New Detached ADU in West Hills - One Fixed Price, Permits Handled

Fast, Reliable New Detached ADU Across West Hills

A new detached ADU in West Hills typically runs $220,000-$420,000 all-in, from the first site measurement through final inspection, depending on whether you build custom or specify a prefab system. We’re Ellery ADU Studio, and our New Detached ADU team serves West Hills from our Los Angeles office, with crews who know the local permit path at the Van Nuys Development Services Center and the added fire department review that most of this area requires. Call (747) 294-4817 to schedule your free estimate. We’ll bring a written price, not a callback promise.

Call (747) 294-4817

Why Ellery ADU Studio Santa Clarita Is West Hills’s Preferred New Detached ADU Company

We’ve designed, permitted, and built ADUs across the San Fernando Valley since 2015, and Garage Conversion ADU - West Hills projects stand apart. The neighborhood’s oversized ranch lots, many stretching past 10,000 square feet off Roscoe Boulevard and Victory Boulevard, make detached backyard cottages genuinely practical in ways they aren’t in denser parts of the valley. But that same acreage sits under a Very High Fire Hazard Severity Zone overlay that adds a fire-resistive plan check most homeowners never anticipate.

Our crews know both sides of that equation. We’ve redrawn permit sets mid-review for ignition-resistant cladding when standard siding came back rejected. We’ve scoped electrical service upgrades and galvanized line replacements on the first visit so permits don’t stall later. And we document every finding with photos, shared with you, so you see what we see.

Under Haven Standard Clause 1, every West Hills project receives a written price before any work begins. No “call for a quote” here. The price you sign is the price you pay. Our 365-Day Done Right Promise, backed in writing, means if the finished ADU doesn’t match the permitted drawings, we make it right.

A live person answers our phones 24/7. No voicemail queue, no callback that doesn’t materialize.

Our New Detached ADU Services in West Hills

Custom Built ADU

Custom builds on West Hills ranch lots give you full control over layout, ceiling height, and exterior finish, but they also expose every local constraint. On a 13,000 square foot ranch lot off Roscoe Boulevard near the Santa Susana Pass edge of West Hills, our crew pulled a detached 1-bed ADU behind a rear shop and hit the VHFHSZ wall mid-plan-check. The original LP SmartSide callout came back rejected, so we redrew around James Hardie ignition-resistant cladding, Class A roofing, and ember-resistant vents, then upgraded a 100-amp panel and tied drainage to a new swale before the lot would hold grade. That project still cleared because we scoped the fire zone, electrical, and grading as a single system from day one. Custom built ADUs in West Hills typically run $280,000-$420,000 all-in.

Prefab ADU Installation

Prefab systems from brands like Plant Prefab and Tuff Shed can compress the construction timeline on West Hills properties, but the fire zone rules don’t bend for factory-built units. The same ignition-resistant exterior assemblies, Class A roofing, and ember-resistant vents apply. We specify and coordinate prefab delivery within our single contract, so the factory drawings and the site prep drawings are reviewed together at the Van Nuys permit counter. Prefab ADU installation in West Hills typically runs $220,000-$340,000 all-in, including the fire-resistive upgrades and foundation work that standard prefab quotes often omit.

Modular ADU

Modular construction, including systems from Mighty Buildings and Boxabl, works in West Hills when the module dimensions and crane access are matched to the lot geometry early. Many of these ranch properties have rear access via alleys or secondary driveways off Kittridge Street or Fallbrook Avenue, but others require modules sized for a front-lot crane set. We verify access, setback, and utility tie-in points before quoting. Modular ADUs in West Hills typically run $240,000-$380,000 all-in.

Studio ADU

A studio ADU, 350-450 square feet, is the most common detached unit we permit in West Hills. The smaller footprint keeps the foundation and framing cost contained, but it doesn’t reduce the fire-zone material requirements. Every square foot of exterior still needs ignition-resistant cladding. The payoff is rental income or family housing on a lot that already has the space. Studio ADUs in West Hills typically run $220,000-$300,000 all-in.

1-Bed & 2-Bed ADU

Larger detached units, 500-800 square feet, are where West Hills’s oversized lots really show their advantage. A 2-bedroom ADU with full kitchen and laundry needs more utility capacity, which is where the original 100-amp panels and galvanized supply lines we find on pre-1980 homes become the critical path. We scope the service upgrade and water line replacement in the initial quote so the permit doesn’t stall at plan check. 1-bed ADUs in West Hills typically run $260,000-$340,000; 2-bed units run $320,000-$420,000 all-in.

Trusted Brands We Service in West Hills

We specify and coordinate prefab and modular systems from Mighty Buildings, Boxabl, Plant Prefab, and Tuff Shed, plus James Hardie ignition-resistant cladding for custom and site-built work. Our New Detached ADU in West Hills clients receive factory drawings and material specifications reviewed against local fire-zone requirements before any deposit is taken. We don’t sell you a module and hand you a separate contractor for the foundation. One contract, one written price, one crew accountable for the match between what was permitted and what gets built.

Common New Detached ADU Problems We See in West Hills Homes

• VHFHSZ surprises mid-permit. Homeowners don’t learn their parcel is mapped Very High Fire Hazard Severity Zone until the plan check triggers fire-resistive review. At that point, standard LP SmartSide or vinyl siding is rejected and the design has to be redrawn around ignition-resistant cladding. We check the fire zone map at the first site visit and price the material upgrade into the initial quote.
• Undocumented outbuildings and drainage. Oversized West Hills ranch lots often come with existing rear shops, sheds, and outbuildings whose locations, setbacks, and drainage patterns were never formally documented. A detached ADU pad ends up fighting shed footprints, well and septic clearances, and standing water that pools during winter storms. We survey and photograph the full rear yard before drafting.
• Electrical and plumbing at capacity. Original 100-amp panels and galvanized supply lines are common in the 1955-1980 housing stock. A detached ADU permit can stall unless the service upgrade and water line replacement are scoped and priced up front. We open the main panel and trace the supply line on every first visit.
• Santa Ana wind exposure on backyard structures. West Hills sits where the Santa Susana Pass funnels Santa Ana winds, making ember intrusion a genuine seasonal hazard. The VHFHSZ construction requirements are enforced strictly here for good reason. We specify ember-resistant vents and tight eave details that standard valley contractors sometimes miss.

Pricing for New Detached ADU in West Hills, CA

We Also Serve Cities Near West Hills

Our crews work throughout the west San Fernando Valley, including West Hills and neighboring Canoga Park, Winnetka, Chatsworth, and Porter Ranch. Each city has its own permit path, fire zone mapping, and utility constraints. We adjust the scope and the quote to match the specific property, not the zip code.

FAQs - New Detached ADU in West Hills