A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateADU Company in Montclair, CA
Montclair homeowners call us most often about accessory dwelling units, garage conversions, and home additions on post-war lots that weren’t designed for any of them. The city’s aging single-family homes from the 1940s through 1960s sit on compact parcels, which means a good ADU plan here has to work with a small lot, an original slab foundation, and a single-car garage that hasn’t moved in sixty years. We do that work under The Kingswell Guarantee: a written price before anything starts, a real arrival window, a clean job site, and a written guarantee on every build. Call (831) 292-4191 for a free estimate.
Why Montclair Homes Are Different
Montclair’s housing stock runs heavily toward mid-century tract homes built fast and close together. That creates two realities for ADU work. First, most original garages are single-car and attached, which pushes many Montclair homeowners toward garage conversions as the most practical path to an ADU. Second, the original slab foundations were poured for lighter post-war construction, so before any conversion or addition we check what’s actually under the floor and plan footings accordingly. The city’s newer ADU ordinance has streamlined approvals compared to neighboring Ontario and Pomona, and that’s made Montclair a noticeably more active ADU market in the last few years. Hot, dry summers mean every plan we prepare for Montclair includes real attention to insulation and cooling, because an ADU that bakes in July isn’t a livable room, it’s a storage unit. Shaded side yards and existing mature trees change natural light and heat gain enough that we walk every lot before we write a proposal.
Our Main Montclair Services
The three services Montclair homeowners ask us about most are home additions, garage conversions, and ADU builds. Each has its own dedicated Montclair page linked below.
Home Addition Contractor in Montclair
Home additions in Montclair mean adding square footage to a post-war tract home, and the biggest question is usually how the addition ties into the original slab. We plan the roofline and foundation connection first, because a bad transition shows up as cracks and leaks within a year. Many Montclair additions become a primary suite or an expanded kitchen, and the city’s compact lots mean the design usually grows up or extends back rather than out to the side. Russ Delmar has been leading these builds under The Kingswell Guarantee since 2010. You can find full detail on Home Addition Contractor in Montclair.
Garage Conversion Contractor in Montclair
Most Montclair garage conversions take an original attached single-car garage and turn it into a studio, an office, or a private guest room. The original slab often slopes toward the driveway for drainage, so we level and insulate before anything else. Montclair’s ADU ordinance has made these conversions faster to permit than they were a few years ago, and because most lots leave no room for a detached unit, the garage is usually the most affordable path to a legal rental or family suite. The full scope is on Garage Conversion Contractor in Montclair.
ADU Builders in Montclair
Accessory dwelling units in Montclair range from garage conversions to detached backyard builds, though the tight lots make the garage route far more common. Russ Delmar and the team work with prefab manufacturers like Cover and Boxabl when the lot allows, and stick-frame builds when it doesn’t. Every ADU we build in Montclair goes through the same written-price-first process, and every project carries the 365-Day Done Right Promise in writing. For a full walkthrough of ADU options, timelines, and pricing, see ADU Builders in Montclair.
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 Montclair
We work directly with leading ADU systems including Cover, Dvele, and Mighty Buildings, and we handle warranty and service calls on those brands for Montclair homeowners. If your build uses a prefab system we know, parts ordering moves faster because we know the manufacturer channels. See our brands for the full list we service.
Pricing for ADU Company in Montclair, CA
| Service | Typical range in Montclair |
|---|---|
| Detached ADU (full build) | $180,000 – $320,000 |
| Attached ADU (conversion of existing space) | $120,000 – $220,000 |
| Garage conversion to ADU | $90,000 – $150,000 |
| Prefab ADU (installed, site work included) | $140,000 – $260,000 |
| Home addition (primary suite) | $110,000 – $190,000 |
| Home addition (kitchen expansion) | $70,000 – $130,000 |
| Foundation work for ADU | $8,000 – $25,000 |
| Utility hookups (sewer, water, electric) for ADU | $10,000 – $30,000 |
What pushes a Montclair price up: an original slab that needs leveling or reinforcement, an older electrical panel that can’t handle a second living unit, or drainage work on a flat lot with nowhere for water to go. What doesn’t push the price up is a change order at the door, because we give you the written price before any work starts and we hold to it.
Neighborhoods We Serve in Montclair
We work across the whole city, including the older tract neighborhoods north of the 10 and the streets closer to the Pomona border. Most of our Montclair work is concentrated in the mid-century subdivision streets where the original garages and slab homes were built in the 1940s and 1950s. We schedule estimates across the area within a few business days.
- North Montclair tract neighborhoods
- Streets east of Monte Vista Avenue
- Neighborhoods near Montclair High School
- Areas near Montclair Place shopping district
- South Montclair streets toward the Pomona line
Service Area – Cities Near Montclair
We serve Montclair and the surrounding Inland Empire communities, with scheduling coordinated from our Riverside-San Bernardino office. Homeowners in Ontario, CA, Upland, CA, Chino, CA, and Mira Loma, CA can call the same number for a free estimate.
Serving Montclair, CA - Our Local Coverage Area
We’re based in the Montclair 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 Montclair
Montclair’s updated ADU ordinance has shortened approvals compared to neighboring cities, but you should still plan for several weeks of plan review before construction starts. We handle the permit drawings and city submittal, and we give you a written timeline with your written price. Call (831) 292-4191 for a realistic schedule for your specific lot.
Not always. Many original Montclair garage slabs are thick enough for living space once we level and insulate them, but some have cracks or slope issues that need correction. We check the slab before we quote, so the number in your written price is the number you build with. Call (831) 292-4191 to schedule a free estimate.
Yes, we serve the entire city, from the tract homes north of the 10 down to the streets near the Pomona border. Our scheduling is coordinated from the Inland Empire office, and crews work locally in Montclair throughout the week. Call (831) 292-4191 to put your address on the schedule.
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 Montclair Customers Say
"A whole backyard ADU from scratch. Terrified me going in, but they kept me updated weekly and there were no nasty surprises. Quality work and a fair price."
- Noreen Fletcher"Detached unit in the backyard for rental income. They handled design and permits and gave me a real schedule. Came in close to on time and exactly on the written price."
- Benjamin Stahl"Added a suite for my dad. They walked us through every cost before a hammer swung and stuck to it. The written price is what we paid, no change orders."
- Ingrid Salazar
