Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
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AfterFast, Reliable Home Additions & ADU Across San Bernardino
If you live in San Bernardino and you’re trying to add square footage, you likely already know the tough part isn’t the hammering. It’s the paperwork, the seismic requirements, and the fear that your price will balloon after they start digging. A typical home addition in San Bernardino runs $45,000 to $130,000, while a new detached ADU generally lands between $90,000 and $220,000. We’re Barrett & Sons Construction, and we handle the entire process, from the first sketch through the final inspection. Call (877) 610-1318 and we’ll walk your property with you, no charge for the estimate.
We know this city’s housing stock because we work on it every week. The post-WWII slab-on-grade tract homes in the central and east-side neighborhoods of San Bernardino, particularly the 92410 and 92411 ZIP codes, were built over alluvial soil that moves with every wet-dry cycle. That movement shows up as foundation cracks, and it changes how an addition needs to be tied into the existing structure. You can’t just pour and frame. You need to understand what’s already under the slab.
Why Barrett & Sons Construction Is San Bernardino’s Preferred Home Additions & ADU Company
Tom Barrett founded this company in 1998, and his sons run the crews. That’s not marketing language. When you sign with us, the person who signs the contract is the person you’ll see on the job site. We publish Tom’s name, address, and license number, and we encourage people to look it up before signing anything. The contractor who hides his license number is usually hiding something else too.
Our San Bernardino customers tend to come to us after a bad experience with an out-of-town outfit. They tell us the same story: a low phone quote, a crew they didn’t recognize, and a final invoice that looked nothing like the first number. We do it differently. Every scope, every allowance, every price change arrives as a written change order before the work starts. An allowance that isn’t on paper is a surprise waiting for a date. Ask anyone on your street, or look up the license number yourself.
Our Home Additions & ADU Services in San Bernardino
ADU Design & Permitting
San Bernardino’s permitting desk sees things other cities don’t. If you’re in the 92404 or 92407 foothills, your ADU might trigger an Alquist-Priolo fault-setback study, a Wildland-Urban Interface review, and a hillside grading check all at once. We prepare submittals that anticipate those requirements before the first rejection arrives. Our Home Additions & ADU team handles the plan set, the geotech coordination, and the counter visits, so you don’t spend your Saturdays at Development Services.
Garage Conversion ADU
A garage conversion in San Bernardino typically runs $30,000 to $80,000, and it’s often the fastest legal way to add a rental or in-law unit to a lot you already own. The catch is that many garages here, especially the detached ones behind 1940s and 1950s tract homes, were never built to current seismic or insulation standards. We strip them to the studs, upgrade the shear wall, and bring the whole structure up to code. What looks like a simple flip is usually a structural rebuild.
New Detached ADU
Building a new detached ADU on a San Bernardino lot means working with the soil you have. Expansive alluvial ground in the central and east-side neighborhoods of San Bernardino shrinks and swells, so we spec the foundation accordingly. A new detached ADU here runs $90,000 to $220,000. That range reflects square footage, utility trenching, and the seismic detailing required this close to the San Andreas Fault. You’ll see every number in writing before we move dirt.
Junior ADU & Interior Conversion
A junior ADU, typically carved out of an existing bedroom or bonus room, is the most budget-friendly route for homeowners who need a separate living space without a separate foundation. These conversions in San Bernardino usually run $45,000 to $90,000 depending on how much kitchenette work and egress work the plan requires. The permit path is simpler than a full ADU, but it still demands its own kitchenette, its own entrance, and its own smoke and carbon monoxide coverage. We handle all of it.
What happens when you call
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A real person answersNo phone trees - you reach a local pro.
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You get an upfront price rangeHonest numbers before anyone is dispatched.
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A background-checked tech heads outLicensed & insured, dispatched right away.
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You approve before work beginsNothing starts until you say go.
Trusted Brands We Service in San Bernardino
We don’t install mystery materials off a van. For hardscape and exterior work that often accompanies an ADU or room addition, we carry Techo-Bloc and Cambridge Pavers, both brands you can look up and verify. For concrete and block work, we use Quikrete products that the local supply houses in San Bernardino stock consistently. That matters when a project is mid-construction and you need one more pallet of product. Naming the brand means you can price-check us, and we’re fine with that. No hiding behind vague “premium materials” language. You’ll know exactly what’s going into your walls, your slab, and your patio.
Common Home Additions & ADU Problems We See in San Bernardino Homes
- Cracked slabs from expansive soil. The 1940s-to-1960s tract homes across central and east San Bernardino sit on alluvial soil that expands when wet and shrinks when dry. We see slab cracks that run the full length of a floor before anyone notices them. An addition tied to that slab without proper isolation joints will crack within the first two years.
- Missing seismic upgrades on pre-1980 structures. San Bernardino sits closer to the San Andreas Fault than almost any other major Southern California city. Older homes here, especially the unreinforced masonry and pre-code wood frame builds, often lack the shear panels and anchor bolts a modern addition requires. We bring the whole assembly up to current seismic standards, not just the new room.
- Santa Ana wind stress on framing. The Cajon Pass channels wind into San Bernardino with more force than neighboring valley cities get. We see roof and wall framing that was never designed for that repeated loading. Every addition we build here gets upgraded sheathing and fastener schedules, not the minimum the code book allows.
- Fire zone requirements in the northern foothills. The 92404 and 92407 ZIP codes fall inside California’s Very High Fire Hazard Severity Zone. That means ember-resistant vents, non-combustible eave assemblies, and defensible-space grading on virtually every permit. Out-of-town contractors often learn this when the city rejects their first submittal. We build to those requirements from the first plan sheet.
Pricing for Home Additions & ADU in San Bernardino, CA
A room addition in San Bernardino runs $45,000 to $130,000. A garage conversion ADU lands between $30,000 and $80,000. A new detached ADU is $90,000 to $220,000. Those are honest San Bernardino numbers, not national averages dressed up as local pricing. What moves you within each range: the condition of your existing foundation, whether your lot needs geotechnical work, how far the utility trench has to run, and whether you’re in a fire hazard severity zone that changes your exterior materials list. We give free written estimates, and every change after the contract is a written change order. Call (877) 610-1318 and we’ll give you real numbers for your specific lot, not a generic brochure range.
We also handle Kitchen Remodeling in San Bernardino and Bathroom Remodeling in San Bernardino when a full addition isn’t the right call. Sometimes a reworked floor plan gets you the space you need without moving a single exterior wall.
We Also Serve Cities Near San Bernardino
While this page focuses on San Bernardino, our crews work the surrounding neighborhoods too, including Muscoy, Highland, Loma Linda, and Rialto. If you’re on the edge of town or just over a city line, we still want to talk. Our Home Additions & ADU in San Bernardino work regularly takes us to properties in those nearby communities, and the seismic and soil conditions are often identical.
Serving San Bernardino, CA - Our Local Coverage Area
We’re based in the San Bernardino 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 - Home Additions & ADU in San Bernardino
A home addition in San Bernardino typically costs $45,000 to $130,000 depending on square footage, foundation condition, and whether your lot triggers seismic or fire-zone requirements. A detached ADU runs higher, usually $90,000 to $220,000. The best way to get a real number is to have someone walk the property, which we do for free. Call (877) 610-1318 and we’ll come out, look at your slab, check your lot conditions, and hand you a written line-item estimate.
Yes, in most cases. The northern foothill ZIP codes of San Bernardino, 92404 and 92407, fall within California’s Very High Fire Hazard Severity Zone, which adds requirements for ember-resistant vents, non-combustible eaves, and defensible-space grading. We design your ADU plans to meet those requirements from the start, so the permit review doesn’t stall. Call (877) 610-1318 and we’ll tell you exactly which requirements apply to your specific lot.
Yes. Every eligible job includes permits pulled and inspections signed. The permit inspector works for you, not for me, which is exactly why I like him. If a contractor tells you permits are optional on an ADU, walk away. In San Bernardino, an unpermitted ADU will come back to bite you when you sell, refinance, or try to insure the property. We don’t cut that corner.
Only if the scope changes, and only in writing. If you add square footage, upgrade your materials, or we discover something under the slab that no one could have seen, you’ll get a written change order before that work begins. No surprise invoices at the end. That’s the Barrett & Sons way, and it’s written into every San Bernardino contract. Call (877) 610-1318 and we’ll show you a sample contract so you can see exactly how the numbers work.
You call Tom. Every construction and remodeling job carries our written 90-Day Done Right Promise. If it’s not done right, Tom comes back and makes it right, one call. That promise is printed on the contract, not buried in fine print. We live twenty minutes away; if something’s wrong, we want to know about it. Call (877) 610-1318 and we’ll schedule your free estimate.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving San Bernardino and the surrounding Inland Empire.