Fast, Reliable New Detached ADU Across Calabasas
A new detached ADU in Calabasas typically costs $320,000-$580,000 all-in, from permit-ready drawings through final inspection, with most projects taking 14-22 months including the dual-track city and HOA approvals that define this market. We coordinate design, permitting, and construction from our Los Angeles office, with crews serving Calabasas properties directly - no subcontractor handoffs, no designer-versus-builder blame gap. Call (805) 301-9518 to schedule your free estimate, or bring us any written estimate already in hand for a Free Second Opinion.
Why Ellery ADU Studio Camarillo Is Calabasas’s Preferred New Detached ADU Company
We’ve designed, permitted, and built ADUs across Calabasas since 2015 - the year California’s ADU laws shifted - and our 900+ completed projects include dozens in The Oaks, The Classics, and Calabasas Highlands. Our Calabasas clients receive the same documentation we provide everywhere: a written price before any work starts (Haven Standard, Clause 1), a documented photo record on every site visit, and a 365-Day Done Right Promise backed in writing.
Dispatch and scheduling are coordinated from our Los Angeles office, with construction crews assigned to Calabasas projects locally. That matters when you’re sequencing foundation work around an HOA design committee’s color sign-off - you need a team that can pivot the calendar without losing the permit window. Nadia Ellery, our founder, reviews every Calabasas permit set personally before it hits the city or the HOA.
Our license number appears on every page. Our crews are background-checked and uniformed. And a live person answers calls 24/7 - no voicemail queue, no callback that doesn’t materialize.
Our New Detached ADU Services in Calabasas
Custom Built ADU
Custom built ADUs in Calabasas run $380,000-$580,000 all-in, drawings through final inspection. This is the right path when your HOA design review committee demands roofline, material, and color-palette matches that off-the-shelf products can’t hit. In The Oaks, for example, we re-detailed a standing-seam metal roof to Spanish tile and a James Hardie stucco envelope to satisfy the committee - then sequenced the foundation package to release independently so the build didn’t stall waiting on final color sign-off. Every custom project gets a permit set as the core deliverable, not an afterthought.
Prefab ADU Installation
Prefab ADU installation in Calabasas typically ranges $320,000-$460,000, but with a critical caveat: your prefab system must clear both City of Calabasas planning and your HOA design review committee. We specify and coordinate Abodu, Cover, and other prefab brands within our single-contract model, and we front-load the HOA submittal so the manufacturer’s standard exterior package doesn’t get rejected mid-process. Not every prefab product can adapt to Calabasas’s Chapter 7A fire-hardening requirements or the aesthetic constraints of gated communities. We’ll tell you straight if prefab makes sense for your specific HOA.
Modular ADU
Modular ADUs in Calabasas fall in the $340,000-$480,000 range and share the same dual-track approval reality as prefab. The difference is in the building code: modular units are permitted as real property, not vehicles, which can simplify financing but complicates the HOA review if the manufacturer’s standard cladding doesn’t match your community’s palette. We coordinate modular systems from brands including Dvele and Mighty Buildings, and we build the HOA submittal into the factory order timeline so you’re not paying for site prep while the module sits in queue.
Studio ADU & 1-Bed & 2-Bed ADU
Studio ADUs in Calabasas start around $320,000; 1-bed units run $350,000-$480,000; 2-bed units range $420,000-$580,000. The bed count drives foundation and utility scope more than footprint alone. On hillside parcels along Mulholland or upper Las Virgenes, a 2-bed ADU often triggers caisson piers and engineered retaining walls that a studio on flat ground avoids. We size the unit to your lot’s buildable envelope and your HOA’s height restrictions, not the other way around. Every configuration gets a written price before work starts, per Haven Standard Clause 1.
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.
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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 Coordinate in Calabasas
We specify and coordinate prefab and modular systems from Abodu, Cover, Tuff Shed, and James Hardie within our single-contract design-build model. In Calabasas, brand selection is rarely about the product alone - it’s about whether the exterior package can be adapted to satisfy your HOA’s roofline, material, and color-palette requirements while still meeting Chapter 7A fire-hardening standards. We front-load that analysis so you’re not redesigning after the HOA committee meets.
Common New Detached ADU Problems We See in Calabasas Homes
- Dual-track approval failure: Homeowners submit architectural plans to the City of Calabasas planning department without simultaneously running them through their HOA design review committee. Roofline, exterior material, or color palette mismatches force redesigns and add months. We file both tracks in parallel.
- Chapter 7A non-compliance: Specifying materials that meet California building code but fail fire-hardening standards - standard vents, single-pane windows, non-ignition-resistant siding - triggers plan-check rejections in this Very High Fire Hazard Severity Zone. We design to 7A from the first drawing.
- Septic system surprises: On canyon-adjacent or hillside parcels, particularly along the Mulholland corridor and upper Las Virgenes Road, homeowners often discover mid-project that their existing septic system must be load-tested and frequently replaced or expanded before the city will issue a permit. That’s a $25,000-$40,000 line item we flag during initial site analysis, not at plan check.
- Grading and foundation underestimation: Calabasas’s 1980s-2000s hillside homes sit on parcels with significant grade changes. Sloped terrain frequently triggers grading permits, engineered retaining walls, and caisson or pier foundations that flat-ground estimates don’t capture. Our site analysis includes a preliminary geotechnical assessment.
Pricing for New Detached ADU in Calabasas, CA
| ADU Type | Typical Range (All-In) | What Drives the Top of Range |
|---|---|---|
| Studio ADU | $320,000-$420,000 | Hillside foundation, septic replacement |
| 1-Bed ADU | $350,000-$480,000 | Retaining walls, HOA-mandated materials |
| 2-Bed ADU | $420,000-$580,000 | Caisson piers, dual-track approval delays |
| Custom Built ADU | $380,000-$580,000 | Architectural complexity, fire-hardening upgrades |
| Prefab/Modular ADU | $320,000-$480,000 | HOA adaptation, factory timeline coordination |
These ranges reflect what we’ve actually quoted and built in Calabasas. The top of each range typically involves hillside foundations, septic system replacement, or HOA-mandated material upgrades that standard estimates don’t include. Under Haven Standard Clause 1, every project gets a written price before any work begins - no “call for a quote,” no open-ended allowances. We also offer a Free Second Opinion on any written estimate already in hand. Call (805) 301-9518 for your specific quote; estimates are free.
We Also Serve Cities Near Calabasas
Our New Detached ADU in Calabasas crews also work in West Hills, Topanga, Canoga Park, and Agoura Hills. Each city carries its own approval timeline and building constraints, but our single-contract model and documented permit-set process apply across the region. If you’re comparing properties across these markets, we can quote the same ADU program for multiple sites so you understand how local conditions affect your all-in cost.
Serving Calabasas, CA - Our Local Coverage Area
We’re based in the Calabasas 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 Calabasas
Yes. While AB 670 (2020) prohibits HOAs from banning ADUs outright, Calabasas associations - including The Oaks, The Classics, and Calabasas Highlands - retain authority to enforce architectural design standards on roofline, exterior materials, and color palette. Your project must clear both the City of Calabasas planning department and your HOA design review committee before construction begins. We file both tracks simultaneously and build the committee’s typical feedback into our initial submittal to avoid redesign delays. Call (805) 301-9518 to discuss your specific HOA’s requirements.
Three factors: dual-track HOA approval adds design and timeline costs; Cal Fire’s Very High Fire Hazard Severity Zone classification mandates Chapter 7A fire-hardening materials (ember-resistant vents, ignition-resistant siding, multi-pane windows) that coastal LA communities 15 miles west don’t require; and hillside parcels frequently need engineered foundations, retaining walls, and septic system upgrades. A comparable studio ADU in Santa Monica might run $280,000-$360,000; in Calabasas, the same program is typically $320,000-$420,000. We itemize these deltas in every written quote.
Parcels along the Mulholland corridor and upper Las Virgenes Road often rely on private septic systems rather than Las Virgenes Municipal Water District sewer. The City of Calabasas will require a load test of your existing system during plan check, and most 1980s-2000s systems cannot handle the additional bedroom count of a new ADU. Replacement or expansion typically runs $25,000-$40,000 and must be permitted before your ADU permit issues. We flag this during initial site analysis and include it in your written price, not as a surprise change order. Call (805) 301-9518 to schedule a site evaluation.
The dual-track city-plus-HOA approval typically adds 4-8 months compared to cities without HOA review. City of Calabasas planning review runs 3-4 months for a complete submittal; HOA design review committees meet quarterly or monthly and often require one revision cycle. We sequence construction packages - particularly the foundation and rough plumbing - to release independently of final HOA color sign-off so the build doesn’t stall with exposed work-in-place. Most Calabasas detached ADUs move from signed contract to certificate of occupancy in 14-22 months.
Yes. Much of Calabasas’s housing stock sits on hillside parcels with significant grade changes. Sloped terrain frequently triggers grading permits, engineered retaining walls, and caisson or pier foundations rather than standard slab-on-grade construction. In The Oaks project we referenced, the slope required caisson piers and an engineered retaining wall that added roughly $45,000 to the foundation package compared to flat-ground construction. Our site analysis includes preliminary geotechnical assessment so these costs appear in your written price, not as mid-project surprises. Call (805) 301-9518 to schedule your evaluation.
Ready to price your detached ADU? Call (805) 301-9518 to schedule your free estimate. Bring any written estimate you already have - we’ll provide a Free Second Opinion, line by line, under Haven Standard Clause 1’s written-price guarantee.
Written by Nadia Ellery, Owner at Ellery ADU Studio, serving Calabasas since 2015.