Fast, Reliable New Detached ADU Across Highland
A new detached ADU in Highland typically runs $185,000-$340,000 all-in, from the first site survey through final inspection, with the final number driven by whether your lot falls north or south of Base Line Street. We’re Nadia Ellery’s team at Ellery ADU Studio, and we coordinate design, permitting, and construction from our Inland Empire office for Highland homeowners specifically - including Garage Conversion ADU - Highland projects. If you’re on a 1970s-1990s tract lot with original wiring and a generous backyard, you’re in the exact housing stock we work most.
Call (909) 359-6463 to schedule your free estimate. Every project gets a written price before any work starts, per Haven Standard Clause 1.
Why Ellery ADU Studio San Bernardino Is Highland’s Preferred New Detached ADU Company
We’ve designed, permitted, and built more than 900 ADUs since 2015, the year California’s ADU laws shifted, and a significant share of those have been in Highland and the surrounding San Bernardino Valley. Our New Detached ADU in Highland work is governed by The Haven Standard: written price locked at signing, documented photo record on every visit, and our 365-Day Done Right Promise backed in writing before the project starts.
Highland homeowners call us back because we flag the two local landmines early: the Very High Fire Hazard Severity Zone boundary that triggers Chapter 7A requirements north of Base Line Street, and the original 100-amp panels we find in most pre-1990 tract homes. Catching those at intake, not at plan-check rejection, is what keeps our Highland projects on schedule. Our license number appears on every page, and our crews are background-checked and uniformed. A live person answers calls 24/7.
Our New Detached ADU Services in Highland
Custom Built ADU
A custom built ADU in Highland gives you full control over layout, finishes, and how the structure meets your specific lot conditions. On foothill parcels north of Base Line Street, that means we specify Class A roofing, ember-resistant vents, and ignition-resistant exterior cladding from the first drawing - not as a change order after plan check fails. Custom builds here typically run $220,000-$340,000 all-in, depending on square footage and whether the site needs utility trenching or septic adaptation. We handle the full permit set, the Chapter 7A materials specification if triggered, and the construction under one contract at one written price.
Prefab ADU Installation
Prefab ADU installation in Highland works well on valley-floor lots with straightforward access and standard fire-zone classification. We specify and coordinate systems from Dvele, Mighty Buildings, and Plant Prefab, integrating their factory-built modules with your site prep, foundation, and utility tie-ins under our single contract. On VHFHZ parcels, prefab is still possible, but the exterior assembly must be verified against Chapter 7A before the factory locks the build - a step many coordinators skip. We don’t. Prefab installations in Highland typically run $185,000-$280,000, with faster close-in times on compliant lots.
Modular ADU
Modular ADU construction in Highland uses crane-set factory modules that arrive 80-90% complete, then marry to your foundation and utility stub-ups on site. This method shines on larger lots with clear crane access, common in Highland’s 7,000-10,000+ sq ft suburban tracts. We coordinate Boxabl and Dvele modular systems, but we also verify that the module’s exterior rating matches your parcel’s fire zone before ordering production. Modular projects in Highland generally fall between $195,000-$295,000, with the foundation and site work priced separately in your written scope.
Studio ADU & 1-Bed & 2-Bed ADU
Studio ADUs in Highland suit homeowners who need a compact, efficient dwelling - often for rental income or aging parents - on tighter budgets or tighter buildable footprints. A studio typically runs $185,000-$240,000. Our New Detached ADU team also designs and builds 1-bed and 2-bed configurations, which represent the majority of our Highland detached work. A 1-bed detached ADU generally runs $210,000-$285,000; a 2-bed, $250,000-$340,000. The bedroom count affects Title 24 energy calculations, HVAC load sizing, and whether the original electrical service can carry the new load without an upgrade - a line item we identify at intake, not after walls are open.
What happens when you call
- 1
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 Highland
We specify and coordinate prefab and modular systems from Dvele, Mighty Buildings, Boxabl, and Plant Prefab, integrating their factory assemblies into our single-contract design-build workflow. For Highland homeowners, this means we handle brand-specific lead times, Chapter 7A compliance verification, and site adaptation - not the homeowner, not a separate contractor. We also work with James Hardie cladding systems when custom builds require ignition-resistant exterior assemblies for foothill-zone compliance. Parts and material specifications are locked at contract signing; no substitution surprises at delivery.
Common New Detached ADU Problems We See in Highland Homes
- The VHFHZ boundary surprise. A permit-ready plan drafted for a valley-floor parcel passes plan check, but the same design on a lot one street north of Base Line Street fails Chapter 7A review. We verify fire zone classification at intake, before the first drawing hour is billed.
- Original 100-amp panels that can’t carry a new dwelling unit. Highland’s 1970s-1990s tract homes often still have their original service. We identify required electrical upgrades during site survey, with the cost written into your upfront quote - not discovered after construction starts.
- Outdated wiring and failed waterproofing revealed only after walls open. Our crew opened the walls of a late-1970s tract home north of Base Line Street to tie in a 1-bed detached ADU and found the original 100-amp panel feeding cloth-jacketed branch wiring, plus a rear patio slab that had been poured over the old hose bib with no vapor barrier. We upgraded the service, replaced the branch circuits before the ADU feeder was pulled, and revised the exterior assembly to Class A roofing and ember-resistant vents so the plan cleared the Chapter 7A review the same client’s neighbor one street downhill never needed.
- HVAC undersized for Highland’s thermal swing. Summer highs above 105°F and winter hard freezes in the foothills mean Title 24 compliance here is stricter than coastal jurisdictions. We run proper load calculations from the permit stage, not guess at tonnage after the walls are closed.
Pricing for New Detached ADU in Highland, CA
Here’s what new detached ADU projects typically cost in Highland’s current market:
| Project Type | Typical Range (All-In) |
|---|---|
| Studio ADU | $185,000 - $240,000 |
| 1-Bed ADU | $210,000 - $285,000 |
| 2-Bed ADU | $250,000 - $340,000 |
| Custom Built ADU (high-end finish, complex site) | $280,000 - $340,000 |
| Prefab/Modular ADU (standard site, valley floor) | $185,000 - $295,000 |
| Electrical service upgrade (100A to 200A) | $4,500 - $8,500 |
| Chapter 7A materials upgrade (VHFHZ parcels) | $8,000 - $18,000 |
Two factors move Highland quotes more than anything else: whether your parcel falls inside the VHFHZ boundary north of Base Line Street, and whether your home still carries its original 100-amp electrical service. Both are discoverable at intake. Both are written into your upfront price under Haven Standard Clause 1. We do not quote low and amend later. Call (909) 359-6463 for your written estimate - it’s free, and it includes the site survey, fire-zone verification, and electrical load check.
We Also Serve Cities Near Highland
Our crews work throughout the Inland Empire, with regular projects in Highland, San Bernardino, Redlands, Colton, and Grand Terrace. The same single-contract design-build model, the same Haven Standard documentation, and the same written-price guarantee apply across every city we serve.
Serving Highland, CA - Our Local Coverage Area
We’re based in the Highland 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 Highland
Only if your parcel falls within California’s state-designated Very High Fire Hazard Severity Zone, which in Highland generally means lots north of Base Line Street and those pressing against the San Bernardino National Forest foothills. We verify your parcel’s fire zone classification during the free site survey, before any design hours are committed. If Chapter 7A applies, we specify Class A roofing, ember-resistant vents, and ignition-resistant exterior cladding in the original permit set - not as a redesign after rejection. Call (909) 359-6463 to check your parcel’s status; estimates are free.
Because 1970s-1990s tract homes in Highland often conceal cloth-jacketed wiring, undersized framing, or failed waterproofing at old patio slabs that isn’t visible until walls open. Our field vignette: a late-1970s home north of Base Line Street revealed original 100-amp service feeding outdated branch circuits and a slab poured directly over a hose bib with no vapor barrier. We handle this by writing inspection allowances into every contract, documenting conditions with photos before and after opening, and pricing any necessary remediation in writing before work proceeds - per Haven Standard Clause 5 (No Surprises). Call (909) 359-6463 to review how we structure allowances for your specific home.
Yes, but the factory’s standard exterior assembly must be verified against Chapter 7A requirements before production locks. We coordinate Dvele, Mighty Buildings, and Boxabl systems specifically, and we hold the factory to the fire-zone spec during the pre-production submittal. The module itself doesn’t change; the exterior finish, venting, and roofing details do. This verification step adds 2-3 weeks to pre-construction but prevents a much costlier field modification or plan-check rejection. Call (909) 359-6463 to discuss whether your foothill lot suits prefab or modular delivery.
Most Highland lots at 7,000-10,000+ sq ft can accommodate a detached ADU up to 1,200 square feet under state law, provided setback and floor-area-ratio requirements are met. The actual buildable footprint depends on your specific lot coverage, existing structures, and whether hillside grading is required for foothill parcels. We measure and model this during the free site survey, producing a buildable envelope map before design begins. Call (909) 359-6463 to schedule the survey and see your specific constraints.
We do quote it upfront - that’s Haven Standard Clause 1. A typical detached ADU in Highland runs $185,000-$340,000 all-in, with the exact figure determined by three things we verify before quoting: your parcel’s fire zone classification, your electrical service capacity, and your chosen bedroom count and finish level. We do not quote ranges without committing to a written price; once we complete the site survey, you receive a line-item written quote with no open-ended allowances. Call (909) 359-6463 to start that process - the estimate is free, and the price you receive is the price you pay.
Ready to build? Call (909) 359-6463 to schedule your free estimate. Nadia Ellery’s team will verify your fire zone, check your electrical service, and deliver a written, line-item price before any work begins - guaranteed under The Haven Standard.
Written by Nadia Ellery, Owner at Ellery ADU Studio, serving Highland and the Inland Empire since 2015.