Trusted New Detached ADU for San Bernardino Homeowners
A New Detached ADU in San Bernardino typically costs $220,000-$450,000 all-in, from the first site survey through final inspection, depending on size, finish level, and whether you build custom or go prefab. Ellery ADU Studio has designed, permitted, and built over 900 ADUs since 2015, the year California’s ADU laws began their major shift, and every project has started with a written price before any work began. If you’re a San Bernardino homeowner who bought between 2015 and 2025 and you’re weighing an ADU as a long-term rental income asset or multigenerational housing solution, we operate as a single-contract design-build studio - drawings, permit set, and construction under one written price, with no designer-versus-builder blame gap to derail your timeline.
San Bernardino’s zoning presents specific opportunities that don’t exist in every Inland Empire city. The R-1 zones in neighborhoods like Del Rosa, Arrowhead, and the North Park area often allow detached ADUs up to 1,200 square feet without a variance, provided you meet the 4-foot side and rear setbacks - though corner lots and flag lots in the foothill zones near New Detached ADU - Highland can trigger additional review. We’ve navigated these exact conditions dozens of times. Our permit sets are built to San Bernardino County’s specific checklist, not a generic California template, and our crews know the difference between a standard plan check and the extended review required when your lot backs onto the Santa Ana River wash or sits in a Loma Linda-adjacent flood zone. Call (909) 359-6463 to schedule your free estimate. Every estimate includes a written price before you commit, per Haven Standard Clause 1.
What Our New Detached ADU Service Includes
Custom Built ADU
Custom built means your ADU is stick-framed on-site to your specifications, with full architectural control over layout, ceiling height, window placement, and exterior finish. This is the right path when your San Bernardino lot has unusual geometry - a steep grade in the Shandin Hills area, a narrow flag lot near California State University, or specific neighborhood design guidelines in the historic districts - or when you want materials and detailing that prefab systems don’t offer. At Ellery ADU Studio, our in-house designers produce the permit set, our project managers coordinate San Bernardino’s plan check and inspection sequence, and our crews build to those drawings under the same contract. The 365-Day Done Right Promise applies: if the finished ADU is not built to the permitted drawings, we make it right, in writing, before the first nail goes in.
Prefab ADU Installation
Prefab ADU installation means the unit is manufactured off-site in a controlled factory environment, then craned onto your foundation and connected to utilities. This path compresses the construction timeline significantly, which matters in San Bernardino’s inland climate where summer heat can slow on-site work. We specify and coordinate prefab systems from Abodu, Cover, and other manufacturers, handling the interface between the factory’s engineering and San Bernardino’s local codes - seismic bracing for the San Andreas fault zone, wind ratings for the Santa Ana corridor, and the specific foundation details your soil conditions demand. The written price covers factory coordination, site prep, crane rental, utility tie-ins, and final inspection. You receive one invoice, one timeline, one point of contact.
Modular ADU
Modular ADUs differ from prefab in that they’re built to the California Building Code’s modular standards, inspected at the factory by a state-approved third party, then delivered in sections for on-site assembly. This classification often streamlines San Bernardino’s local inspection process because the state-level factory approval reduces what the city needs to verify in the field. We’ve worked with Dvele and Mighty Buildings systems specifically, and we understand the documentation package required to move a modular unit from factory exit through San Bernardino’s final occupancy inspection. The foundation, utility trenches, and site work happen while the modules are in production, so the critical path runs in parallel rather than series. Your written price includes every phase, with no change orders for “discovered” conditions that we should have found in the initial survey.
Studio ADU
A studio ADU is a single-room dwelling with combined living and sleeping space, a full kitchen, and a bathroom, typically 300-450 square feet. This size class is the most common starting point for San Bernardino homeowners testing the ADU rental market, and it fits comfortably within the standard setback envelopes of most R-1 lots in neighborhoods like Del Rosa, Arrowhead, and the areas west of Waterman Avenue. We design studio ADUs with specific attention to San Bernardino’s cooling load - the inland heat demands proper insulation, orientation, and sometimes mini-split sizing that contractors from coastal markets underestimate. Our permit set includes the energy compliance documentation that San Bernardino’s building department requires, and our construction crews build to that specification, not to a cheaper shortcut that fails inspection.
1-Bed & 2-Bed ADU
One-bedroom and two-bedroom ADUs separate sleeping from living space, with the 2-bed configuration adding either a second private bedroom or a flexible den that can serve as guest space or home office. In San Bernardino’s rental market, a 1-bed ADU typically commands significantly more than a studio, and a 2-bed unit opens multigenerational use - aging parents, adult children, or live-in caregiver arrangements. These larger units push closer to the 1,200-square-foot maximum for detached ADUs under state law, which means every square foot needs to earn its place in the layout. Our designers optimize the plan for San Bernardino’s typical lot widths and depths, and our permit sets account for the additional parking, fire separation, and utility capacity that larger units require. The written price is fixed at signing; Haven Standard Clause 5 locks the scope, so no door-side upsells appear mid-project.
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.
Brands We Service for New Detached ADU
Ellery ADU Studio specifies and coordinates prefab and modular systems from Abodu, Cover, Dvele, Mighty Buildings, Boxabl, Plant Prefab, Tuff Shed, and James Hardie - not as a sideline, but as a core competency within our single-contract model. With Abodu, we’ve completed multiple installations in San Bernardino County’s inland climate zone, and we know the factory lead times, the crane access requirements for their larger two-bedroom units, and the specific foundation details their engineering team requires for the decomposed granite soils common in the foothill areas. Cover’s system, with its integrated mechanical chase and panelized construction, demands precise site prep tolerances that we’ve refined through repeated installs. We don’t resell these brands; we integrate them into a project delivery system where the permit set, the factory coordination, and the site work are one contract at one written price.
Dvele’s smart-home-integrated modular platform and Mighty Buildings’ 3D-printed composite panels represent newer construction methodologies that San Bernardino’s building department is still building familiarity with. We’ve shepherded both systems through plan check in this jurisdiction, and we know which questions the plan checker will ask, which documentation they’ll want to see, and how to avoid the back-and-forth that delays factory release. Whether your project calls for Abodu, Cover, Dvele, Mighty Buildings, or any other system, we evaluate the fit against your lot conditions, your timeline, and your budget - then we coordinate every moving part under The Haven Standard, with a written price before work starts and a 365-Day Done Right Promise when work is complete.
Signs You Need New Detached ADU Right Now
- Your mortgage payment has outpaced your income growth since your 2015-2025 purchase. San Bernardino homeowners who bought at peak pricing are carrying debt loads that strain monthly cash flow. A detached ADU generating rental income - typically $1,400-$2,200 monthly for a studio or 1-bed in San Bernardino’s current market - can restructure that equation without selling into a down market. We’ve helped dozens of homeowners in this exact position, and the permit timeline means starting now puts you closer to income generation.
- You need flexible housing for aging parents or adult children. Multigenerational living arrangements are accelerating in the Inland Empire, and a detached ADU preserves privacy and independence in a way that a shared-wall conversion or interior partition cannot. The separate entrance, kitchen, and bathroom mean genuine autonomy, and the property value increase typically outperforms the cost of equivalent assisted living or off-campus rental arrangements.
- Your garage conversion won’t work structurally or legally. Not every San Bernardino garage is a conversion candidate. Slabs too thin for habitable use, ceiling heights below 7 feet 6 inches, or setback violations that trigger a variance process can make garage conversion more expensive and slower than new detached construction. We offer free second opinions on any written estimate you’ve already received - if a contractor is pushing garage conversion when detached makes more sense, we’ll tell you straight.
- Your lot has underutilized space that meets ADU setbacks. Many San Bernardino R-1 lots, particularly the larger parcels in the North Park and Del Rosa areas built in the 1950s and 1960s, have 7,000-10,000 square feet with ample rear yard beyond the required setbacks. If that space is currently lawn or storage, it’s generating zero return. A detached ADU converts dead space into income-producing square footage, and California’s ADU law prevents HOAs from blocking construction on single-family lots.
- You’ve received a written estimate that feels vague or incomplete. Estimates that list “TBD” for permits, “allowance” for finishes, or exclude utility trenching are estimates designed to rise. Haven Standard Clause 1 requires a written price before any work starts, and Clause 5 locks the scope at signing. If your current estimate doesn’t meet that standard, call (909) 359-6463 for a free second opinion. We’ll review what you have and show you what a complete, fixed-price proposal looks like.
Our New Detached ADU Process - Step by Step
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Site Survey and Feasibility Analysis. We visit your San Bernardino property with a licensed surveyor and document existing conditions: lot dimensions, slope, utility locations, tree canopy, and any easements or encroachments visible from the public record. You receive a documented photo record of what we found - not a summary of how it felt, but evidence of your soil type, your existing electrical panel capacity, and your sewer lateral condition. This becomes the basis for every line item in your written price.
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Design and Permit Set Production. Our in-house designers produce architectural drawings, structural calculations, Title 24 energy compliance, and the specific San Bernardino building department forms required for plan check submittal. The permit set is our core product, not an afterthought - we’ve been refining this process since 2015, the year California’s ADU laws began their modern evolution. You review the drawings before submission, and revisions are included in the fixed price.
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Plan Check Navigation and Approval. San Bernardino’s building department has specific reviewers, specific checklists, and specific back-and-forth patterns. We know them because we’ve been through them repeatedly. Our project managers track your plan check status weekly, respond to corrections with revised drawings within 48 hours, and escalate when a review exceeds standard timelines. You receive copies of every departmental communication.
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Construction and Inspection Sequence. Whether custom stick-build or prefab/modular installation, our crews work from the approved permit set with zero deviation unless documented in a written change order - which, under Haven Standard Clause 5, requires your signature and a revised price before proceeding. Every site visit generates a documented photo record: what was completed, what conditions were encountered, what decisions were made. You see your project progress in real time, not at the final walkthrough.
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Final Inspection, Certificate of Occupancy, and 365-Day Done Right Promise. We coordinate the final inspection sequence, correct any punch-list items immediately, and deliver your certificate of occupancy. Then the 365-Day Done Right Promise begins: if anything in the finished ADU is not built to the permitted drawings, we make it right. This isn’t a verbal assurance - it’s in writing, before the project starts, backed by the documented photo record that proves what was built.
How Much Does New Detached ADU Cost in San Bernardino?
A typical custom built detached ADU in San Bernardino runs $220,000-$350,000 all-in, from site survey through final inspection, for a studio or 1-bedroom unit of 400-600 square feet with mid-grade finishes, per our New Detached ADU cost guide. Prefab and modular systems from Abodu or Cover typically range $180,000-$280,000 for comparable size, with the factory efficiency offsetting some of the site-specific costs, though crane access and foundation work can narrow that gap on difficult lots. A 2-bedroom custom unit pushing 1,000-1,200 square feet with upgraded finishes typically runs $350,000-$450,000 in San Bernardino’s current market.
| ADU Type | Size Range | Typical All-In Cost in San Bernardino |
|---|---|---|
| Studio ADU (custom) | 300-450 sq ft | $220,000-$280,000 |
| Studio ADU (prefab/modular) | 300-450 sq ft | $180,000-$240,000 |
| 1-Bed ADU (custom) | 500-700 sq ft | $260,000-$350,000 |
| 1-Bed ADU (prefab/modular) | 500-700 sq ft | $220,000-$290,000 |
| 2-Bed ADU (custom) | 800-1,200 sq ft | $350,000-$450,000 |
| 2-Bed ADU (prefab/modular) | 800-1,200 sq ft | $300,000-$380,000 |
What moves your project within or above these ranges: soil conditions requiring engineered foundations (common in the hillside areas near Highland and Redlands), utility upgrades when your existing electrical service is 100 amps or your sewer lateral is original clay pipe, finish selections that push beyond mid-grade, and site access limitations that require specialized equipment. What doesn’t move the price: our fee. The written price is fixed at signing under Haven Standard Clause 5. No door-side upsells, no “we found a problem” surprises without documentation and your written approval of a revised price.
To avoid overpaying, get at least one written estimate that includes every phase - design, permits, construction, utility connections, and final inspection - not a low base price with allowances that inflate. Compare the documentation each provider offers: do you receive a permit set you can review, a photo record of every visit, and a written warranty? These aren’t extras; they’re the minimum standard for a six-figure construction decision. Call (909) 359-6463 for your free estimate. If you already have a written estimate in hand, we’ll provide a free second opinion.
New Detached ADU Near San Bernardino - Our Service Area
Ellery ADU Studio serves San Bernardino and the surrounding Inland Empire cities where homeowners face similar zoning opportunities and construction conditions. Our typical project radius includes New Detached ADU in Rialto, New Detached ADU in Colton, Grand Terrace, Highland, Redlands, Fontana, Riverside, Rancho Cucamonga, Moreno Valley, Yucaipa, and Hesperia. Response time for initial site surveys is typically 3-5 business days in San Bernardino proper, with slightly longer lead times for the outer reaches of our service area. The permit process varies by jurisdiction - Riverside County’s unincorporated areas have different checklists than San Bernardino city, and Fontana’s plan check timeline runs longer - but our project managers know each municipality’s specific requirements because we’ve worked in all of them since 2015.
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.
Frequently Asked Questions - New Detached ADU in San Bernardino
A new detached ADU is a separate, self-contained dwelling unit built from the ground up on your property, not attached to your main house or converted from existing space. It has its own foundation, walls, roof, kitchen, bathroom, and utility connections, and it’s subject to California’s ADU law and your local city’s zoning requirements. In San Bernardino, detached ADUs are permitted on most single-family lots up to 1,200 square feet, provided you meet setback, height, and parking rules. Call (909) 359-6463 for a free estimate on your specific lot.
A typical new detached ADU in San Bernardino takes 8-14 months from contract signing to certificate of occupancy, with custom builds running longer than prefab or modular installations. Design and permit set production takes 6-10 weeks, San Bernardino’s plan check typically runs 8-12 weeks for a complete submittal, and construction ranges from 4-8 months depending on size, complexity, and weather. Prefab and modular systems can compress the construction phase by 30-50% because factory production runs parallel to site preparation. Your written proposal includes a timeline specific to your project type and site conditions.
A new detached ADU in San Bernardino typically costs $180,000-$450,000 all-in, depending on whether you choose prefab/modular or custom construction, the unit size, and your finish selections. A studio prefab unit from Abodu or Cover typically starts near $180,000-$240,000, while a custom 2-bedroom build with upgraded finishes can reach $350,000-$450,000. Every project receives a written price before any work begins, per Haven Standard Clause 1, with no change orders unless you approve a documented scope revision in writing. Call (909) 359-6463 for an exact quote on your lot - estimates are free.
Yes, we specify and coordinate both Abodu and Cover prefab systems in San Bernardino, with direct experience navigating their factory coordination, delivery logistics, and local code compliance. We’ve completed Abodu installations in San Bernardino County’s inland climate zone and understand the crane access, foundation tolerances, and utility connection sequences these systems require. Both brands are integrated into our single-contract model - design, factory coordination, site prep, and final inspection under one written price. If you’re comparing prefab options, we’ll walk you through the specific fit for your lot conditions.
ADU construction is planned work, not emergency service, so we don’t promise same-day dispatch or overnight response for new detached ADU projects. What we do offer is a live person answering calls 24/7 - no voicemail queue, no callback promise that doesn’t materialize - so you can reach us evenings and weekends to discuss timeline, review your estimate, or address concerns that arise during construction. For genuine emergencies like storm damage or structural failure at an existing property, we can assess whether our scope covers the situation or refer you to an appropriate specialist.
We offer the 365-Day Done Right Promise: if the finished ADU is not built to the permitted drawings, Ellery ADU Studio makes it right, in writing, before the project starts. This is backed by the documented photo record from every site visit, which proves what was built and when. Beyond our promise, standard California construction warranty law applies to materials and workmanship. We don’t hide behind minimum legal requirements - we document everything so there’s no dispute about what was promised versus what was delivered.
Gather your property’s assessor parcel number, any existing survey or plot plan you received at purchase, and your current utility bills showing electrical and water service levels. If you have a written estimate from another provider, bring it - we offer a free second opinion and will show you what’s complete, what’s missing, and where the risk of cost escalation lies. We’ll handle the rest: the site survey, the feasibility analysis against San Bernardino’s zoning code, and the written price proposal. Call (909) 359-6463 to schedule - no preparation is required beyond what you already have.
Schedule Your New Detached ADU Service in San Bernardino Today
Call (909) 359-6463 to schedule your free estimate. A live person answers 24/7, and you’ll receive a written price before any work begins - per Haven Standard Clause 1, always, on every project. If you already have a written estimate in hand, ask for our free second opinion. We’ll show you what a complete, fixed-price, single-contract ADU proposal looks like, with a documented photo record on every visit and a 365-Day Done Right Promise in writing. Nadia Ellery has led Ellery ADU Studio since 2015, and our team has designed, permitted, and built over 900 ADUs across San Bernardino and the Inland Empire. Your lot, your timeline, your written price - that’s the standard we work to.
Written by Nadia Ellery, Owner at Ellery ADU Studio, serving San Bernardino since 2015.