A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateFast, Reliable ADU Builders Across Montclair
Most ADU projects in Montclair run $180,000 to $420,000 for a detached unit, while garage conversions typically land between $120,000 and $220,000 depending on what’s behind those 1950s walls. We’ve built enough of both across this city to know that the quote you get on day one is rarely the number that matters. The number that matters is the one after we open a wall and find what’s actually there. Call (831) 292-4191 and we’ll walk your lot, check your panel, and put a written price in your hands before you sign anything.
Montclair’s post-war tract homes are a specific animal. They were built fast, on slab, with 60-amp panels and single-car garages that were never meant to become living space. That’s not a problem if your builder knows what they’re looking at. It’s a five-figure surprise if they don’t.
Why Lodgewick ADU Riverside Is Montclair’s Preferred ADU Builders Company
We’re the ADU Builders team homeowners in Montclair call when they want the price in writing before a single nail goes in. Russ Delmar leads our crews, and he’s spent years working through what Montclair’s older homes throw at you: undersized framing, original slab foundations, and electrical panels that code says have to go the moment a wall comes down. We don’t flinch at any of it. We price it, we put it in the contract, and we show up when we say we will.
Every Montclair project runs under The Kingswell Guarantee. That means a written price before work begins, a defined arrival window, a clean job site every evening, and a written guarantee on the finished build. If something isn’t right within 365 days, we come back and make it right. Not a phone tag game. A scheduled return visit.
Our scheduling and dispatch run out of the Inland Empire office, which puts us close enough to get to any Montclair neighborhood quickly. Calls are answered by a live person, 24 hours a day. When you call about your project or your guarantee, you get a human. That shouldn’t be rare, but homeowners tell us it is.
ADU Construction in Montclair
ADU Construction in Montclair usually involves converting an attached garage, adding a detached unit in the back yard, or building a JADU (junior ADU) inside the existing home footprint. The work runs $120,000 to $420,000 depending on the route. What separates a smooth build from a nightmare here is what happens at the open-wall stage. Montclair’s pre-1960 homes often hide original wiring and framing that no amount of pre-bid optimism can fix. We plan for it before we start, not after the inspector shows up.
Garage Conversions on Original Slabs
Most attached garages in Montclair sit on the original slab, poured when the house went up. That slab wasn’t designed as a living floor. We check it for moisture, cracks, and level before we quote the conversion. If it needs sealing or leveling, that goes in the written price, not a change order later.
Permit and Code Upgrades
Opening a wall in an older Montclair home triggers code requirements that newer cities don’t hit as hard. We handle all permitting and pull the paperwork before work starts. Any upgrade the inspector flags gets priced, written up, and approved by you before we proceed.
Detached ADU in Montclair
Detached ADU builds in Montclair often mean a studio or one-bedroom unit in a back yard that measures 5,000 square feet or less. That’s tight, and it’s why setback rules matter more here than in Ontario or Upland. We check the city’s front setback requirements before we draw anything, so you don’t spend design fees on a plan the city will deny. A detached ADU in Montclair typically runs $220,000 to $420,000, finished and permitted.
Prefab and Panelized Options
For a faster path on a tight Montclair lot, we work with Abodu and Cover for prefab detached units. These arrive as engineered modules and get set on your prepared foundation. It’s a strong fit for back yards where a long stick-built construction timeline would mean months of disruption.
Studio and Junior ADUs
A studio ADU in Montclair runs $180,000 to $280,000. A JADU carved out of existing space inside the house can come in lower, often $80,000 to $150,000. Both need their own entrance and kitchenette to meet California ADU law.
Trusted Brands We Service in Montclair
We install and finish ADUs from Abodu, Cover, Dvele, and Mighty Buildings, and we match the brand to your lot and budget rather than pushing whatever’s on the truck. On Ramona Avenue, our crew opened a 1957 attached garage for a conversion and found undersized 2×4 rafters and original knob-and-tube wiring still live behind drywall. We priced a panel upgrade and reframing work order before touching the wall, and our lead gave the homeowner a written allowance update the same day the permit inspector flagged the wiring. That’s how it should go: the surprise gets priced, written, and approved. Not sprung on you at the end.
Common ADU Builders Problems We See in Montclair Homes
- Original 60-amp electrical panels that fail the open-wall inspection. Montclair’s pre-1960 tract homes often still carry the original 60-amp service. The city’s current code requires a 200-amp upgrade once walls are open, and a flat-price quote without an electrical allowance will bite you hard.
- Detached ADUs drawn for lots where setbacks don’t allow them. We’ve seen design fees spent on plans for a 5,000 sq ft lot that Montclair’s setback rules would never approve. We check setbacks before drawing anything.
- Moisture wicking through unsealed original slabs. Converting a mid-century attached garage without sealing the original concrete means the new living space pulls moisture up through the floor and fails final inspection. We seal and test first.
- Undersized rafters in 1950s garage framing. Garages built in the 1940s-1960s were meant to hold a car, not a ceiling. If the rafters are undersized, we reframe and price it before the work order gets signed.
Pricing for ADU Builders in Montclair, CA
Here are real numbers for Montclair’s market. A garage conversion runs $120,000 to $220,000. A detached studio ADU runs $180,000 to $280,000. A detached one-bedroom runs $250,000 to $420,000. A JADU inside the existing home runs $80,000 to $150,000. The biggest swing factor in Montclair is the electrical upgrade: if your home still has a 60-amp panel, budget an additional $7,000 to $12,000 for the service upgrade to 200 amps. We write every quote with line items and allowances, and you approve any change in writing before we proceed. Call (831) 292-4191 for your free estimate.
We Also Serve Cities Near Montclair
Our ADU Builders in Montclair crews also cover Ontario, Upland, Chino, and Mira Loma. If you’re just over the line, we’ll still show up, inspect, and write the price. The same guarantee applies.
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 Builders in Montclair
Usually yes. Most Montclair homes built before 1960 still have 60-amp panels, and city code requires 200-amp service once a wall is opened for living space. Budget $7,000 to $12,000 for the upgrade. We include an electrical allowance in every quote so it’s priced before you sign. Call (831) 292-4191 and we’ll check your panel in person.
Montclair enforces front setback requirements that can limit how far a converted garage’s entry can extend toward the street. We verify setbacks against your lot before we draw plans, so you don’t pay design costs on a project the city will deny.
It’s the point where the inspector looks inside your walls after we’ve opened them. What they find, like original knob-and-tube wiring or undersized rafters, must be brought up to current code before work continues. We handle that inspection and any resulting work orders in writing, with your approval first.
Sometimes, but not always. Original slabs were poured for garages, not living space. If the slab checks out structurally and we seal it against moisture, we can move forward. If it doesn’t, new footings go into the written scope before work starts.
We size mini-split systems to the ADU so you’re not forcing the original system to carry a load it was never built for. Montclair’s hot, dry summers and mild winters make efficient cooling and good insulation the difference between a comfortable unit and one you avoid from June through September.
Ready to see what’s behind your garage walls before you commit? Call (831) 292-4191 now for a free, written estimate. Russ Delmar and the Lodgewick team will walk your Montclair lot, check the panel, and put every number in writing before you sign.
Written by Russ Delmar, Owner at Lodgewick ADU Riverside, serving Montclair since 2010.
