Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
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AfterFast, Reliable Home Additions & ADU Across West Hills
Most of the calls we take from West Hills start the same way: a homeowner walked out into the yard, looked at the western hillside, and realized the house just doesn’t fit the way it used to. Maybe the kids are back, or grandma needs to live closer, or the garage is doing nothing but storing boxes. A home addition or ADU in West Hills typically runs $45,000 to $130,000 for a room addition, and $90,000 to $220,000 for a detached ADU, though garage conversions often land between $30,000 and $80,000. Those ranges come from real projects we’ve priced across 91307 and 91308, including the hillside lots along Valley Circle Boulevard and the flatter tracts south of Roscoe.
If you’re weighing whether to add on or build out back, call Tom Barrett’s crew at (877) 610-1318 and we’ll walk the property with you before you commit to anything. Free estimate, no trip charge inside the county.
Why Barrett & Sons Construction Is West Hills’s Preferred Home Additions & ADU Company
Tom Barrett founded this company in 1998, and he’s been answering his own phone ever since. When someone calls about a West Hills addition, the person who picks up is someone whose name is on the truck, not a call center reading a script two time zones away. Tom’s sons run the crews. That changes how the work gets done: the person quoting your ADU is the person who will be there when the inspector signs off.
West Hills homeowners have a particular reason to care about that. This is a community shaped by two disasters, the 1994 Northridge Earthquake and the 2018 Woolsey Fire, and the homes here carry those histories in their framing and their permits. A contractor who’s never worked in the Very High Fire Hazard Severity Zone will walk into a routine addition and miss the Chapter 7A requirements until the inspector flags them. We don’t. Our Home Additions & ADU team has been through enough LA County plan checks in this corridor to know what the reviewer is going to ask before you’ve paid for the first set of drawings.
And when the work is done, you get the 90-Day Done Right Promise in writing. Something isn’t right? One call, and Tom comes back. He lives close enough that he’d rather hear about it from you than see it from his truck.
Our Home Additions & ADU Services in West Hills
ADU Design & Permitting
In West Hills, an ADU is rarely a simple “drop a shed in the yard” project. Hillside lots in 91307 often need grading review, and nearly everything east of the Simi Hills edge falls under the VHFHSZ rules that fire officials take seriously. That means ignition-resistant siding, ember-proof vents, and Class A roof assemblies on any new structure. We handle the design and the permit package as one thing, not two, so the drawings you submit already answer the questions the county will ask. Permits pulled on every eligible job; inspections signed before you write the final check.
Garage Conversion ADU
West Hills has hundreds of late-1950s through early-1980s ranch homes with attached garages that have long since stopped holding cars. A garage conversion in the 91307 and 91308 zip codes typically runs $30,000 to $80,000, depending on whether you need seismic anchors, a new foundation pour, or upgraded electrical service. On older West Hills garages, we frequently find slab cracks from the Northridge quake that were never addressed, and that’s exactly the kind of thing you want found before drywall goes up, not after.
New Detached ADU
A new detached ADU on a West Hills lot is a different animal than one in Canoga Park or Reseda. The Santa Ana winds that funnel through the mountain passes mean ember-resistant construction is not optional; it’s mandatory. We build detached units from $90,000 to $220,000, including the site prep, utility trenching, and the fire-rated assemblies the county will inspect. If your lot backs up to open space near the Simi Hills, the requirements get stricter still, and we plan for that from day one rather than treating it as a surprise.
Junior ADU & Interior Conversion
Sometimes the right answer in West Hills is not adding square footage at all; it’s reworking what’s already there. A Junior ADU inside the existing footprint, often a converted den or oversized laundry room, can create a private living space for a family member without triggering the full Chapter 7A review that a conditioned-square-footage increase would bring. We see West Hills homeowners choose this route when a parent needs to move in but the budget doesn’t stretch to a full detached unit. These projects often pair well with our Kitchen Remodeling in West Hills work, especially when the JADU shares a wall with the main kitchen.
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.
Trusted Brands We Service in West Hills
We install materials you can look up before you sign anything. For windows and doors on West Hills additions, we carry Simonton, Ply Gem, and PGT lines, including impact-rated and multi-pane options that meet the fire-zone glazing requirements. Because we’re serving West Hills homes directly, we’re not waiting on parts from a supplier three states away when a residential window order for a sunroom or second-story addition needs to match the existing openings. We know what the county will accept on a 91308 hillside lot, and we specify accordingly.
Common Home Additions & ADU Problems We See in West Hills Homes
- Chapter 7A fire-rated assemblies missed on the first plan check. Contractors who work mostly in flatland Valley cities draft additions that would fly in Canoga Park, then stall out in West Hills plan review. Class A roofing, ember-resistant vents, and one-hour wall assemblies are standard here, not upgrades.
- Slab and foundation movement from the 1994 Northridge Earthquake. Many West Hills ranch homes carry hairline cracks and settled corners that were patched but never properly addressed. A room addition tied to a compromised slab becomes a problem you’re paying to hide.
- Santa Ana wind exposure tearing at poorly flashed roof-to-wall connections. West Hills sits at the valley’s western edge where the wind accelerates through the passes. Additions that aren’t detailed for 60 mph gusts fail at the intersections before they fail anywhere else.
- Coastal contractors underestimating summer heat during pours. The valley-bowl heat in West Hills accelerates concrete curing in July and August. Scheduling pours without accounting for that means cracked slabs and a foundation inspection you don’t want to fail.
Pricing for Home Additions & ADU in West Hills, CA
You asked, so here are the numbers we give West Hills homeowners before anyone signs a contract. A room addition on a standard 91307 ranch lot runs $45,000 to $130,000. A detached ADU runs $90,000 to $220,000. A garage conversion runs $30,000 to $80,000. A Junior ADU or interior conversion often falls between the garage number and the low end of the room addition range. What moves the number is hillside grading, fire-rated assemblies, seismic retrofit scope, and utility trenching distance. Every allowance and every scope change comes to you as a written change order before work proceeds. No surprise invoice at the end, because the allowance that isn’t on paper is a surprise waiting for a date. Call (877) 610-1318 and we’ll give you a line-item estimate for your specific lot.
We Also Serve Cities Near West Hills
Our crews work throughout the western San Fernando Valley, so if you’re just over the line in West Hills or nearby, give us a call. We regularly serve Canoga Park, Woodland Hills, Calabasas, and Chatsworth. If you’re planning a larger project, ask about pairing your addition with Bathroom Remodeling in West Hills while the walls are still open.
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 - Home Additions & ADU in West Hills
We can typically be at a West Hills property within one to two business days for an initial walk-through, and we don’t charge a trip fee inside the county. Call (877) 610-1318 and a live person picks up; no voicemail maze and no out-of-state call center. If you have a written estimate from another contractor, bring it and we’ll give you a free second opinion.
Yes. We work throughout 91307 and 91308, including the hillside streets along Valley Circle Boulevard, the neighborhoods east of Platt Avenue, and the tracts near Bell Canyon. Hillside lots take longer to quote because we’re walking the grade and the fire-zone requirements, but we don’t turn them down. The permit inspector works for you, not for me; that’s why I like him there.
We are not typically the first call for fire suppression or structural emergency shoring, and we would never claim to be. But we do handle the rebuild and the reconstruction that follows, including full fire-damage rebuilds in the West Hills VHFHSZ and seismic repairs after an earthquake. There is no same-day addition, and any contractor who tells you there is should be asked for that in writing. Permits and inspections govern this kind of work, and we follow them.
Yes, and it’s not close. The same ADU drawings that cost $90,000 to build in West Hills can cost 10% to 20% less in a flatland community outside the fire hazard zone. The difference is not labor or greed; it’s the Class A roof assembly, the ember-resistant vents, the one-hour wall assemblies, and the plan check time the county requires. If you live in 91307 near the Simi Hills edge, expect to carry the fire-rated materials cost on any conditioned-space addition. That’s a West Hills fact, not a Barrett & Sons markup.
Every project comes with the 90-Day Done Right Promise, written on the contract, not buried in fine print. If something isn’t done right, Tom Barrett comes back and makes it right. One call. Beyond that, we stand behind the manufacturer warranties on materials like Simonton and Ply Gem windows, and the workmanship carries our name, not a subcontractor’s. Ask anyone on your street, or look up the license number yourself.
Ready to talk about your West Hills addition or ADU? Call (877) 610-1318 for a free estimate. Scope in writing, allowances in writing, change orders in writing. That’s how we’ve done it since 1998.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving West Hills and the western San Fernando Valley since 1998.