Fast, Reliable New Detached ADU Across Concord
A new detached ADU in Concord typically runs $280,000 to $420,000 all-in, from drawings through final inspection. That’s the honest range we quote for a custom one-bedroom unit on a standard Concord lot, and we put that number in writing before any work begins. It’s how we’ve built 900+ ADUs since 2015, every one under a single design-build contract.
We know Concord’s housing stock because we’re in it every week. The 1960s ranch on a 7,500-square-foot lot off Clayton Road, the split-level off Monument Boulevard with an aging sewer line, the corner property near the Concord BART station where commuter renters pay a premium for a short walk to the train. Call (971) 497-2402 and we’ll walk you through what’s possible on your lot, in plain English, with a written price at the end of the conversation.
Why Ellery ADU Studio Is Concord’s Preferred New Detached ADU Company
We’re a design-build studio founded in 2015 by Nadia Ellery, the year California’s ADU permitting landscape shifted. That timing matters. We cut our teeth exactly when setback rules, utility fees, and permitting pathways changed across Contra Costa County, which means we’re not retrofitting old contractor habits onto new ADU code. In Concord, that institutional knowledge shows up in the permit set, where our drawings reflect current Concord building department expectations and plan-review feedback we’ve now absorbed hundreds of times over.
Nadia built this practice around one principle: the drawings, the permit set, and the construction are a single contract at a single written price. There’s no designer-versus-builder blame gap, because there’s no gap at all. If a detail is wrong, it’s our detail. If a line item missed something, it’s our line item. The Haven Standard, our written project covenant, locks this in under Clause 1: a written price before any work starts, on every project, without exception.
Our teams arrive in Concord background-checked and uniformed, with a documented photo record on every visit. You’ll see what we found and what we did, not a summary of how it felt. A live person answers our phone 24/7, which matters when you’ve got a rental unit empty for a month and a line-item question that can’t wait until Monday.
Our New Detached ADU Services in Concord
Every New Detached ADU we build in Concord is one contract: the site work, the foundation, the permit set, the build, and the final inspection. Below are the four paths Concord homeowners most often choose.
Custom Built ADU
A custom detached ADU on a Concord lot is exactly that: framed on-site to match your property, your setbacks, and your long-term plan. We see a lot of Concord clients with 9,000-square-foot lots and enough room for a proper two-bedroom unit behind the existing ranch. Our custom units run $320,000 to $420,000 depending on size and interior fit-out, and the price is locked at signing under Haven Standard Clause 5 (No Surprises).
Prefab ADU Installation
Prefab is faster, not cheaper, and for some Concord lots it’s the right call. We specify and coordinate systems from Abodu and Cover, handling the site work, utilities, and foundation connection under the same contract. A one-bedroom prefab unit in Concord typically lands between $260,000 and $340,000, including site prep, utility hookups, and the permit set. The prefab factory builds the box; we build everything that box sits on and connects to.
Modular ADU
Modular units split the difference between true custom and factory-built. In Concord, we often recommend modular for mid-size lots where access is tight and a crane delivery isn’t practical but off-site framing still saves weeks. Prices run $280,000 to $380,000 for a one- or two-bedroom unit, depending on the module count and finish level. The written price includes the crane, the set, the utility tie-ins, and the final inspection sign-off.
Studio ADU
A studio ADU is the highest-ROI unit for a Concord rental: one open room, a kitchenette, a full bath, and a dedicated entry. On a standard 6,000-square-foot lot, a studio build runs $250,000 to $310,000 all-in. In Concord’s rental market, where BART commuters and hospital workers at John Muir compete for one-bedroom inventory, a properly cooled studio ADU rents fast, and we’ll tell you exactly what that unit needs to be legally leasable in summer. The short answer: a mini-split, sized for the room, not a window unit.
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 stock parts for every ADU system, but we do stock hardware for the ones we install in Concord, because waiting on a marine-grade fastener shipment while a unit sits empty is a cost you shouldn’t pay. We specify James Hardie fiber-cement lap siding for exterior cladding that survives Diablo Valley temperature swings without callbacks. We coordinate Abodu and Cover prefab systems for clients who want factory-built speed. And we standardize on Dvele for high-performance modular units where energy modeling matters to the long-term rental math.
Common New Detached ADU Problems We See in Concord Homes
- Orangeburg sewer laterals failing on 1960s ranches. Concord homes built between 1955 and 1972 frequently have sewer laterals made of compressed tar paper. When your ADU triggers a sewer lateral inspection, collapsed Orangeburg pipe adds $8,000 to $15,000 to the project budget before we can even pour the foundation.
- Original 100-amp electrical panels that can’t carry the ADU load. Most 1960s and 1970s Concord ranches were built with 100-amp service. A detached ADU with a mini-split, electric range, and laundry almost always requires a panel upgrade to 200 amps, and that’s a line item on the permit set, not a surprise at final inspection.
- Poorly sized cooling systems that make summer rental units unrentable. Concord regularly records summer highs above 100°F, and interior Diablo Valley heat doesn’t break like Oakland’s marine layer. An ADU without a properly sized mini-split will generate callbacks from tenants, and in the worst case, a habitability complaint.
- Budget zinc hardware that rusts within two seasons. The combination of valley heat and occasional marine-influenced morning fog means standard electro-galvanized hardware shows rust blooms fast. We see loose metal roof panels and corroded railing fasteners on ADUs built by other contractors within five years.
Pricing for New Detached ADU in Concord, CA
Here’s where your money goes in Concord. A custom studio ADU: $250,000 to $310,000. A one-bedroom: $290,000 to $370,000. A two-bedroom: $350,000 to $420,000. Prefab and modular units run $260,000 to $380,000 depending on the system and site work. Every one of those numbers is a written price before we start, per Haven Standard Clause 1, and it includes drawings, permits, construction, and final inspection.
What moves the number in Concord specifically: sewer lateral replacement ($8,000 to $15,000 if Orangeburg is present), electrical panel upgrade from 100 to 200 amps ($3,500 to $5,000), and site prep on lots with grade changes or retaining walls. We’ll walk your lot, give you a line-item written estimate, and you can compare it against anyone else’s. Call (971) 497-2402 for a free estimate.
We Also Serve Cities Near Concord
Our crews work New Detached ADU in Concord projects weekly, and we regularly take on builds in Pleasant Hill, Walnut Creek, Lafayette, and Martinez. The permitting bodies differ slightly, the soil conditions in Martinez near the Carquinez Strait differ a lot, but the written-price standard stays the same. If your lot sits in one of those cities, the same single-contract model applies.
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 - New Detached ADU in Concord
No, you cannot rely on a wall unit in Concord. Summer highs over 100°F are routine in the Diablo Valley, and an ADU without a properly sized mini-split is essentially unleasable in summer. Tenants will expect functioning cooling, and a window unit will not hold temperature in a properly insulated new build. We include a mini-split in every Concord ADU line item, sized to the unit’s square footage and sun exposure. Call (971) 497-2402 for a written quote, and we’ll show you the BTU math.
It triggers a sewer lateral inspection, and if the Orangeburg has collapsed or deformed, replacement is mandatory before the ADU can connect. Budget $8,000 to $15,000 for that line item if your home is in the Monument Boulevard corridor or central Concord neighborhoods where Orangeburg was standard. We identify this risk during pre-construction walkthroughs, not after the permit is pulled. Call (971) 497-2402 and we’ll check your lateral scope before you spend a dollar.
Use hot-dip galvanized or stainless steel fasteners, not standard electro-galvanized screws. Concord’s diurnal temperature swings cause rapid expansion and contraction cycling on metal roofs, and the thin zinc layer on budget screws erodes quickly. We spec hot-dip or stainless on every Concord ADU metal roof, and we’ve seen the alternative fail within five years. Estimates are free: call (971) 497-2402.
Because Concord’s inland sun exposure is more intense than coastal zones, and the UV load warps budget vinyl frames. Marine-grade powder-coated aluminum or extruded fiberglass holds its shape and seal through 100°F summers without discoloring or breaking seals. That’s not coastal-spec marketing; it’s what survives here. Call (971) 497-2402 and we’ll show you the frame specimens.
You need sealed joints with a stabilized joint compound that tolerates high heat. Concord’s 100°F-plus summer days bake standard joint sand, leading to washout and weed growth in the first rainy season. Walnut Creek gets marginally more coastal relief; Concord doesn’t. We use a heat-tolerant binder on every paver installation we do in Concord. For a written estimate, call (971) 497-2402.
Written by Nadia Ellery, Owner at Ellery ADU Studio, serving Concord since 2015.