Fast, Reliable New Detached ADU Across Stevenson Ranch
A new detached ADU in Stevenson Ranch typically runs $285,000-$420,000 all-in, from the permit set through final County inspection, with most projects taking 8-14 months from signed contract to certificate of occupancy. We’re Ellery ADU Studio Lancaster, and our New Detached ADU team has designed, permitted, and built 900+ ADUs since 2015 - the year California’s ADU laws shifted. We serve Stevenson Ranch from our Los Angeles office, with crews who know the Santa Clarita Valley’s unincorporated County process, its HOA layers, and its fire-hazard construction rules. Call (661) 528-5298 to schedule your free estimate.
Why Ellery ADU Studio Lancaster Is Stevenson Ranch’s Preferred New Detached ADU Company
We don’t guess at Stevenson Ranch permits. Every detached ADU here runs through LA County’s Department of Regional Planning and Building & Safety, not Santa Clarita City Hall, and most tracts layer an HOA architectural review on top. Our permit sets are built for that two-track reality from the first drawing.
Our clients in Stevenson Ranch receive a written price before any work starts, per Haven Standard Clause 1. No “call for a quote” - the number is on the page, or it’s in your written estimate after we walk the lot and pull the recorded parcel map.
Our crews are background-checked, uniformed, and licensed. Our license number appears on every page. Every visit produces a documented photo record - you see what we found, not a summary of how it felt.
Calls to (661) 528-5298 reach a live person 24/7. No voicemail queue. No callback that doesn’t materialize.
Our New Detached ADU Services in Stevenson Ranch
Custom Built ADU
A custom built detached ADU in Stevenson Ranch gives you full control over layout, materials, and roofline - critical when your HOA architectural review committee demands design compatibility with the main tract home. We handle the full permit set for LA County Building & Safety, including Chapter 7A ignition-resistant construction details that the County will flag if they’re missing. Custom builds here typically run $320,000-$420,000, depending on square footage, utility trench length, and whether we need to grade a rear pad on sloped lots near Pico Canyon or Southern Oaks Drive.
Prefab ADU Installation
Prefab ADU installation in Stevenson Ranch works well on flatter lots with clear equipment access. We specify and coordinate systems from Abodu, Cover, and Mighty Buildings - all under the same single contract as our custom builds. The catch in Stevenson Ranch is delivery: many driveways in the master-planned tracts were built to standard residential radius, and a 14-foot-wide modular unit on a flatbed needs more turning room than a typical FedEx truck. We survey access before quoting. Prefab detached units typically run $285,000-$360,000 installed, including the County permit set and Chapter 7A upgrades.
Modular ADU
Modular ADU construction in Stevenson Ranch means factory-built modules craned onto a site-built foundation. We coordinate with Dvele and other modular partners, but we keep the permit set and site prep in-house so nothing falls between designer and builder. On Stevenson Ranch lots that back to HOA open space or slope easements, the module placement is constrained before the first drawing - we pull the recorded parcel map and easement documents before we spec the foundation. Modular detached ADUs here typically start around $310,000 and run to $390,000 depending on module count and crane access.
Studio ADU
A studio detached ADU in Stevenson Ranch - 300 to 450 square feet - is the most common size we permit on constrained lots, especially in tracts where the rear yard is narrowed by HOA slope easements. These units work as rental income, home offices, or guest quarters. Because they’re small, every square foot gets engineered: we spec mini-split HVAC, tankless water heaters, and compact kitchen packages that meet LA County’s energy code without wasting footprint. Studio detached units in Stevenson Ranch typically run $285,000-$340,000 all-in.
1-Bed & 2-Bed ADU
One-bedroom and two-bedroom detached ADUs in Stevenson Ranch start at 450 square feet and run to 1,000 square feet, the maximum allowed under state law for most single-family lots. The 1-bed layout is straightforward; the 2-bed adds a second egress window, larger septic or sewer lateral, and often a longer utility trench from the main house. On County water and sewer, the connection fees are fixed. On septic, we verify leach-field capacity before quoting - a step many contractors skip. One-bed detached units typically run $310,000-$370,000; two-bed units run $350,000-$420,000.
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 Stevenson Ranch
We specify and coordinate prefab and modular systems from Abodu, Cover, Dvele, Mighty Buildings, Boxabl, Plant Prefab, Tuff Shed, and James Hardie - all within the same single contract, so neither the designer nor the builder can point at the other when something is off. For Stevenson Ranch’s Chapter 7A fire-hazard requirements, we often default to James Hardie fiber-cement siding with ember-resistant vents and Class A roofing assemblies - materials we know pass LA County plan check on the first submittal. Every brand we specify is documented in the permit set, not swapped after approval.
Common New Detached ADU Problems We See in Stevenson Ranch Homes
- Quoting off the Santa Clarita city checklist instead of LA County forms. Stevenson Ranch is unincorporated County, not City. The applicant wastes a plan-check cycle on forms the County does not accept, and the fire-hazard Chapter 7A details get flagged late - adding 4-8 weeks.
- Missing the slope easement or open-space setback on lots backing to HOA-owned land. Many Stevenson Ranch tracts have rear-lot easements that silently shrink the buildable footprint. A contractor who doesn’t pull the recorded parcel map before quoting often has to downsize or resite the unit after the pad is already cut.
- Treating a detached ADU like an attached garage conversion. Detached units need a separate utility trench, septic or sewer verification, and an equipment-access plan for a delivery truck that cannot clear the driveway radius. These are scope items, not afterthoughts.
- Specifying standard roofing and vents in a Very High Fire Hazard Severity Zone. LA County enforces Chapter 7A on detached ADUs even when the main tract home predates the rule. Ember-resistant vents and non-combustible roofing are not upgrades here - they’re code minimums that add cost and extend plan-check timelines.
Pricing for New Detached ADU in Stevenson Ranch, CA
A new detached ADU in Stevenson Ranch typically runs $285,000-$420,000 all-in, from the initial permit set through final LA County inspection. Here’s how that breaks down by type:
- Studio detached ADU: $285,000-$340,000
- 1-bedroom detached ADU: $310,000-$370,000
- 2-bedroom detached ADU: $350,000-$420,000
- Custom built detached ADU: $320,000-$420,000
- Prefab detached ADU (installed): $285,000-$360,000
- Modular detached ADU: $310,000-$390,000
What moves the number: Chapter 7A fire-hazard materials add 8-12% over standard construction. Grading and drainage on sloped lots near Pico Canyon or Southern Oaks Drive can add $15,000-$40,000. Utility trench length from main house to ADU pad runs $80-$140 per linear foot. Septic system upgrades, when needed, are priced after perc test and leach-field inspection. Every project gets a written price before any work starts, per Haven Standard Clause 1. No change orders, no scope creep. Call (661) 528-5298 for your written estimate - estimates are free.
We Also Serve Cities Near Stevenson Ranch
Our crews work throughout the Santa Clarita Valley and northern San Fernando Valley. We also serve Stevenson Ranch neighbors in Santa Clarita, Castaic, Sylmar, and San Fernando - all under the same single-contract design-build model and the same Haven Standard terms.
Serving Stevenson Ranch, CA - Our Local Coverage Area
We’re based in the Stevenson Ranch 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 Stevenson Ranch
You need an LA County permit, not a Santa Clarita City permit. Stevenson Ranch is unincorporated Los Angeles County, so every detached ADU runs through the County’s Department of Regional Planning and Building & Safety in Valencia. The City of Santa Clarita’s building department has no jurisdiction here. Many contractors assume Santa Clarita rules apply and submit the wrong forms, wasting a plan-check cycle. We pull the correct County checklist before we draw. Call (661) 528-5298 to schedule your free estimate.
It adds Chapter 7A ignition-resistant construction requirements, including ember-resistant vents, non-combustible roofing, and ignition-resistant siding - typically 8-12% to material costs. LA County enforces these on detached ADUs even when the main tract home was built to earlier code. The County plan checker will flag missing Chapter 7A details, so we spec them in the original permit set, not as a late add. Call (661) 528-5298 for a written quote that includes these items upfront.
Often yes, but only after pulling the recorded parcel map and easement documents. Many Stevenson Ranch lots have slope easements or open-space setbacks that shrink the buildable footprint. On a half-acre lot along Southern Oaks Drive near the Pico Canyon trailhead, we set a 600-square-foot detached studio ADU on a graded rear pad that had to clear both an HOA slope easement and the County’s 100-foot brush-clearance line. We pulled the recorded parcel map before quoting, shifted the pad 12 feet east off the easement, and delivered the unit with James Hardie fiber-cement siding and ember-resistant vents. We delivered the load in two trips - a 26-foot box truck could not make the driveway turn - and the unit cleared Building & Safety on the first submittal. Call (661) 528-5298 to walk your lot.
They change it significantly if your tract home is on septic or well water rather than County sewer and water. A detached ADU needs its own service lateral or a verified capacity increase on the existing septic system - we price this after perc test and leach-field inspection, not before. Well water requires a pump and pressure-tank sizing review. The utility trench from main house to ADU pad runs $80-$140 per linear foot in Stevenson Ranch’s rocky soils. These are scope items we verify before quoting, not surprises we discover after excavation. Call (661) 528-5298 for a written estimate that includes these line items.
Driveway radius and rear-lot slope are the two main constraints. Stevenson Ranch’s master-planned tracts were built with standard residential driveway geometry - fine for a Honda, tight for a 14-foot modular unit on a flatbed or a concrete pumper truck. On sloped lots near Pico Canyon, we sometimes need a mini-excavator rather than full-size equipment, which changes the grading timeline. We survey access before quoting and specify equipment in the written scope. No mid-project discovery that the crane won’t fit. Call (661) 528-5298 to schedule your free estimate.
Written by Nadia Ellery, Owner at Ellery ADU Studio Lancaster, serving Stevenson Ranch since 2015.