Fast, Reliable New Detached ADU Across Claremont
A new detached ADU in Claremont typically runs $280,000-$520,000 all-in, from the first site measure through final inspection, depending on whether you’re building on a standard city lot or an acreage parcel with county permitting. We’re Ellery ADU Studio, and our New Detached ADU team coordinates design, permit set, and construction under one written contract at one written price. Dispatch and scheduling run from our Los Angeles office, but our crews serve Claremont directly - from the Craftsman bungalows near the Colleges to the ranch homes south of Foothill Boulevard. Call (909) 506-1121 to schedule your free estimate.
Why Ellery ADU Studio Rancho Cucamonga Is Claremont’s Preferred New Detached ADU Company
We’ve designed, permitted, and built ADUs in Claremont since the 2015 state law changes opened the market, and our permit sets here reflect what the city actually enforces - not what a template guesses. Our 365-Day Done Right Promise applies to every Claremont project: if the finished ADU doesn’t match the permitted drawings, we make it right, in writing, before we start.
Claremont homeowners receive a documented photo record on every site visit - evidence of what we found, not a summary of how it felt. That matters here, where heritage trees and fire-zone detailing create inspection points that less experienced teams miss.
Under Haven Standard Clause 1, every Claremont project gets a written price before any work begins. No “call for pricing.” No range that widens later. We’ve completed 900+ ADUs since 2015, every one with that written price and photo record.
A live person answers our phones 24/7. If you’re comparing estimates, we offer a Free Second Opinion on any written quote already in hand.
Our New Detached ADU Services in Claremont
Custom Built ADU
Our custom built ADUs in Claremont are designed from slab to roof to match your lot’s specific constraints - and Claremont has more of those than most cities. On a deep lot off College Avenue near the Claremont Colleges, our crew scoped a 1-bed detached ADU behind a 1920s Craftsman bungalow and deliberately shifted the slab six feet east to clear a protected elm’s dripline before we ever submitted to the county. We built with James Hardie ignition-resistant siding and ember-resistant vents because that parcel sits in a Chapter 7A review zone, and we swapped the water heater to a descaling-friendly model to survive Claremont’s mineral-heavy Pomona Valley water. Custom means we spec for your actual conditions, not a generic plan.
Prefab ADU Installation
We specify and coordinate prefab systems from Mighty Buildings, Plant Prefab, and Tuff Shed within our single-contract model - the designer and installer are the same entity, so there’s no gap between what was drawn and what arrives on the truck. In Claremont, prefab works best on lots with clear crane access and no heritage-tree conflicts in the delivery path. We verify both before quoting. The Haven Standard written price covers transport, set, utility tie-in, and finish - not just the module.
Modular ADU
Modular construction in Claremont follows the same code path as site-built, but with factory-controlled quality and faster weather-independent production. We coordinate modular brands including Boxabl and Dvele for clients who need speed without sacrificing inspection readiness. On northern Claremont parcels in the High Fire Hazard Severity Zone, we specify factory-applied ignition-resistant exteriors that meet CAL FIRE Chapter 7A - documented in the permit set, not added later.
Studio ADU & 1-Bed & 2-Bed ADU
Studio ADUs suit Claremont’s college-town rental market - faculty and graduate students from the Claremont Colleges pay reliably and stay longer than typical tenants. A studio detached ADU in Claremont typically runs $280,000-$360,000. Our 1-bed units, popular with research staff and visiting professors, run $340,000-$440,000. Two-bedroom detached ADUs, which work for small families or dual-income roommates, range $420,000-$520,000. Each price is written and locked at signing per Haven Standard Clause 5 (No Surprises).
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.
Before
AfterTrusted Brands We Service in Claremont
We specify and coordinate prefab and modular systems from Mighty Buildings, Boxabl, Plant Prefab, Tuff Shed, and James Hardie - all within our single-contract design-build model. For Claremont’s High Fire Hazard Severity Zone parcels, we default to James Hardie fiber-cement siding and specified ember-resistant venting that satisfies CAL FIRE Chapter 7A without last-minute substitutions. Our crews carry these specifications in the field, so the installed product matches the permit set. No chasing down a separate installer who “hasn’t seen the drawings.”
Common New Detached ADU Problems We See in Claremont Homes
- Footprint set inside a protected tree’s dripline. Claremont’s heritage tree ordinance treats mature specimens - including the American elms lining College Avenue - as near-untouchable. A permitted ADU whose foundation clips a protected dripline can be forced into arborist review and redesign after plan check approval. We pull a tree survey before locking the slab location.
- Missing CAL FIRE Chapter 7A ignition-resistant detailing. Northern Claremont parcels fall in a High Fire Hazard Severity Zone. ADUs here need ember-resistant vents, ignition-resistant siding, and specific eave detailing. We scope these as line items, not surprises.
- Scoping a county-permitted rural parcel like an in-city lot. Acreage around Claremont means county rather than city permitting, with septic setbacks, well clearances, long material hauls, and open-lot grading and drainage. Each adds scope we quantify before quoting.
- Ignoring Claremont’s mineral-heavy water. The Pomona Valley’s hard water accelerates scale buildup. We spec descaling-friendly water heaters and appropriate fixtures so the ADU’s mechanical systems last.
Pricing for New Detached ADU in Claremont, CA
A new detached ADU in Claremont runs $280,000-$520,000 all-in, with the final figure driven by four factors we scope before you sign. First: lot type. Standard city lots with city permitting and municipal utilities sit at the lower end. County-permitted acreage parcels with septic, well, and extended utility runs push toward the upper range. Second: fire zone. Parcels in northern Claremont’s High Fire Hazard Severity Zone add CAL FIRE Chapter 7A materials and detailing - typically $15,000-$30,000. Third: tree constraints. Heritage-tree dripline conflicts requiring redesign or arborist review add survey and revision costs we disclose upfront. Fourth: unit size and finish level. Studio units start around $280,000; 2-bed units with upgraded finishes reach $520,000.
Every figure above is a written price before work starts, per Haven Standard Clause 1. Call (909) 506-1121 for your exact quote - estimates are free.
We Also Serve Cities Near Claremont
Our crews build throughout the Pomona Valley. We also serve Claremont neighbors in Montclair, La Verne, Upland, and Ontario - each with its own permitting quirks, water conditions, and fire-zone boundaries that we account for in the permit set.
Serving Claremont, CA - Our Local Coverage Area
We’re based in the Claremont 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 Claremont
Yes, if your lot has mature trees. Claremont’s heritage tree ordinance can force redesign after plan check if a protected tree’s dripline overlaps your foundation. We pull the tree survey before locking the slab location, not after. Call (909) 506-1121 to schedule a site review - estimates are free.
Parcels in northern Claremont’s High Fire Hazard Severity Zone require Chapter 7A detailing - ember-resistant vents, ignition-resistant siding, and specific eave construction. We verify your parcel’s fire zone in the first site review and spec the materials into your written quote. Call (909) 506-1121 to check your address.
Claremont’s mineral-heavy Pomona Valley water accelerates scale buildup in water heaters and fixtures. We spec descaling-friendly mechanicals and appropriate fixtures so your ADU’s systems last. This is a line item in our written scope, not an afterthought. Call (909) 506-1121 for a quote that includes it.
Acreage parcels outside Claremont city limits fall to county permitting, with separate septic setbacks, well clearances, and grading requirements. We scope these as distinct line items - longer material hauls, open-lot drainage, equipment access - before quoting. Call (909) 506-1121 to clarify your parcel’s jurisdiction.
Open acreage adds county permitting, septic and well setbacks, extended utility trenching, grading and drainage design, and longer material delivery. Each is a quantified line item in our written quote. Standard backyard city-lot ADUs avoid these costs but may face stricter setback and coverage rules. Call (909) 506-1121 for a scope matched to your actual lot.
Written by Nadia Ellery, Owner at Ellery ADU Studio, serving Claremont and the Pomona Valley since 2015.