A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateADU Company in Rialto, CA
ADU construction in Rialto means working with flat, sandy lots, hot summers, and homes that date mostly from the 1950s through the 1980s. You’re adding a second living space to a property that was never plumbed, wired, or graded for one, so the work is less about framing and more about getting utilities, drainage, and setbacks right the first time. Fielding ADU Builders handles that from permit drawings to final inspection, with a written price before anything starts. Call (361) 315-4177 to talk through your lot.
Why Rialto Homes Are Different
Rialto sits on alluvial soil that drains fast in some spots and holds water in others, which matters when you’re tying a new foundation to an existing slab or running new sewer laterals. Many of the older homes near downtown and along the northern stretch of Riverside Avenue still have original clay sewer lines, and some newer tracts east of the 15 have HOA rules that limit building height and exterior materials. The city requires a soils report for most attached additions, and detached ADUs over 500 square feet usually trigger a grading review. You’ll also run into the Rialto Municipal Code’s specific setback language for rear-yard structures: in many single-family zones, a detached ADU has to sit at least 4 feet off the rear and side property lines, unless the planning division grants a setback variance (written permission to build closer than the standard rule allows). On top of that, summers here routinely push past 100 degrees in July and August, so we schedule concrete pours in the early morning and stage materials to keep adhesives, sealants, and roofing products inside their rated temperature windows. A contractor who does not plan for Rialto’s heat and soil is the one who loses a week in August or pours a stem wall that settles.
Our Main Rialto Services
Most Rialto homeowners call us about one of two things: adding square footage to the existing house, or converting what they already have into rentable or livable space. Here is how each plays out in Rialto.
Room Addition Contractor in Rialto
Room additions in Rialto generally fall into two buckets: a master suite and bathroom bump-out on a 1960s or 1970s era ranch, or a family-room extension on a newer home that needs the roofline matched. Matching stucco texture and roof pitch on Rialto’s older tract homes takes care, and the city will want structural calculations for any new opening cut through an exterior wall. We handle the drawings, the permit set, and the build itself. Full details are on the Room Addition Contractor in Rialto page.
Garage Conversion Contractor in Rialto
Garage conversions are one of the most cost effective ways to add a bedroom or rental unit in Rialto, because the slab, roof, and framing already exist. The work moves into raising the floor to meet finished elevation, insulating the walls and slab edge, upgrading the electrical panel if it is still a 100 amp, and adding the required egress window. Rialto treats an attached garage conversion as living space, which means it counts toward your lot’s floor area ratio. See the full scope on the Garage Conversion Contractor in Rialto page.
ADU Builders in Rialto
A detached ADU in Rialto is a house, just a small one: its own foundation, its own service panel, its own water and sewer connection. That is the honest description. We build conventional stick-framed ADUs and we also work with prefab platforms like Cover and Dvele when the lot access is tight or a homeowner wants the build compressed into fewer on-site weeks. Either way, the unit has to pass Rialto’s building and fire inspections like any other dwelling. The ADU Builders in Rialto page covers floor plans, site prep, and what the city will ask for during plan check.
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 Rialto
We work with several prefab and modular platforms on Rialto projects, including Cover, Dvele, and Boxabl. For conventional builds, James Hardie siding and Tuff Shed-style structures are common requests. Parts and materials are staged locally, and most hardware runs take a single day. See our brands for the full list.
Pricing for ADU Company in Rialto, CA
| Service | Typical range in Rialto |
|---|---|
| Detached ADU (studio, 400 – 500 sq ft) | $180,000 – $245,000 |
| Detached ADU (1 bed / 1 bath, 500 – 700 sq ft) | $220,000 – $310,000 |
| Detached ADU (2 bed / 2 bath, 800 – 1,000 sq ft) | $280,000 – $390,000 |
| Garage conversion (finished living space) | $95,000 – $165,000 |
| Garage conversion with new electrical panel | $105,000 – $175,000 |
| Room addition (200 – 300 sq ft) | $70,000 – $115,000 |
| Room addition (400 – 600 sq ft) | $110,000 – $185,000 |
| Room addition with bathroom | $130,000 – $210,000 |
Two things push Rialto ADU prices up faster than anything else: poor soil requiring deeper footings or a compacted fill, and sewer lines that need to be sleeved or replaced. Both show up most often in the older neighborhoods west of Cedar Avenue and around North Rialto. Whatever the final number, you approve it in writing before work begins, and that number is the number on the final invoice.
Neighborhoods We Serve in Rialto
We cover all of Rialto, from the older streets near the Metrolink station to the newer tracts out by the 210 and north of Base Line. Crews are local, so a site visit rarely takes more than a day to schedule.
- North Rialto (north of Base Line)
- Las Colinas
- Downtown / Civic Center area
- East Rialto near the 15
- West Rialto near Cedar Avenue
Service Area – Cities Near Rialto
Fielding ADU Builders also works in the cities around Rialto, including Bloomington, CA, San Bernardino, CA, Fontana, CA, and Grand Terrace, CA. If you’re within the Inland Empire, we can typically schedule a site visit within a few days.
Serving Rialto, CA - Our Local Coverage Area
We’re based in the Rialto 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 Rialto
Scheduling a site visit in Rialto usually takes one to two business days. Once a project is under contract, the permit set and city plan check drive the start date more than our crew schedule does. Call (361) 315-4177 and we’ll give you a straight answer for your street.
In most cases, yes. Rialto’s building division asks for a soils report when a new foundation is being poured or an existing slab is taking on new structural load. We schedule that as part of the permit package, so you are not chasing it yourself. Call (361) 315-4177 for an estimate that includes it.
No. The price goes in writing before any work begins, using the measurements and conditions we confirmed during the site visit. If Rialto’s plan check requires something extra, we tell you the exact cost before proceeding, and you approve it in writing. Call (361) 315-4177 for a free estimate.
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 Rialto Customers Say
"Solid job. Cabinet delivery was a week behind but they worked around it."
- Ben G."Insulation, drywall, and finishes were all well done. Feels like part of the house."
- Pete O."Built a detached ADU behind our house. The builder is a veteran and runs the site like a platoon: schedule posted, crew on time, everything labeled. Finished within a few days of the date."
- Ken W.
