractor in Ontario, CA
Here’s what full-scope work actually costs in Ontario, based on recent bids we’ve written for local projects:
| Project Type | Ontario Market Range |
|---|---|
| ADU Construction | $90,000 – $220,000 |
| Home Addition | $45,000 – $130,000 |
| Garage Conversion | $30,000 – $80,000 |
Three things move the number on an Ontario project more than anything else: soil conditions, permitting jurisdiction, and haul distances. A detached ADU on former dairy land with manure-impacted soil and a long equipment access path costs more than the same ADU on a clean, already-built city lot. We don’t quote you a flat lot price and then hand you a change order when the soil test comes back. We test first, scope the export and grading, and put every line item in the written estimate. Call (877) 688-9930 for your free estimate.
We Also Serve Cities Near Ontario
Square One Builders serves General Contractor in Ontario and the surrounding Inland Empire communities. We regularly run projects in Montclair, Upland, Chino, and San Antonio Heights, so if your property sits near the Ontario border or in an unincorporated pocket, we can still handle the full scope.
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
If your parcel is outside Ontario city limits and falls under San Bernardino County jurisdiction, you need a county permit, and county rules govern septic and well setbacks, lot coverage, and access requirements. We verify jurisdiction before we draw plans, so you don’t lose weeks to a plan check filed in the wrong office. Call (877) 688-9930 with your address and we’ll confirm which path applies.
We soil-test before we quote the grading, not after. If the test shows manure-impacted soil or buried farm infrastructure, we scope over-excavation and clean-fill import as a line item in the original estimate. That way the cost is on the table before you sign, not buried in a change order later.
Grading and soil work are usually the biggest swing factors on acreage. A flat city lot with clean fill might need minimal grading, while a south Ontario parcel with dairy-era soil, expansive clay, or poor drainage can require significant over-excavation, import, and compaction before any structure goes up. We scope that work upfront so the price you approve is the price you build for.
Yes, and we do it regularly on Ontario acreage lots. Combining the ADU, shop, and any future plumbing rough-ins under one permit set saves plan-check fees and avoids re-opening the site later. We coordinate the county or city inspections so the underground work gets signed off before backfill, and one team stays accountable for the whole scope. Call (877) 688-9930 to talk through your layout.
Allowances are dollar amounts we set aside in your budget for materials you’ll select later, like tile, countertops, or plumbing fixtures. On acreage projects, we build the allowance schedule at the same time we scope the site work, so you know exactly what’s covered and what’s a selection you’ll make during construction. We don’t pad allowances and we don’t hide low ones to win the bid.
Written by Brent Calloway, Owner at Square One Builders, serving Ontario since day one.