ADU in West Hills, CA
Junior ADU and interior conversion projects in West Hills typically range from $85,000-$165,000 all-in, while site prep and utility upgrades for any ADU type run $15,000-$55,000 depending on what the 1950s-1970s ranch-era infrastructure needs. We’re Ellery ADU Studio, and we handle both under one contract at one written price - drawings through final inspection - with every West Hills project governed by The Haven Standard. Call (805) 301-9518 to schedule your free estimate.
West Hills presents a distinctive ADU challenge: much of the area sits within a Very High Fire Hazard Severity Zone, where Chapter 7A ignition-resistant construction standards apply. That means ember-resistant vents, fire-rated siding, and multi-pane windows are not upgrades - they’re code requirements that shape every design decision and every line item in your budget.
Why West Hills Homes Are Different
The housing stock in West Hills is overwhelmingly post-WWII single-family ranch homes built from the 1950s through the 1970s. These lots run 8,000-12,000 sq ft, which is generous by San Fernando Valley standards, but the original infrastructure often cannot support an ADU without significant upgrades. We regularly encounter 200-amp electrical panels at capacity, cast-iron sewer laterals past their service life, and original gas lines that the city will not allow us to tie into without replacement.
Closer to the Santa Susana foothills, hillside lots introduce grading, retaining-wall, and expansive-soil challenges that flatland builders in adjacent Canoga Park rarely face. The climate compounds everything: West Hills sits at the western mouth of the San Fernando Valley and catches both extreme summer heat above 100°F and the strongest Santa Ana wind events funneling through the Santa Susana Pass. After the 2018 Woolsey Fire burned through foothills and hillside tracts here, LA updated its VHFHSZ maps and enforcement posture. A West Hills building inspector will specifically look for Chapter 7A compliance documentation - including a fire-rated vent certificate - at rough framing inspection, a check that almost never happens on ADU projects just a few miles east in the flat Valley.
Our Main West Hills Services
These are the three services West Hills homeowners ask about most often. Each has its own dedicated West Hills page with deeper detail.
ADU Design & Permitting in West Hills
Our permit set is the core product, not an afterthought. In West Hills, that means preparing Chapter 7A compliance documentation upfront, before the first inspection, because the VHFHSZ overlay adds a layer of review that flatland ADU projects skip. We handle the full architectural set, structural calculations, Title 24 energy compliance, and all city submittals. ADU Design & Permitting in West Hills covers our full process.
Garage Conversion ADU in West Hills
Garage conversions in West Hills face a specific constraint: if your property is in the VHFHSZ, the converted structure must meet Chapter 7A standards even though the original garage likely does not. That often means re-skinning exterior walls, upgrading windows, and installing ember-resistant vents - costs that don’t appear on flatland garage conversion estimates. We quote these items in writing before work starts. Garage Conversion ADU in West Hills has the full breakdown.
New Detached ADU in West Hills
Detached ADUs on West Hills lots benefit from the generous 8,000-12,000 sq ft typical here, but hillside properties face defensible space setbacks that can constrain placement options. We model multiple siting scenarios against LA’s ADU ordinance and the VHFHSZ overlay to find the buildable envelope before we draw a single wall. New Detached ADU in West Hills explains our approach.
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.
Junior ADU & Interior Conversion in West Hills
Junior ADU and interior conversion work in West Hills solves a specific problem: homeowners who want rental income or multigenerational space but cannot or do not want to build detached. The 1950s-1970s ranch stock here - single-story, often with basements, attached garages, or underutilized wings - is unusually well-suited to this approach. But the same era’s infrastructure means we almost always find electrical, plumbing, or gas limitations that must be resolved before the city will issue a certificate of occupancy. Our Junior ADU & Interior Conversion hub covers our full scope nationwide; what follows is specific to West Hills conditions.
Room-to-ADU Conversion
Signs you need it
You have a 300-500 sq ft wing, sunroom, or former servant’s quarters with separate exterior access and want to legalize it as a rental unit.
What it costs in West Hills
Room-to-ADU conversions in West Hills typically run $85,000-$140,000 all-in, with VHFHSZ properties landing in the upper third due to Chapter 7A window and vent upgrades.
How we do it
We survey existing conditions, produce a permit set that includes Title 24 and Chapter 7A compliance, then build to that set under our single contract with no designer-builder blame gap.
Basement ADU
Signs you need it
Your ranch home has a full or partial basement with ceiling height at or near 7.5 feet and you want to add a legal secondary unit.
What it costs in West Hills
Basement ADUs in West Hills range from $95,000-$165,000, with egress window installation and moisture mitigation driving the lower-range variance and full electrical/plumbing upgrades pushing toward the top.
How we do it
We test for moisture intrusion, design egress and mechanical ventilation to code, upgrade the panel and lateral if needed, and document every visit with a photo record you receive.
What Junior ADU & Interior Conversion Costs in West Hills
| Item | Typical range in West Hills |
|---|---|
| Room-to-ADU conversion | $85,000 - $140,000 |
| Basement ADU | $95,000 - $165,000 |
| Interior JADU (existing bathroom/kitchen) | $75,000 - $125,000 |
Does a Junior ADU need its own meter in West Hills?
No - a Junior ADU shares utilities with the primary residence by definition, though we often recommend a sub-panel upgrade to handle the added load, especially on 1950s-1970s electrical systems common here. Call (805) 301-9518 for an exact quote - estimates are free.
Can I convert my basement if it has moisture issues?
Yes, but only after we specify and install a drainage or vapor-mitigation system that the city inspector will sign off on - we test, document, and warrant that work under our 365-Day Done Right Promise. Call (805) 301-9518 for an exact quote - estimates are free.
ADU Site Prep & Utilities in West Hills
Site prep and utility work in West Hills is where most ADU projects stall before they start. The 1950s-1970s ranch infrastructure here - 200-amp panels at capacity, cast-iron sewer laterals, original gas lines - was never designed for a second dwelling unit, and the city will not issue an ADU permit until these systems are proven adequate or upgraded. Our ADU Site Prep & Utilities hub explains our national approach; the sections below cover what West Hills properties specifically require.
Electrical Panel Upgrade
Signs you need it
Your home has a 200-amp panel with no spare breaker slots, or the main service cable is rated below what an ADU addition demands.
What it costs in West Hills
Electrical panel upgrades in West Hills run $8,500-$18,000, with underground service replacement and trenching through hillside rock at the upper end.
How we do it
We pull the permit, coordinate with LADWP for service disconnect, install the new panel and grounding system, and pass inspection before any ADU construction begins.
Plumbing Lateral
Signs you need it
Your home still has cast-iron sewer lateral or the city requires a larger diameter line to handle the additional fixture units an ADU adds.
What it costs in West Hills
Plumbing lateral replacement in West Hills ranges from $12,000-$28,000, with trenchless methods preferred on established landscaping and full excavation needed where the line has collapsed.
How we do it
We video-inspect the existing line, specify the replacement method in your written scope, pull the permit, and coordinate with LA Sanitation for tie-in approval.
What ADU Site Prep & Utilities Costs in West Hills
| Item | Typical range in West Hills |
|---|---|
| Electrical panel upgrade | $8,500 - $18,000 |
| Plumbing lateral replacement | $12,000 - $28,000 |
| Gas line extension | $4,500 - $12,000 |
Do I need to upgrade my sewer line for a Junior ADU?
Not always - Junior ADUs share the existing sewer lateral, but if the cast-iron line is deteriorated or the city flags it during plan check, replacement becomes a permit condition we handle before construction starts. Call (805) 301-9518 for an exact quote - estimates are free.
Can site prep be done under the same contract as the ADU build?
Yes - that is the entire point of our design-build model; site prep, utilities, and construction are a single contract at a single written price, so neither scope can be orphaned or disputed between separate contractors. Call (805) 301-9518 for an exact quote - estimates are free.
Brands We Service in West Hills
We specify and coordinate prefab and modular systems from Abodu, Cover, and Mighty Buildings within the same single contract that covers your site prep, permitting, and installation. Our Los Angeles office stocks common connection hardware and maintains direct supplier relationships, which keeps lead times predictable and change orders rare. See our brands for the full list.
Pricing for ADU in West Hills, CA
| Service | Typical range in West Hills |
|---|---|
| Room-to-ADU conversion | $85,000 - $140,000 |
| Basement ADU | $95,000 - $165,000 |
| Interior JADU | $75,000 - $125,000 |
| Electrical panel upgrade | $8,500 - $18,000 |
| Plumbing lateral replacement | $12,000 - $28,000 |
| Gas line extension | $4,500 - $12,000 |
| Foundation & grading (hillside) | $15,000 - $45,000 |
| Above-garage ADU | $110,000 - $185,000 |
Prices in West Hills push toward the upper end when Chapter 7A fire-resistant materials are required, when hillside lots need grading or retaining walls, or when the original 1950s-1970s infrastructure needs full replacement rather than extension. Under Haven Standard Clause 1, every project is quoted with a written price before any work begins - no call-for-pricing, no door-side upsells.
Neighborhoods We Serve in West Hills
We work across the full West Hills area, from valley-floor ranch tracts to hillside properties near the Santa Susana foothills. Dispatch and scheduling are coordinated from our Los Angeles office; crews serve West Hills locally with typical first-visit availability within 48 hours of your call.
- West Hills Estates
- Castle Peak
- Hidden Lake
- Three Springs
- Shadow Ranch
Service Area - Cities Near West Hills
Our crews work throughout the western San Fernando Valley and adjacent areas. Homeowners in Canoga Park, CA often face similar flatland conditions with fewer VHFHSZ constraints, while Calabasas, CA and Topanga, CA share West Hills’s hillside and wildfire-exposure challenges. Chatsworth, CA sits immediately north with its own mix of valley-floor and foothill lots. Each city page has local pricing and permit specifics.
Serving West Hills, CA - Our Local Coverage Area
We’re based in the West Hills 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 About ADU in West Hills
LA’s standard ADU timeline is 60-90 days, but West Hills properties in the VHFHSZ add 2-4 weeks for fire department plan check and Chapter 7A compliance verification. We front-load this documentation in our permit set to avoid mid-process delays.
California law prohibits HOAs from outright banning ADUs, but some West Hills associations impose design guidelines or parking requirements that affect your project’s feasibility; we review CC&Rs during our initial site assessment and flag any conflicts before design begins.
Yes - permit application, plan check response, and inspection scheduling are included in our single contract; we do not hand off a permit set and expect you to navigate LA Building & Safety alone.
What happens when you call
- 1A real person answersNo phone trees - talk to a local adu pro.
- 2You get an upfront price rangeHonest numbers before anyone is dispatched. No surprises.
- 3We come out and measureLicensed & insured, at a time that suits you - the visit and the quote are both free.
- 4You get the price in writingLine-itemed, yours to keep, and nothing starts until you say go.
What West Hills Customers Say
"Detached unit in the back garden. Good design, good build quality, and the cost changes were documented and agreed in advance."
- Stefan B."Every allowance was itemised at the start, so the finish selections did not turn into a surprise at the end."
- Benedict H."The permit set and the build were one contract with one number. Our neighbours used two firms and spent a year watching them blame each other."
- Helena V.