A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateADU Company in Fontana, CA
Building an ADU in Fontana runs most homeowners between $180,000 and $350,000, depending on whether you go prefab or site-built, and most jobs take 9 to 14 months from first conversation to final inspection. What makes Fontana different from other Inland Empire cities comes down to three things: hot, dry summers that punish cheap materials, a housing stock that leans older ranch-style and benefits from thoughtful additions, and city permit requirements that catch out contractors who do not file here regularly. We are Benson ADU Builders, and we put every Fontana price in writing before work starts. Call (903) 568-7222 for a free estimate.
Why Fontana Homes Are Different
Fontana sits at the base of the San Gabriel Mountains, where summer temperatures routinely cross 100°F and the wind picks up in the fall. That combination means an ADU’s roof, insulation, and cladding do real work here. We spec James Hardie cladding on most exterior walls because it stands up to Fontana’s UV exposure and the fine dust that blows through the foothill neighborhoods. A poorly insulated ADU in Fontana is not just uncomfortable in August; it runs cooling bills that eat into the rental income most owners are counting on.
Fontana’s existing homes are largely single-story ranches built from the 1950s through the 1980s, concentrated in neighborhoods like Southridge, Heritage, and along Sierra Avenue. Those lots tend to be larger than what you would find closer to the coast, which is good news for an ADU: setback requirements, the minimum distance your structure must sit from property lines, are easier to satisfy on a wide, deep lot. That said, many older Fontana lots have undocumented easements and older utility lines that need locating before any foundation work. We pull permits for every Fontana project, and we do not start digging until the underground is mapped.
Fontana requires ADU and home addition plans to pass the same plan-check process as full home construction, including square footage limits and parking provisions. Some HOAs in newer master-planned communities, particularly in northern Fontana near Summit Heights, have their own review process layered on top. A contractor who does not account for that dual approval can hand you a schedule that slips a month before you have even broken ground. We factor HOA review into the written timeline from day one.
Our Main Fontana Services
Most Fontana homeowners call us about two things: adding an ADU for family or rental income, and expanding the footprint of the house itself. Here is what each looks like locally.
ADU Builders in Fontana
We build detached ADUs, garage conversions, and JADUs, which are junior units carved from existing square footage. On a typical Fontana lot, a detached ADU between 400 and 800 square feet gives you the strongest rental upside, and a prefab route through a brand like ADU Builders in Fontana can cut months off the construction timeline compared to a fully site-built structure. Prefab panels arrive on a truck, not as a pile of raw lumber, so the weather risk to your project drops significantly. We help you decide between prefab and site-built based on your lot access, your target rent, and your budget, then put the choice in writing.
Home Addition Contractor in Fontana
A home addition in Fontana typically means pushing a wall out to gain a family room, a primary suite, or a larger kitchen, or enveloping an existing patio. We work with your home’s current roofline and foundation rather than fighting it. On older Fontana ranches, that often means matching slab-on-grade foundations, and our Home Addition Contractor in Fontana crews have handled enough of those to know exactly what a 1960s slab can and cannot carry. We also flag the practical stuff early: where the HVAC is, how far the panel is from the new load, and whether the addition triggers a re-roof requirement under Fontana code.
Room Addition Contractor in Fontana
A room addition is smaller than a full addition: one bedroom, a home office, a bonus room over a garage. On a Fontana ranch, room additions often fit cleanly onto the back of the house, which keeps the street-facing appearance intact and avoids a lot of the aesthetic pushback that full additions can raise. You can view the scope of our Room Addition Contractor in Fontana work before we start: we price per square foot, we confirm the exact placement, and we do not bill a change order unless you sign for it first. For a Fontana homeowner adding a bedroom for an aging parent or setting up a home office, this is often the most cost-efficient way to add square footage.
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.
Brands We Service in Fontana
We build with and service prefab ADU systems from Abodu, Cover, Dvele, Mighty Buildings, and Boxabl, plus Tuff Shed structures and James Hardie cladding. Here is where we diverge from a manufacturer-direct model: if you already own a prefab unit and want it finished, permitted, or repaired, we are the crew that shows up for it. Explore the full list on our brands page.
Pricing for ADU Company in Fontana, CA
| Service | Typical range in Fontana |
|---|---|
| Pre-fab ADU (one-bedroom) | $180,000 – $280,000 |
| Pre-fab ADU (two-bedroom) | $250,000 – $350,000 |
| Site-built ADU (one-bedroom) | $230,000 – $330,000 |
| Site-built ADU (two-bedroom) | $290,000 – $420,000 |
| Garage conversion to ADU | $120,000 – $200,000 |
| Convert existing finished space to JADU | $80,000 – $140,000 |
| Dual ADU + JADU (new + junior unit) | $280,000 – $430,000 |
| Detached single-car garage ADU | $150,000 – $250,000 |
| Permit and design package only | $15,000 – $30,000 |
| Kitchen home addition | $120,000 – $220,000 |
| Primary suite home addition | $130,000 – $240,000 |
| Home office room addition | $70,000 – $120,000 |
Three things push price up in Fontana: a second story, steep front setback variances on hillside lots, and upgrades to the home’s existing electrical panel, which older ranches often need before any meaningful square footage can be added. We write the full price before you sign anything, and that price is the price. No change-order surprise after framing begins.
Neighborhoods We Serve in Fontana
We work across Fontana, from the older ranch pockets south of Foothill Boulevard to the newer planned communities north of the 210. Every neighborhood has its own lot geometry and HOA reality, so we bid each project by address, not by zip code. Representative neighborhoods include:
- Southridge
- Heritage
- Summit Heights
- Northgate
- The neighborhoods along Sierra Avenue and Foothill Boulevard
Most Fontana project sites are reachable by our crews within a standard local service window, and we coordinate material drop-offs ahead of each phase so you do not end up with a flatbed blocking your driveway for a week.
Service Area – Cities Near Fontana
Our Fontana crews also cover the surrounding Inland Empire communities, including Bloomington, CA, Rialto, CA, Rancho Cucamonga, CA, and Riverside, CA. Scheduling and dispatch run through the brand’s Inland Empire office, and we coordinate each city’s permit requirements directly with the local building department.
Serving Fontana, CA - Our Local Coverage Area
We’re based in the Fontana 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 ADU Company in Fontana
A one-bedroom ADU in Fontana realistically sits between $180,000 and $330,000, with prefab falling toward the lower end and site-built toward the upper. The biggest variables are the lot’s access for an ADU unit, your existing electrical service, and whether the project adds a second story or retains a single level. That is why we walk every Fontana lot before we give a number, then we put that number in writing. Call (903) 568-7222 for a quote specific to your address.
Yes. Fontana requires full plan review and permits for both ADUs and garage conversions, and a JADU also requires a permit, even though it uses existing square footage. Skipping permits is not a shortcut; it is a liability when you sell the home or when an inspector finds the unpermitted work. We pull the permits ourselves and keep the inspection schedule on the calendar from framing through final. Call (903) 568-7222 and our Fontana project team can walk you through what your specific property requires.
We can and routinely do. Some Fontana HOAs, particularly in newer subdivisions north of the 210, require architectural committee approval before the city will process your permit. We prepare the HOA package, submit it under your name, and track both the HOA approval and the city plan check in parallel so the two processes do not stack and cost you weeks.
When you are ready to price your Fontana ADU, addition, or room addition, call us at (903) 568-7222. We answer in person, we price in writing, and we stand behind the work for a full 365 days.
What happens when you call
- 1A real person answersNo phone trees - talk to a local adu pro.
- 2You get an upfront price rangeHonest numbers before anyone is dispatched. No surprises.
- 3We come out and measureLicensed & insured, at a time that suits you - the visit and the quote are both free.
- 4You get the price in writingLine-itemed, yours to keep, and nothing starts until you say go.
What Fontana Customers Say
"Booked a consult online and met the project manager two days later. Weekly progress updates arrived by text with photos. ADU finished on schedule."
- Hannah W."Clean, quiet crew. They respected the neighbors, kept noise to working hours, and swept the driveway every evening."
- Hope C."Communication was the best part. I always knew what was happening that week without having to ask."
- Dolly N.
