A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateFast, Reliable Home Addition Contractor Across Montclair
Adding a room to a Montclair home usually costs between $45,000 and $140,000 for a standard single-story addition, while a sunroom runs $28,000 to $65,000 depending on whether it’s conditioned space or a three-season room. Those numbers reflect what we see across Montclair’s post-war tract neighborhoods, where original slab foundations and aging electrical panels shape the scope more than square footage alone. We’re the Home Addition Contractor team that puts the price in writing before we touch a wall, and if something inside that wall isn’t right, we make it right under the 365-Day Done Right Promise. Call (831) 292-4191 to schedule a free estimate.
Why Lodgewick ADU Riverside Is Montclair’s Preferred Home Addition Contractor Company
Montclair homeowners keep calling us because we do what most contractors won’t: we tell you the truth about what’s behind the drywall before we start swinging hammers. The homes here were built between the 1940s and 1960s, and we know what that means. Knob-and-tube wiring. Undersized framing. Slabs that have settled in the valley heat. Our crews have opened enough walls along Ramona Avenue, Mills Avenue, and the neighborhoods west of Central Avenue to anticipate what code enforcement will require once the permit is pulled.
Every project runs under The Kingswell Guarantee, named for the family behind the company since 2010. You get a written price before work begins, a defined arrival window, a clean job site, and a written guarantee on every build. If something fails within 365 days, we come back and fix it free. Russ Delmar leads the Montclair team with a simple rule: say the price before the work, show up when we said we would, leave the place cleaner than we found it, and put the guarantee in writing. Our live person answers every call at (831) 292-4191, 24 hours a day, seven days a week. No voicemail, no chatbot, no runaround.
Sunroom Addition in Montclair
A sunroom addition in Montclair typically costs $28,000 to $65,000, and the biggest variable isn’t glass or framing – it’s whether the room gets tied into the home’s HVAC system or built as an unconditioned three-season space. Montclair’s hot, dry summers push a lot of homeowners toward insulated glass and a dedicated mini-split so the room stays usable from June through September. The inland valley heat means we spec higher R-value ceiling insulation and low-E glazing as standard, not upgrades.
Conditioned Versus Three-Season Design
When a sunroom is tied into the existing HVAC, the permit triggers current energy code requirements, which often means sealing the original exterior wall penetrations and adding insulation where the old wall used to be. On a 1950s ranch with original stucco, that’s straightforward work for our crew. The cost difference between conditioned and three-season typically runs $8,000 to $14,000 in Montclair, driven mostly by glazing packages and mechanical work.
Slab and Foundation Considerations
Montclair’s post-war homes sit on original slabs, and a sunroom addition means pouring new slab or footings tied to the existing one. If the original slab has settled – and we see this a lot in homes east of the 10 where irrigation overspray has been hitting the foundation line for decades – we level and repair before tying in new work. Written allowances in the contract cover this discovery so you’re not surprised by a change order at the door.
Room Addition Contractor in Montclair
A room addition contractor in Montclair is dealing with a specific housing stock: tract homes from the 1940s through 1960s, most on compact lots where the only practical direction to build is out, not up. A single-story room addition here typically runs $45,000 to $140,000, with the spread driven by whether the addition ties into the existing roofline, requires electrical service upgrades, or triggers foundation work. We’re the team that writes those numbers down before demolition starts.
Electrical and Code Upgrades
Here’s what actually happens when you open a wall on a Montclair ranch: you find knob-and-tube wiring still live, ungrounded circuits feeding modern appliances, and a 60-amp panel that city code won’t allow to serve an addition. The City of Montclair requires a dedicated circuit for new living space, and if the panel is undersized, a service upgrade to 100-amp or 200-amp becomes part of the job. We write an electrical allowance into every room addition contract so this upgrade is anticipated, priced, and approved in writing before we touch it.
Framing and Roof Tie-In
Adding a room to a mid-century home means matching the existing roofline, which on many Montclair homes is a low-slope comp shingle or original shake. The valley’s heat has baked a lot of these roofs, and we often find sheathing that needs replacement at the tie-in point. Our framing crews shim, level, and reinforce before tying into original trusses or rafters, and every tie-in gets a written scope review so you approve what’s actually needed, not what a contractor guesses.
Trusted Brands We Service in Montclair
We work hands-on with the ADU and addition materials that hold up in Montclair’s climate. For prefab ADUs and garage conversions, we install Abodu and Cover units, and for panelized and modular builds we run Dvele and James Hardie systems. James Hardie fiber cement siding is a common spec on Montclair additions because it resists the valley’s dry heat without warping like vinyl. We keep material lead times short and give Montclair customers a written schedule before work starts. When a homeowner on Benson Avenue needs a specific siding profile or a matching prefab floor plan, we spec it before the permit is filed.
Common Home Addition Contractor Problems We See in Montclair Homes
- Knob-and-tube and ungrounded wiring surfaces once walls are open. Most Montclair homes built before 1960 still have original wiring in sections, and an addition forces an electrical service upgrade that stalls the project if it wasn’t anticipated. We write the allowance into the contract so the upgrade is priced, not a surprise.
- Settled slabs cause door and window misalignment that locks up once an addition ties in. The valley’s clay soil expands and contracts with irrigation cycles, and we see original slab settlement on nearly every street from Mills to Central. We level and repair before tying in new footings.
- Failed waterproofing on original garage slabs leaks moisture into a new ADU. Garage conversions are the most common addition type in Montclair, and the original slab often lacks a vapor barrier. We install under-slab vapor barriers and retrofit drainage before framing goes up.
- Undersized framing in original single-car garages can’t carry the roofline of a new addition. Many Montclair garages were built with 2×4 rafters on 24-inch centers, which doesn’t meet current code for living space. We reinforce or reframe before drywall.
Pricing for Home Addition Contractor in Montclair, CA
Here are real numbers for Montclair work: a bump-out addition runs $22,000 to $48,000, a bathroom addition $38,000 to $72,000, a standard room addition $45,000 to $140,000, and a garage conversion to an ADU $95,000 to $180,000. Sunrooms sit at $28,000 to $65,000. These ranges include the code upgrades a Montclair permit triggers – electrical service, slab repair, waterproofing – because we write allowances for all of it into the contract. The written price includes everything we know will be required, and any discovery gets priced and approved in writing before we proceed. Call (831) 292-4191 for a free estimate on your specific addition.
We Also Serve Cities Near Montclair
Our crews serve homeowners across the Inland Empire corridor, including Montclair, plus Ontario, Upland, Chino, and Mira Loma. If you’re in a neighboring city and planning an ADU, garage conversion, or room addition, the same written-price commitment and 365-Day Done Right Promise applies. Call (831) 292-4191 to get a real number in writing.
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 Home Addition Contractor in Montclair
Converting an attached garage in Montclair typically triggers an electrical service upgrade to 100 or 200 amps, installation of a dedicated circuit for the new living space, under-slab vapor barrier retrofitting, and structural reinforcement of the original garage framing to meet current residential code. The City of Montclair’s ADU ordinance streamlines the garage conversion approval, but the building code still applies. Call (831) 292-4191 for a free estimate that includes these upgrades in writing.
Most Montclair lots are 6,000 square feet or smaller, which means the original attached garage is usually the only practical location for an ADU, and room additions typically build outward from the rear or side of the home where setbacks allow. The city’s ADU ordinance recognizes this and streamlines attached garage conversions specifically because detached units often can’t fit. Our design process starts with the lot survey and setback limits, not the floor plan.
Often yes. Montclair’s original slabs have settled unevenly over decades, and tying a new addition into a settled slab locks in the misalignment permanently. We inspect the slab before design, level and repair where needed, and include slab work in the written price. Call (831) 292-4191 to schedule a free slab and foundation inspection with your estimate.
Montclair’s inland valley heat means additions need higher R-value wall and ceiling insulation, and the dry summers demand glazing with low-E coatings and tight air sealing to keep cooling costs down. We also spec under-slab vapor barriers as standard because the original slabs were poured without them, and moisture intrusion is a common failure point. These are materials choices we make for every Montclair project, not upgrades we upsell.
Yes. Montclair requires a building permit for any attached addition, including a three-season sunroom, and the permit review includes setback compliance, slab or footing plans, and structural tie-in to the existing roofline. Unpermitted sunrooms create problems at resale and often fail inspection when discovered. We handle the permit, the plans, and the inspections as part of every project, and the written price includes all permit fees.
Written by Russ Delmar, Owner at Lodgewick ADU Riverside, serving Montclair since 2010.
