Fast, Reliable New Detached ADU Across San Bernardino
A new detached ADU in San Bernardino typically runs $220,000-$380,000 all-in for a custom build, or $165,000-$280,000 for a prefab or modular unit, with final cost driven by whether your parcel sits in a fault zone, a fire hazard area, or both. We’re Nadia Ellery’s team at Ellery ADU Studio, and we’ve designed, permitted, and built ADUs across San Bernardino since 2015 - from the North End foothills near Shandin Hills to the post-war grid south of the 210. Dispatch and scheduling are coordinated from our Inland Empire office, and crews serve San Bernardino directly. Call (840) 212-3065 to schedule your free estimate.
Why Ellery ADU Studio Upland Is San Bernardino’s Preferred New Detached ADU Company
We’ve completed detached ADUs on parcels from Kendall Drive to the base of the Cajon corridor, and our permit sets move through San Bernardino Building & Safety because we know the post-bankruptcy workflow - lean staff, slower plan-check cycles, and the specific documentation triggers that out-of-area builders miss. Our clients in San Bernardino receive a written price before any work starts, per Haven Standard Clause 1, plus a documented photo record on every visit and a 365-Day Done Right Promise backed in writing.
Our reviews from San Bernardino homeowners consistently cite two things: the fault-zone discovery we flag during bidding, not after permits are submitted, and the HVAC specs that actually hold up through August. A live person answers our phones 24/7 - no voicemail queue. We also offer a Free Second Opinion on any written estimate already in hand.
Our New Detached ADU Services in San Bernardino
Custom Built ADU
Our New Detached ADU team designs and builds stick-framed detached units from foundation to final inspection under a single contract. In San Bernardino, custom builds on north-end parcels near Shandin Hills routinely require CGS fault-rupture hazard studies ($3,000-$8,000) and enhanced seismic detailing that Fontana or Riverside builders rarely encounter - we build this into our discovery checklist from the first site visit, not mid-permit. A typical custom 1-bedroom detached ADU in San Bernardino runs $260,000-$340,000 all-in; a 2-bedroom runs $320,000-$380,000. These ranges include drawings, permit set, foundation, utility tie-ins, and final inspection.
Prefab ADU Installation
We specify and coordinate prefab systems from Abodu, Cover, and Dvele within the same single contract that covers design, permitting, and site prep. Prefab units work well on San Bernardino’s flatter, non-fault-zone parcels south of the 210, where foundation requirements are standard and crane access is straightforward. A prefab studio ADU in San Bernardino typically runs $165,000-$220,000 all-in; a 1-bedroom runs $195,000-$260,000. The savings come from factory fabrication, but the site work - utility trenching, panel upgrades, and any VHFHSZ compliance - is still local and still documented in your written price before signing.
Modular ADU
Modular construction from brands like Dvele or Plant Prefab allows multi-module 2-bedroom configurations that ship in sections and crane-set on your foundation. In San Bernardino, modular ADUs make sense when you need speed on a non-fault-zone parcel and want the engineering pre-certified. We coordinate the factory specs with San Bernardino’s Building & Safety requirements, including any fire-department access or utility-separation rules. Modular 2-bedroom detached ADUs in San Bernardino typically run $240,000-$280,000 all-in, with foundation and site work quoted separately in writing.
Studio ADU
Studio ADUs - 300-450 square feet, kitchenette and bath, no separate bedroom - are the most common detached unit we permit in San Bernardino. They’re ideal for the city’s large post-war lots, where setback rules still allow a meaningful structure behind the main house. On a 1940s two-car-garage lot off Kendall Drive in the North End, our crew set a new detached studio ADU on a post-tension slab with a CGS fault-rupture letter in hand, then spec’d 26-gauge standing-seam roofing with hot-dip galvanized fasteners and James Hardie ignition-resistant siding for the VHFHSZ edge. The owner’s original 100-amp panel and galvanized supply lines were upgraded in the same scope before the city would sign off, and the AHU was oversized to hold 75°F through a 108°F August week rather than the mid-valley tonnage a coastal builder would have quoted. Studio ADUs in San Bernardino typically run $220,000-$280,000 custom, or $165,000-$210,000 prefab.
1-Bed & 2-Bed ADU
One-bedroom detached ADUs in San Bernardino range from 450-600 square feet; two-bedroom units run 600-850 square feet. Both trigger stricter utility calculations in San Bernardino Building & Safety - a 1-bedroom with electric range and dryer often pushes a 100-amp main panel past capacity, and a 2-bedroom almost always requires a 200-amp service upgrade. We identify this during discovery, price it in writing, and coordinate Southern California Edison’s timeline so it doesn’t become a schedule surprise. 1-bedroom detached ADUs run $260,000-$320,000; 2-bedroom units run $320,000-$380,000 in San Bernardino’s current market.
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.
Trusted Brands We Service in San Bernardino
We specify and coordinate prefab and modular systems from Abodu, Cover, Dvele, Mighty Buildings, Boxabl, Plant Prefab, Tuff Shed, and James Hardie within the same single contract. For San Bernardino’s VHFHSZ foothill parcels, we frequently default to James Hardie fiber-cement siding and ignition-resistant trim - materials that satisfy fire-department plan check without the change orders that vinyl or wood-composite exteriors trigger. Hot-dip galvanized fasteners and stainless-steel hardware are standard on our San Bernardino specs, not upgrades, because the city’s temperature swings and Santa Ana wind cycles corrode lesser hardware within five years.
Common New Detached ADU Problems We See in San Bernardino Homes
- Fault-zone surprises on North End bids. Contractors from Riverside or Fontana bid a detached ADU near Shandin Hills without a $3,000-$8,000 CGS fault-rupture review, then discover the study mid-permit and re-engineer the foundation. We flag this on the first site visit and build it into the written price.
- Undersized HVAC in the heat trap. San Bernardino’s 105-112°F summer highs kill mini-splits sized for coastal or mid-valley loads within a season. We spec tonnage for the actual design temperature, not the manual J that works in Ontario or Rancho Cucamonga.
- VHFHSZ non-compliance on foothill parcels. Standard soffit vents, vinyl windows, and untreated fence assemblies get rejected in Very High Fire Hazard Severity Zones. We spec ember-resistant venting and ignition-resistant exteriors from the permit set forward.
- Utility upgrades buried in 1950s homes. Original 100-amp panels and galvanized supply lines won’t carry a detached ADU’s load, and San Bernardino Building & Safety won’t sign off until they’re replaced. We test and price this before permits, not after the first failed inspection.
Pricing for New Detached ADU in San Bernardino, CA
A new detached ADU in San Bernardino runs higher than the same plan in Riverside or Fontana for three specific reasons: fault-zone studies on north-end parcels, VHFHSZ material upgrades on foothill sites, and oversized HVAC for the heat trap. Here’s what we’re seeing in 2025:
| Sub-service | Typical Range in San Bernardino |
|---|---|
| Studio ADU (custom) | $220,000 - $280,000 |
| Studio ADU (prefab) | $165,000 - $210,000 |
| 1-Bed ADU (custom) | $260,000 - $320,000 |
| 1-Bed ADU (prefab) | $195,000 - $260,000 |
| 2-Bed ADU (custom) | $320,000 - $380,000 |
| 2-Bed ADU (modular) | $240,000 - $280,000 |
| CGS fault-rupture study (if required) | $3,000 - $8,000 |
| Panel/service upgrade (typical) | $4,500 - $9,000 |
Every project is quoted with a written price before any work begins, per Haven Standard Clause 1. No change orders, no door-side upsells. Call (840) 212-3065 for your free estimate.
We Also Serve Cities Near San Bernardino
Our crews work throughout the Inland Empire, including San Bernardino, Riverside, Fontana, Rancho Cucamonga, and Ontario. Each city has its own Building & Safety rhythm, utility coordination requirements, and climate loads - we adjust the spec, not just the address.
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 - New Detached ADU in San Bernardino
Yes, if your parcel sits within or adjacent to an Alquist-Priolo Earthquake Fault Zone, which covers much of the area near Shandin Hills and the Cajon corridor base. The California Geological Survey requires a fault-rupture hazard study before San Bernardino Building & Safety will issue permits, and the review adds $3,000-$8,000 plus two to four weeks to the front of the schedule. We verify fault-zone status during our first site visit and build the study into your written price. Call (840) 212-3065 to check your parcel.
Three local factors drive the gap: CGS fault-rupture studies on north-end parcels ($3,000-$8,000), VHFHSZ material upgrades on foothill sites (ember-resistant venting, ignition-resistant siding), and HVAC oversized for 105-112°F design temperatures. Riverside and Fontana don’t overlap fault zones or VHFHSZ boundaries the way San Bernardino does, and their slightly cooler summers allow smaller mechanical systems. We itemize these differences in your written quote so you see exactly what the local conditions require. Call (840) 212-3065 for an exact quote - estimates are free.
We use San Bernardino’s actual design temperature, not the manual J default for the broader Inland Empire. That typically means 20-30% more cooling capacity than the same square footage would need in Ontario or Rancho Cucamonga, plus proper duct sizing and insulation to prevent the system from running continuously and failing within a season. Mini-splits are common, but only at the correct tonnage. We specify the exact equipment in the permit set, not a placeholder. Call (840) 212-3065 to review your site conditions.
Almost always the electrical service and frequently the water supply. Original 100-amp panels won’t carry the ADU’s additional load, and galvanized supply lines don’t meet current code for new construction. San Bernardino Building & Safety requires these upgrades to pass inspection, and Southern California Edison’s timeline for service upgrades can stretch 6-10 weeks. We test existing systems during discovery, price the upgrades in writing, and coordinate utility schedules so they don’t become the critical path. Call (840) 212-3065 to schedule your site evaluation.
Yes, typically by two to four weeks, because San Bernardino’s Building & Safety department still runs lean after the 2012-2017 bankruptcy reorganization. The real schedule advantage comes from local permit-process knowledge - knowing exactly which plan-check comments to anticipate, which documentation triggers to front-load, and how to structure resubmittals so they don’t cycle multiple times. We build this institutional knowledge into every San Bernardino permit set. Call (840) 212-3065 for a realistic timeline based on your parcel.
Ready to price your new detached ADU? Call (840) 212-3065 to schedule your free estimate. You’ll receive a written price before any work starts, a documented photo record on every visit, and the 365-Day Done Right Promise - all under The Haven Standard, in writing, from day one.
Written by Nadia Ellery, Owner at Ellery ADU Studio, serving San Bernardino since 2015.