A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateFast, Reliable Room Addition Contractor Across Commerce
Adding a room to a house in Commerce usually comes down to one question before any framing starts: does your lot even have the legal room to go wider, or does the project need to go up or convert what’s already there? Most single-family lots here sit on compact parcels platted decades ago, and many rear yards are only 15 to 20 feet deep. That single fact shapes every scope, price, and permit we write. We’re Benson ADU Builders, and we start every Commerce project with a written lot-coverage and setback check, then a written price, before any work begins. Call (903) 568-7222 for a free estimate.
Why Benson ADU Builders Is Commerce’s Preferred Room Addition Contractor Company
Commerce homeowners tell us the same thing: other contractors gave them a verbal number, drew something that crossed the property line, or never came back after the first site visit. We do it differently. Led by Troy Eastman, our Room Addition Contractor team puts the scope in writing from the first conversation. The written price includes the permit path, the foundation detail, the framing, the finishes, and the inspections. No missing line items that show up later as a change order.
Our crews work in Commerce regularly, from the streets around Veterans Park to the homes off Slauson Avenue and Bandini Boulevard. That local repetition matters. We already know which lots in Commerce will hit a rear-yard setback wall and which can support a side bump-out. We’re part of the Relay Home Co. family, founded in 2006, and every project carries the 365-Day Done Right Promise: if it isn’t done right within a full year, we make it right. In writing.
You’ll also get background-checked, uniformed technicians on your property, and a live person answers our phone around the clock. No phone tag. No mystery subcontractors. Just a straight answer and a schedule you can track.
Room Additions in Commerce
Room additions in Commerce mean building conditioned, permitted living space onto an existing home, and here the first question is always the same: out, up, or convert? With rear yards as shallow as 15 feet on many streets near Slauson Avenue, going out often stops at the lot-coverage limit. That pushes many projects upward as a second-story addition or inward as a garage conversion. A typical site-built room addition in Commerce runs $180 to $340 per square foot, so a 400-square-foot bedroom-and-bath addition lands between roughly $72,000 and $136,000 before fixtures and finishes. The final number depends on foundation type, roof tie-in complexity, and whether the city requires a full plan-check cycle.
Garage conversions and bump-outs
Where the lot allows, we frame bump-outs with a new slab edge, insulated walls, and cladding options like James Hardie lap siding. Where it doesn’t, we convert a detached or attached garage into conditioned space, which triggers its own egress, utility, and insulation requirements.
Permit and inspection path
Every Commerce room addition we build goes through the city’s permitting and inspection process. That usually includes a plan check, foundation inspection, framing inspection, and final sign-off. We pull the permits, schedule the inspections, and make sure the work passes before anyone calls the project done.
Modular Home Addition in Commerce
Modular home additions in Commerce use factory-built panels or modules from brands like Abodu, Cover, and Dvele, then assemble them on your lot. The appeal is speed and predictable quality, and that’s real. But buyers need to know one thing before they commit: the module price is not the project price. Site work, foundation, utility trenching, and the local inspection path are separate line items, and on Commerce’s tight lots those costs can be substantial. A modular addition in Commerce typically runs $220 to $400 per square foot all-in, so a 400-square-foot prefab room addition often lands between $88,000 and $160,000 depending on access, foundation type, and whether utility upgrades are required.
Prefab panel systems
We work with Abodu and Cover for panelized builds, and Dvele for higher-end modular options. Each has different site-prep needs. We scope the full package in writing before any deposit changes hands, so the number you approve is the number you pay.
Site work matters most here
On compact Commerce lots, crane access, material staging, and foundation excavation can add real cost that a module-brochure quote won’t show. We include all of it in our written estimate. If a modular plan won’t fit your lot’s coverage limit, we’ll tell you before you spend a dollar on design fees.
Trusted Brands We Service in Commerce
We build with names you can research independently, and we stock local parts and materials for Commerce customers so lead times stay short. That includes James Hardie cladding for site-built additions and Abodu, Cover, and Dvele for modular and panelized projects. Troy Eastman and the crew know these systems well enough to give you an honest comparison: which option fits your lot, your timeline, and your budget in Commerce, not just which one ships fastest.
Common Room Addition Contractor Problems We See in Commerce Homes
- Skipping the lot-coverage and setback check. On a compact Commerce lot, an addition planned for the rear yard can cross the legal line before drawings are even finished. We run that check before anything else, and it has saved homeowners from paying for redesigns they never needed.
- Assuming a garage conversion is automatic. Converting a detached garage to living space changes egress, insulation, and utility requirements. It’s not the same as a bump-out, and it needs its own permit path and inspections.
- Quoting a modular addition as a turnkey number. An Abodu or Cover module price that doesn’t include foundation, trenching, and inspection fees is not a real quote. We see homeowners burned by that gap more often than any other single mistake.
- Underestimating plan-check and inspection time. Commerce’s small-lot projects often get flagged for code review at the coverage stage. A realistic calendar from day one keeps the project moving instead of stalling mid-drawings.
Pricing for Room Addition Contractor in Commerce, CA
Here’s what Commerce homeowners should expect to pay. Site-built room additions run $180 to $340 per square foot. Modular or prefab additions run $220 to $400 per square foot all-in. A garage conversion in Commerce typically lands between $60,000 and $120,000 depending on egress work, utility upgrades, and whether you’re adding a bath. A second-story addition runs higher because of roof demolition, stair framing, and structural reinforcement. What changes the price once work starts? Undiscovered conditions behind walls, foundation surprises, and plan-check corrections that require revised drawings. We can’t eliminate all of those, but our written price means you’ll see every change in writing with a line-item reason before it gets approved. Call (903) 568-7222 for a free estimate, and we’ll put the number in front of you before you decide anything.
We Also Serve Cities Near Commerce
Our Commerce crews also cover projects in Los Angeles, Long Beach, Anaheim, and Riverside. If you’re just outside the city line, we’ll still come out, walk the lot, and write you a real number. Dispatch is coordinated from the brand’s Los Angeles office, and crews serve Commerce locally.
Serving Commerce, CA - Our Local Coverage Area
We’re based in the Commerce 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 Room Addition Contractor in Commerce
Yes, but the project usually has to go up or convert existing space rather than push outward. Commerce’s compact lots frequently hit their rear-yard setback and lot-coverage limits with even a modest bump-out, so we scope a second-story addition, a garage conversion, or a bump-out that stays inside the legal envelope. Call (903) 568-7222 and we’ll run the coverage check for your parcel before you pay for any design work.
Often yes. A garage conversion in Commerce typically runs $60,000 to $120,000, while a site-built addition of similar square footage usually lands higher because it requires new foundation, roof tie-in, and exterior walls. But a garage conversion isn’t automatically cheaper once you add egress windows, insulation, and a new electrical subpanel. We’ll line-item both options so you can compare real numbers, not guesses.
A typical permitted room addition in Commerce takes 4 to 7 months from drawings to final sign-off, and it usually includes plan check plus three to five on-site inspections covering foundation, framing, electrical, and final occupancy. Your timeline depends on how fast the city processes plan corrections and how complex your lot’s coverage situation is. We schedule every inspection and keep the calendar visible to you the whole time.
No. A modular or prefab addition from Abodu, Cover, or Boxabl still requires the same city permits and inspections as a site-built room. The module itself is factory-made, but the foundation, utility connections, and placement on your lot are all permitted site work. Anyone who says otherwise is selling you a problem. We handle the full permit package on every modular build and include those fees in our written price.
The honest answer: what we find behind the walls and under the slab. In Commerce, older homes sometimes have unpermitted past work, undersized foundations, or utility lines that need upgrading to support new living space. When that happens, you get a written change order with a line-item reason before anything proceeds. We don’t bill surprises after the fact. Call (903) 568-7222 to get your free estimate started.
Written by Troy Eastman, Owner at Benson ADU Builders, serving Commerce since the company’s founding in 2006.
