A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateADU Company in Brentwood, CA
Brentwood homeowners adding an ADU, guest house, or home addition are usually working with larger lots, newer suburban builds, and Contra Costa County’s specific setback and permitting rules. That changes how we approach everything from foundation work to panel delivery. Benson ADU Builders handles ADU construction, home additions, and room additions across Brentwood with a written price before any work starts, and a live person answering the phone at (903) 568-7222 when you call.
Why Brentwood Homes Are Different
Brentwood’s housing stock skews newer than a lot of Bay Area cities. Large subdivisions off Balfour Road and Fairview Avenue were built between the late 1990s and mid-2010s, which means most foundations are post-tension slabs, not raised floors. That’s actually good news for ADU work: slab-on-grade construction tends to make foundation tie-ins more predictable, and we don’t usually fight the rot and settling you see in older East Bay homes.
What does change the job is heat. Brentwood regularly hits the high 90s in July and August, so scheduling exterior work like stucco, roofing, and James Hardie cladding around the hottest stretch matters for material curing. We sequence exterior work for early mornings when possible and stage panel deliveries to avoid warping. The other Brentwood-specific factor is lot size: many homes sit on 6,000 to 10,000 square-foot parcels, which gives us real room to work with setbacks and still leave you a usable backyard.
Our Main Brentwood Services
Brentwood homeowners call us most about two things: building a detached ADU in the backyard, and expanding the existing footprint with a home or room addition. Each service has its own Brentwood page with full pricing and details.
ADU Builders in Brentwood
A detached ADU on a Brentwood lot typically runs 400 to 1,200 square feet, and we build them using both site-built framing and prefab panel systems from brands like Cover and Dvele. Prefab often trims weeks off the schedule, which matters when a Brentwood summer is bearing down on your job site. Setbacks and lot coverage are the two rules that shape most backyard ADU designs here, and we handle the Contra Costa County permitting package from the first conversation. ADU Builders in Brentwood covers costs, timelines, and both prefab and custom options.
Home Addition Contractor in Brentwood
A full home addition in Brentwood means expanding square footage onto an existing slab or adding a second story, which requires engineering sign-off and usually a longer permit review. Many Brentwood homes were framed with 2×4 or 2×6 standard lumber, and tying a new wing into that structure is straightforward when we expose the existing framing. You get a written price for the entire addition before we pull the first permit. Home Addition Contractor in Brentwood breaks down what a typical addition costs per square foot in this market.
Room Addition Contractor in Brentwood
Room additions in Brentwood, like adding a primary suite or a home office bump-out, are the fastest route to more livable space without a full ADU build. Whether you’re converting part of a three-car garage or extending a bedroom wall, the job hinges on roofing tie-in and floor elevation matching. On Brentwood’s flat lots, elevation matching is usually clean, which keeps costs down compared to hillside cities. Room Addition Contractor in Brentwood has the per-square-foot figures and typical project timelines.
What happens when you call
- 1
A real person answersNo phone trees - you reach a local pro.
- 2
You get an upfront price rangeHonest numbers before anyone is dispatched.
- 3
A background-checked tech heads outLicensed & insured, dispatched right away.
- 4
You approve before work beginsNothing starts until you say go.
Brands We Service in Brentwood
We’re authorized to build with Cover, Dvele, and Mighty Buildings prefab systems, and we stock James Hardie cladding and common panel fasteners locally so we’re not waiting on a warehouse run mid-project. Turnaround on parts and replacement panels is usually days, not weeks. See our brands for the full lineup.
Pricing for ADU Company in Brentwood, CA
| Service | Typical range in Brentwood |
|---|---|
| Detached ADU (400 – 800 sq ft, prefab) | $180,000 – $320,000 |
| Detached ADU (800 – 1,200 sq ft, site-built) | $320,000 – $550,000 |
| Garage conversion to ADU | $120,000 – $220,000 |
| JADU (attached, up to 500 sq ft) | $90,000 – $180,000 |
| Primary suite addition | $140,000 – $260,000 |
| Second-story addition | $250,000 – $450,000 |
| Home office room addition (150 – 250 sq ft) | $70,000 – $140,000 |
| Prefab panel delivery and set | $25,000 – $60,000 |
What pushes a Brentwood ADU or addition toward the top of those ranges: site prep on lots with drainage issues, upgraded foundation requirements from Contra Costa County, and premium prefab brands like Dvele or Mighty Buildings instead of entry-level panels. Whatever the number is, you’ll see it in writing before we start, because every Benson ADU Builders project includes an upfront written price under The Relay Visibility Guarantee.
Neighborhoods We Serve in Brentwood
We work across Brentwood every week. Most of our calls come from the suburban subdivisions south and east of downtown, but we also handle rural parcels north of Balfour Road where setbacks and well or septic lines add a layer to the plan. Here are a few of the neighborhoods we regularly serve:
- Garibaldi Ranch
- Sterling Preserve
- Arbor
- Shadow Lakes
- Downtown Brentwood
For most Brentwood addresses, we can get a technician out for an initial site visit within a few business days. Estimates are free, and scheduling is done by a live person, not a booking bot.
Service Area – Cities Near Brentwood
Benson ADU Builders also serves homeowners in other parts of the Bay Area and beyond. If you’re just outside Brentwood, you can still reach the same team. See our coverage in Ojai, CA, Oak View, CA, Ventura, CA, and Santa Paula, CA.
Serving Brentwood, CA - Our Local Coverage Area
We’re based in the Brentwood 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 ADU Company in Brentwood
We usually schedule an initial site visit in Brentwood within a few business days of your call. The visit includes measurements, a look at your lot’s setback situation, and a conversation about which ADU or addition type makes sense for your budget. Call (903) 568-7222 and a live person will get you on the calendar.
Some Brentwood subdivisions with HOAs, particularly newer planned communities, require architectural review before you build an ADU or addition. California state law limits how much an HOA can restrict ADUs, but we always recommend checking your CC&Rs early. We can include that review step in your permitting package.
Yes. Every ADU, JADU, home addition, and room addition we build in Brentwood goes through the Contra Costa County permit process, and we pull all permits ourselves. Your written price includes permit fees, and we don’t start structural work until the permit is in hand.
If you have a specific prefab brand in mind, we can tell you whether it’s viable for your Brentwood lot and budget. We build with several prefab systems, including Boxabl and Mighty Buildings, and we’ll give you honest feedback on what works for your specific setback and site conditions. Call (903) 568-7222 for a free estimate and a straight answer.
Ready to put a written price on your Brentwood ADU or addition? Call Benson ADU Builders at (903) 568-7222 and we’ll schedule your free estimate. You’ll talk to a person, get a number you can actually budget around, and know exactly what happens next before anyone picks up a hammer.
What happens when you call
- 1A real person answersNo phone trees - talk to a local adu pro.
- 2You get an upfront price rangeHonest numbers before anyone is dispatched. No surprises.
- 3We come out and measureLicensed & insured, at a time that suits you - the visit and the quote are both free.
- 4You get the price in writingLine-itemed, yours to keep, and nothing starts until you say go.
What Brentwood Customers Say
"Booked a consult online and met the project manager two days later. Weekly progress updates arrived by text with photos. ADU finished on schedule."
- Hannah W."Clean, quiet crew. They respected the neighbors, kept noise to working hours, and swept the driveway every evening."
- Hope C."Communication was the best part. I always knew what was happening that week without having to ask."
- Dolly N.
