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 square footage in Commerce comes with a specific set of rules shaped by the city’s older housing stock and famously tight lots. A rear addition off Bandini Boulevard or a second-story bump-out near Rosewood Park is rarely a simple side expansion – most Commerce homes built in the 1950s and 60s sit on parcels where the side yard is barely wider than a walkway. That’s why our Room Addition Contractor team starts every Commerce project by checking the actual setbacks, the existing slab type, and the floor-area ratio before we put a single number on paper. Sutton ADU Builders has been building additions since 2006, and Miles Hartwell leads every scope review so you know exactly who is making decisions on your home. Call (472) 248-8213 to schedule a free estimate.
Why Sutton ADU Builders Is Commerce’s Preferred Room Addition Contractor Company
Commerce homeowners don’t get a handshake and a vague number. They get a written price before any work begins, and they get the name and photo of every technician who will walk onto their property before that person rings the doorbell. That’s the Threshold Standard, and it’s how we’ve operated since 2006 as part of the Threshold Group family. For a homeowner who is often alone during the day or has young kids at home, knowing exactly who is coming matters as much as knowing what the addition will cost.
We’ve built rear additions, garage-top rooms, and modular extensions throughout Commerce – from the residential streets near Bandini Park to the older blocks south of the 5 freeway. The 365-Day Done Right Promise is written into every contract: if anything in our workmanship fails within one full calendar year of project completion, we return and fix it at no charge, and that includes a free second visit if a repair doesn’t hold. No haggling, no fine print.
Our crews know Commerce’s permit counter, its zoning quirks, and which inspectors review which phase. That local working knowledge means the plan we price for you is the plan that actually gets permitted and built. If a setback issue or slab condition changes the scope, you hear it from us before the city does – not after a variance fee lands on your desk.
Room Additions in Commerce
Room Additions in Commerce are shaped by one hard reality: the city’s 1950s and 60s subdivisions left many single-family lots with side yards of only 3 to 4 feet. A simple side bump-out that works in a city with wider setbacks often triggers a lot-coverage variance here – or isn’t buildable at all. So most Commerce additions go rear, or they go up. A rear addition off the back of the house typically costs between $220 and $380 per square foot in Commerce depending on foundation work, finishes, and whether a bathroom is part of the scope. A modest 300-square-foot rear den with a half-bath usually lands between $85,000 and $135,000 when the existing slab can be extended without major repair.
Rear and Second-Story Additions
On a 1948 stucco ranch off Slauson Avenue near the Commerce Casino area, our crew framed a 320-square-foot rear room addition because the side yard was only 3 feet from the property line. We used James Hardie fiber-cement siding to match the existing stucco and engineered a flush beam to avoid a step-down into the original slab. The clients gained a den and half-bath without triggering a lot-coverage variance. Rear additions like this are the most common room-addition path in Commerce because they work with the lot instead of fighting it.
Second-story additions over an existing portion of the house run higher per square foot – usually $300 to $450 – because they require structural review of the lower walls and often a new stair opening. But for a Commerce lot where the rear yard is already tight, going up is frequently the only way to add two bedrooms without eating the whole backyard.
Foundation and Slab Checks Before You Commit
Commerce’s older tracts include a mix of conventional slabs and post-tension slabs. Before we trench for new plumbing or cut into an existing slab for a door opening, we verify which type you have. Cutting into a post-tension slab without that check can snap a tensioned cable and trigger a slab repair that runs five figures. We confirm this during the estimate walkthrough so the price we hand you reflects the foundation you actually have.
Modular Home Addition in Commerce
Modular Home Addition work in Commerce is a practical answer for homeowners who want the speed and predictability of factory-built construction without the full custom-build timeline. A modular addition – built off-site as a complete room or suite, then set and finished on your lot – typically runs $200 to $350 per square foot in Commerce for the structure, with site work, foundation, and utility connections adding $30,000 to $60,000 depending on the existing slab condition and trenching requirements. For a 400-square-foot modular primary suite, expect a total project range of $120,000 to $200,000 in Commerce.
Brand Options and What They Cost
We work directly with several prefab and modular manufacturers, and we’ll walk you through what each one actually delivers for a Commerce lot. Abodu units are a strong fit for rear-access lots with good crane clearance off the alley. Cover builds panelized systems that make sense when the rear yard is irregular. Dvele offers higher-performance envelopes if you’re planning a long-term multigenerational suite. The brand choice matters less than the site preparation, and on Commerce lots the site work is usually the part that surprises people.
Site Work Is the Real Number to Watch
A factory-built modular room can be framed in a week at the plant. But before it ever arrives, the pad has to be engineered, the setbacks verified, and the existing utilities located. In Commerce’s older tracts, we often find the sewer lateral runs closer to the rear property line than current code allows, which means the plumbing tie-in has to be rerouted. We scope that work as a line item in the written price, not as a “site conditions allowance” that quietly grows once the job starts.
Trusted Brands We Service in Commerce
Commerce homeowners ask us about James Hardie siding on nearly every rear addition because the existing stucco on these 1950s and 60s homes is often fatigued. We specify Hardie fiber-cement lap or panel in a color match that holds up through Commerce’s hot, dry summers and the occasional heavy winter rain. For modular work, we have direct experience with Abodu, Cover, and Dvele product lines, and we’ll tell you honestly which one fits your lot geometry and your budget – not which one we happen to be pushing that month. Because we order materials through local Los Angeles-area suppliers, turnaround on Commerce projects stays predictable. No waiting three weeks for a trim color match.
Common Room Addition Contractor Problems We See in Commerce Homes
- Tight side setbacks that kill a side addition before it starts. Commerce’s 1950s and 60s subdivisions left many homes with side yards under 4 feet. A contractor who quotes a side bump-out without checking the actual property line is pricing a floor plan that can’t be permitted. Always ask whether the quote reflects a real survey or just a guess from the assessor’s map.
- Post-tension slab surprises during plumbing trenching. Cutting into a post-tension slab without a cable map can snap a tensioned tendon. The repair often costs more than the plumbing work itself. We verify slab type before any cutting happens, and we show you the verification in the written scope.
- Flat per-square-foot quotes that ignore floor-area ratio. Commerce lots have maximum lot-coverage rules. A contractor quoting $200 a square foot with no mention of FAR is quoting a number, not a project. When the footprint gets revised mid-permit, the price moves with it. We scope the addition against Commerce’s coverage limits from day one.
- Assuming what neighboring cities allow. A side addition that flies in Bell Gardens or Maywood may not fly in Commerce. Our title search pulls Commerce’s specific setback and height standards, not a generic LA County template. If a rear or second-story solution is required, you know that before the architectural drawings are done – not after the city rejects the first submittal.
Pricing for Room Addition Contractor in Commerce, CA
Here are honest ranges for Commerce’s current market. A conventional rear room addition runs $220 to $380 per square foot depending on finishes and whether a bathroom is included. A second-story addition runs $300 to $450 per square foot because of the structural work on the lower walls. A modular addition from a brand like Abodu or Cover lands between $200 and $350 per square foot for the structure, plus $30,000 to $60,000 in site work, foundation, and utility connections on a typical Commerce lot. A 320-square-foot rear addition with a half-bath off Slauson Avenue just completed at $118,000 all-in with James Hardie siding.
What moves the price in Commerce: slab condition, whether the lot needs a soils report, sewer lateral depth, and whether the rear yard has crane access for a modular set. Every estimate includes a written, line-item price before we lift a tool. Call (472) 248-8213 for your free estimate – no phone tree, a live person answers.
We Also Serve Cities Near Commerce
Our crews work throughout southeastern LA County. In addition to our core Commerce service area, we build room additions in Los Angeles, Long Beach, Anaheim, and Riverside. If you’re just outside the Commerce line, call (472) 248-8213 and we’ll confirm coverage for your street.
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, in most cases a garage-top room addition is permitted in Commerce, but it requires a structural review of the garage walls and footing. Many Commerce garages from the 1950s and 60s were built on a thin slab with no footing designed for a second story. We typically need to add a perimeter footing or steel reinforcement, which adds $25,000 to $45,000 to the project. Call (472) 248-8213 and we’ll tell you whether your specific garage can carry the load before you spend money on drawings.
Plan check for a room addition in Commerce generally runs 4 to 10 weeks depending on whether the project triggers a zoning review. A simple rear addition that stays within the lot coverage and height standards can clear in about 6 weeks. Anything requiring a variance – typical with side additions – adds 2 to 4 months. We submit complete sets the first time, which is the single biggest factor in keeping the timeline short.
Not always. A soils report is usually required in Commerce when the addition changes the foundation system materially – for example, a second-story addition over a slab built in the 1950s, or any addition in an area with known expansive soil. A rear addition that extends an existing conventional slab may not trigger one. We’ll tell you during the estimate whether your project is likely to need the report and budget $3,000 to $6,000 for it if it does. Call (472) 248-8213 for a case-specific answer.
We specify Abodu, Cover, and Dvele most often for Commerce modular additions. Abodu fits rear-access lots with crane clearance off the alley. Cover works well on irregular rear yards. Dvele is the choice for a high-performance envelope when the addition will be lived in full-time. We’re also familiar with James Hardie exterior systems for the site-built portions and fascia work. Your lot geometry and budget drive the brand choice, and we’ll explain the trade-offs in plain language.
Yes, a permitted room addition in Commerce will increase your assessed value, which raises your annual property tax bill. The increase is based on the added square footage and the county’s assessment after the final inspection closes the permit. An unpermitted addition avoids the tax increase in the short term but creates a liability when you sell and can void coverage on a future claim. The exact tax impact depends on your current assessment and the added square footage, and it’s something we flag honestly before you sign anything. Call (472) 248-8213 for a free estimate and a straight conversation about the full cost picture.
Written by Miles Hartwell, Owner at Sutton ADU Builders, serving Commerce and southeastern LA County through the Threshold Group family since 2006.
