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 Concord
A full home addition or ADU in Concord typically runs $45,000 to $130,000 for a room addition, and $90,000 to $220,000 for a detached ADU. Those are real numbers from jobs we’ve priced in this market, not national averages pulled off a chart. If you’re weighing whether to add square footage to a 1960s ranch in Concord, build a garage conversion on a lot zoned for it, or put a new detached unit in the backyard off Clayton Road, we can give you a written line-item estimate with allowances spelled out before anything gets signed. Call (877) 610-1318 and Tom or one of his sons will walk the property with you.
We’ve been out here long enough to know which Concord blocks sit on the worst of the Diablo Valley clay, which permits the city wants pulled, and which inspectors will be walking your job before the concrete cures. That matters when you’re spending six figures on an addition.
Why Barrett & Sons Construction Is Concord’s Preferred Home Additions & ADU Company
Barrett & Sons has been owner-operated since 1998, and Tom Barrett’s name is on the truck. Not a franchise logo. His sons run the crews that build additions and ADUs in Concord, and Tom answers the phone himself when you call (877) 610-1318. We pull permits on every eligible job and the inspector signs off before we call it done. Ask anyone who’s hired us in Concord, or look up the license number yourself. That’s the point.
The 90-Day Done Right Promise is written on every contract. If something’s not right within 90 days of completion, Tom comes back and fixes it. One call. Concord homeowners have taken us up on it, and we’ve honored it every time.
Every scope, every allowance, every price change arrives as a written change order before work proceeds. An allowance that isn’t on paper is a surprise waiting for a date. You won’t get that from us, because that’s the exact thing that burned most of our Concord customers before they found us.
We carry premium brands you can research: KraftMaid and Cambria in kitchens, Andersen and Marvin on windows, GAF and CertainTeed on roofs. For hardscape tie-ins on ADU projects, we use Belgard and Techo-Bloc. These are names you can look up, not mystery materials off a van.
Our Home Additions & ADU Services in Concord
ADU Design & Permitting
Concord’s planning department has its own ADU requirements, and they’ve tightened in recent years with the Villages at Concord redevelopment pushing the city to standardize accessory unit rules faster than most East Bay cities. We handle the full design and permitting package, and we know which Concord inspectors review which checkpoints. That means fewer surprises when inspection day comes. What we can’t promise is a rubber stamp, because the permit inspector works for you, not for me.
Garage Conversion ADU
A garage conversion in Concord typically runs $30,000 to $80,000, depending on whether you’re converting an attached garage in a 1950s tract home near Monument Boulevard or a detached garage on a larger lot in the Clayton Road corridor. The older Concord garages often sit on the same slab as the house, which is good for tying in plumbing and electrical, but the slab may need leveling if the native clay has done its shrink-swell work over the decades. We check that before we quote.
New Detached ADU
Building a new detached ADU in Concord runs $90,000 to $220,000, and site prep is the wild card. Lots east of I-680 and in the older flatlands of Concord have expansive Montmorillonite clay under the topsoil. A foundation that looks fine at a February walkthrough can show stress by late August, which is why we time excavation and foundation pours seasonally when we can. Techo-Bloc pavers for the connecting path and entry give the unit curb appeal that matches the primary house.
Junior ADU & Interior Conversion
A junior ADU, which is typically a converted bedroom with its own entrance and kitchenette, runs $45,000 to $130,000 depending on scope. In Concord’s dense ranch tracts, this is often the fastest path to rental income because the structure’s already there. We’ve done interior conversions in the neighborhoods off Willow Pass Road, where the original floor plans leave a bedroom with a door to the backyard, and tying it into the main sewer line without trenching the entire yard takes some planning. Our Home Additions & ADU team handles it start to finish.
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 Concord
We don’t install materials you can’t verify. On hardscape and site work tied to ADU projects in Concord, we regularly use Techo-Bloc and Oldcastle products because they hold up to the Diablo Valley’s summer heat and winter wet cycles better than the cheaper stuff. We also keep Quikrete products on hand for the smaller concrete pours that come up mid-project, which keeps a Concord job moving instead of waiting on a supply run.
Common Home Additions & ADU Problems We See in Concord Homes
- Slab cracks from expansive clay. Concord sits on Montmorillonite clay that swells in winter and shrinks in summer. Older slabs crack, and adding square footage means tying new footings into a slab that may have moved. We check this first, because it changes the foundation plan and the price.
- Pre-Title-24 insulation and wiring. Most Concord homes built between 1950 and 1975 have original insulation and electrical panels that won’t pass inspection for a new addition. Upgrading the service panel and bringing the envelope to code is part of the real cost, and we put it in writing upfront.
- Setback and lot coverage limits. Concord’s lots vary widely, from quarter-acre parcels off Clayton Road to tighter infill lots near the downtown core. An ADU that seems to fit on paper may not clear the setbacks once we survey it. We pull the survey and the permit drawings before you commit.
- Diablo wind damage to exteriors. Concord gets hot, dry offshore winds in the fall, and those gusts work on stucco, siding, and roof edges year over year. When we tie a new addition into existing exterior walls, we check what the wind’s already done so the new work doesn’t inherit old problems.
Pricing for Home Additions & ADU in Concord, CA
Here’s where the numbers land in Concord, based on jobs we’ve priced this year. A room addition runs $45,000 to $130,000. A detached ADU runs $90,000 to $220,000. A garage conversion ADU runs $30,000 to $80,000. A junior ADU or interior conversion lands around $45,000 to $130,000. If the job also includes kitchen work, our Kitchen Remodeling in Concord pricing runs $14,000 to $45,000; if it includes a bath, our Bathroom Remodeling in Concord work lands between $9,000 and $28,000.
What moves the number: whether we’re tying into existing sewer or running new lines, whether the panel needs an upgrade, whether the site needs grading for clay, and what finish level you choose. All of it goes into a written line-item estimate before you sign. Call (877) 610-1318 to schedule your free estimate. No trip charge inside the county, and we’ll give you a second opinion on any written estimate you’ve already got.
We Also Serve Cities Near Concord
Our crews work Concord every week, and we also take jobs in Pleasant Hill, Contra Costa Centre, Waldon, and Walnut Creek. If you’re in one of those nearby towns and comparing contractors, the same written change order promise applies. Barrett & Sons is the Home Additions & ADU in Concord team that shows up when we say we will.
Serving Concord, CA - Our Local Coverage Area
We’re based in the Concord 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 Concord
Once permits are approved, we can typically break ground within two to four weeks. The permitting timeline in Concord depends on the current load at the city planning desk, which has been moving faster since the Villages at Concord pushed the city to streamline ADU reviews. Call (877) 610-1318 and we’ll check where your project sits in the queue.
Yes. We work the flatlands east of I-680, the neighborhoods off Monument Boulevard and Willow Pass Road, the Clayton Road corridor, and everywhere in the 94518, 94519, 94520, and 94529 zip codes. If you’re in Concord, we’re close enough to be there when we say we will.
A garage conversion in Concord runs $30,000 to $80,000, and a new detached ADU runs $90,000 to $220,000. The conversion is cheaper because the shell exists, but the slab condition and electrical service can close some of that gap. Call (877) 610-1318 for a written line-item quote, free.
Not without a written change order that you sign first. Every scope change, every allowance adjustment, every surprise condition gets priced in writing before a single nail moves. That’s how Barrett & Sons has done it since 1998, and it’s the reason our Concord customers don’t get a different bill at the end.
It covers workmanship on every addition and ADU we build in Concord. If something’s not right within 90 days of completion, Tom Barrett comes back and makes it right, one call. The promise is written on your contract, not buried in fine print. Call (877) 610-1318 to schedule your free estimate today.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Concord homeowners with owner-operated additions and ADUs since 1998.