New Detached ADU in San Bernardino - One Fixed Price, Permits Handled

Fast, Reliable New Detached ADU Across San Bernardino

A new detached ADU in San Bernardino typically runs $185,000-$340,000 all-in, from permit-ready drawings through final inspection, depending on whether you choose a custom stick-frame build or a prefab system like Boxabl or Plant Prefab. We’re the New Detached ADU team at Ellery ADU Studio, and we’ve designed, permitted, and built more than 900 ADUs since 2015 - many of them right here in San Bernardino’s Del Rosa, Arrowhead, and University neighborhoods. Dispatch and scheduling run from our Inland Empire office, and our crews serve San Bernardino directly. Call (760) 493-7752 to schedule your free estimate.

Call (760) 493-7752

Why Ellery ADU Studio Hesperia Is San Bernardino’s Preferred New Detached ADU Company

San Bernardino homeowners know the difference between a contractor who pulls a permit and a design-build studio that treats the permit set as the core product. We’ve worked the city’s post-bankruptcy building department long enough to understand its rhythms - the slower inspection queues, the seismic engineering review that every detached foundation must clear, and the specific code triggers that open once walls go up in a 1962 stucco tract home.

Our clients in San Bernardino receive the same documentation every time: a written price before any work starts, per Haven Standard Clause 1; a documented photo record on every visit; and the 365-Day Done Right Promise, backed in writing. No voicemail queues - a live person answers calls 24/7. And if you already have a written estimate in hand, we’ll give you a Free Second Opinion.

We’re not new to this market. We know the 100-amp panels, the uninsulated garage slabs, and the 108°F summer peaks that define detached ADU life in this basin. That local fluency is what keeps our San Bernardino projects on schedule when others stall.

Our New Detached ADU Services in San Bernardino

Custom Built ADU

A custom built ADU in San Bernardino gives you full control over layout, materials, and siting on your specific parcel - critical in neighborhoods like Del Rosa, where 7,500-12,000 sq ft lots offer genuine backyard room but 1950s-1970s tract home setbacks still govern placement. We handle the full design-build chain: measured site survey, permit-ready architectural and structural drawings, seismic engineering for San Bernardino’s active fault proximity, and construction through final inspection. Every allowance is written into the contract before signing. Under Haven Standard Clause 5 (No Surprises), the scope is locked - no door-side upsells, no scope creep.

Prefab ADU Installation

Prefab ADU systems from brands including Boxabl and Plant Prefab can compress San Bernardino’s timeline significantly, but only if the local contractor understands how to marry the manufacturer’s module to California Title 24 energy code and San Bernardino’s specific seismic engineering review. We specify and coordinate these systems under our single contract, so the designer and builder are the same entity - no blame gap when the module arrives and the foundation needs adjustment. Our prefab projects in San Bernardino typically run $165,000-$285,000 all-in, depending on module size and site utility runs.

Modular ADU

Modular ADU construction differs from prefab in scale and code pathway - modules are built to IRC standards in factory conditions, then craned onto a permanent foundation that must still clear San Bernardino’s seismic review. We’ve coordinated modular systems from Dvele and Mighty Buildings for San Bernardino clients whose lots accommodate the crane swing and transport access. The factory build reduces weather delay, but the site work - utility trenching, foundation engineering, and city inspection scheduling - remains local and critical. We manage both halves.

Studio ADU

A studio ADU in San Bernardino makes particular sense for homeowners who want rental income or family housing without the cost of a full one-bedroom build. We’ve built 400-550 sq ft studio detached units across Arrowhead and University, often on the same lots where a two-bedroom would crowd setbacks. The smaller footprint doesn’t mean smaller documentation - every studio gets the same permit set, photo record, and written price guarantee. In San Bernardino’s heat basin, we specify Title 24 insulation packages and properly sized mini-split systems that can hold 78°F indoors when it’s 108°F outside. Undersized HVAC is a common corner-cut we refuse to make.

1-Bed & 2-Bed ADU

One-bedroom and two-bedroom detached ADUs in San Bernardino start around $220,000 and $275,000 respectively, all-in, for stick-frame custom builds on straightforward sites. The price moves with kitchen and bath fixture choices, but more significantly with what the inspection-first process reveals: panel upgrades, foundation conditions, and utility trenching lengths. We price these items as written allowances before construction, not as change orders after walls are open. A two-bedroom ADU on a 10,000 sq ft lot in north San Bernardino is genuinely achievable; the same project on a 6,000 sq ft parcel in a coastal city would face setback variances that add months.

Trusted Brands We Service in San Bernardino

We specify and coordinate prefab and modular systems from Boxabl, Plant Prefab, Tuff Shed, and James Hardie within our single-contract design-build model. For San Bernardino’s climate - that trapped basin heat, the freeze-risk winter nights - we favor James Hardie fiber-cement siding and properly engineered insulation packages over materials that degrade faster under thermal cycling. We don’t stock parts in the abstract; we specify the right system for your specific site, pull the permit set that proves it, and coordinate delivery to align with San Bernardino’s inspection schedule. Every brand choice is documented in your contract, not selected at the lumber yard.

Common New Detached ADU Problems We See in San Bernardino Homes

• Undersized electrical panels. That 100-amp Zinsco or Federal Pacific panel in your 1964 garage was never meant to carry a second dwelling. We find this on the first inspection, price the 200-amp upgrade as a written allowance, and lock it into the contract before framing starts - not after the city inspector red-tags the rough electrical.
• Seismic engineering delays. San Bernardino’s position above active San Andreas-system fault strands means every detached ADU foundation must clear a structural engineering review that contractors in Fontana or Rialto rarely encounter. Skip it, and plan check stalls for weeks. We submit seismic calcs with the initial permit package, not as a correction.
• Freeze-risk supply lines. Winter nights in San Bernardino’s basin drop below 32°F with little warning. Exposed water lines in uninsulated slab edges crack. We address this at rough-in with proper insulation and freeze protection - a detail that costs hundreds at build time, thousands after the burst.
• Heat-gain HVAC undersizing. A mini-split rated for milder Inland Empire cities won’t hold setpoint when San Bernardino hits 108°F. We size for the actual cooling load, not the catalog’s generic zone chart, and we document the Manual J calculation in your permit set.

Pricing for New Detached ADU in San Bernardino, CA

We Also Serve Cities Near San Bernardino

Our crews work throughout the Inland Empire, including San Bernardino and the surrounding communities of Highland, Rialto, Crestline, and Fontana. Each city carries its own permitting rhythm and building stock - Fontana’s newer developments face different setback rules than San Bernardino’s vintage tracts - and we adjust the permit set accordingly rather than recycling the same drawings.

FAQs - New Detached ADU in San Bernardino