A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateFast, Reliable Home Addition Contractor Across Calabasas
A home addition in Calabasas typically costs between $180 and $420 per square foot depending on scope, site conditions, and whether you’re building a second story, garage conversion, or ground-level bump-out. Most Calabasas additions take 4 to 9 months from first plan to final inspection, with hillside parcels and fire-zone requirements adding both time and cost. Benson ADU Builders writes a fixed price before any work starts, so you know the number before the first permit gets pulled. Call (903) 568-7222 to schedule a free estimate in Calabasas.
We know this city’s approval process cold. That matters more here than in flatland LA neighborhoods. Calabasas sits almost entirely within the Santa Monica Mountains’ High Fire Hazard Severity Zone, and much of the hillside residential stock is governed by the Calabasas Municipal Code’s hillside/slope-density and oak-tree preservation provisions. A second-story or garage-conversion addition here routinely triggers extra brush-clearance, fire-resistant construction, and grading review that cities like Canoga Park or West Hills don’t require. If your contractor doesn’t plan for that on day one, your permit gets stuck and your calendar resets by months.
Written by Troy Eastman, Owner at Benson ADU Builders.
Why Benson ADU Builders Is Calabasas’s Preferred Home Addition Contractor Company
Calabasas homeowners call us because we put the plan and the price in writing before anything gets built. No verbal estimates that quietly grow. No scope creep discovered at the framing walkthrough. Our written price covers the full scope, and our 365-Day Done Right Promise means if something isn’t right within a full year of completion, we make it right. Every project also carries a written guarantee and a free second visit if any covered repair fails.
We’re part of the Relay Home Co. family, established 2006. Each location is independently owned and operated under The Relay Visibility Guarantee, and our Calabasas crews are background-checked and arrive in uniform. You’ll always know who’s walking onto your property. There’s also a live person answering the phone around the clock, every day of the year. No voicemail loops, no waiting until Monday.
We’ve built additions across Calabasas, from the flat lots along Las Virgenes Road to steep hillside parcels in the Calabasas Highlands and the gated neighborhoods around Lake Calabasas. That range matters. A contractor who only builds on flat ground will misjudge your retaining, grading, and fire-hardening costs. A contractor who only builds hillside work will over-engineer your flat-lot second story. We scope each Calabasas addition against the actual conditions on your parcel, then hand you a line-item written price before you commit.
Second Story Addition Contractor in Calabasas
A Second Story Addition Contractor in Calabasas has to account for something most cities never deal with: pre-1980s hillside homes that were never engineered for a stacked second floor. Many Calabasas houses built in the 1960s and 1970s have roof framing, shear walls, and foundations sized only for the original single-story load. Before we draw a single elevation, we check the existing structure against the added weight. If the framing is undersized, the plan has to re-engineer the bearing path, which changes both cost and schedule.
Engineering and Setback Reality
Hillside slope-density provisions in Calabasas often force the rear elevation of a second story to step back further than a standard LA County setback. That means less buildable area than the lot size suggests. We built a second-story addition over an existing two-car garage off Mulholland Drive in the Calabasas Highlands where the existing roof framing turned out to be undersized for the new load and the slope setback forced us to re-engineer the rear elevation. Because the parcel sits in the brush-clearance overlay, we also upgraded the new walls and eave details to fire-resistant assemblies per the city’s WUI standards before the framing inspection. The result was a permitted second-story primary suite that passed final without a single correction notice.
What It Costs
A second-story addition in Calabasas runs roughly $250 to $420 per square foot. The higher end reflects hillside parcels with retaining needs, fire-resistant exterior assemblies, and structural upgrades to the existing lower floor. A flat-lot addition in the neighborhoods near A.C. Stelle Middle School will sit at the lower end. Expect engineering and plan-check fees to add another $8,000 to $18,000 on top of construction, especially when oak-tree or slope-density review is triggered.
Garage Addition Contractors in Calabasas
Garage Addition Contractors in Calabasas handle two very different jobs: converting an existing garage into living space, or building a new garage with living area above it. Both trigger city-specific review steps that flatland contractors routinely miss. A garage conversion in Calabasas almost always requires a check against the oak-tree preservation ordinance if any protected tree is within the root zone, plus fire-hardening review if the parcel is in the brush-clearance overlay. A new garage addition with living space above adds hillside grading review on sloped lots.
Converting vs. Building New
Converting an existing attached garage in Calabasas runs $120 to $220 per square foot, assuming the slab and walls are sound. Many hillside garages from the 1970s and 1980s are not sound. They were built as car storage, not living quarters, and the slab may not meet current insulation or moisture requirements. We test before we quote. A new garage addition with an ADU or suite above runs $220 to $380 per square foot, with the upper end driven by retaining walls, footings on sloped grade, and WUI-compliant exterior materials.
Combining a Garage ADU with Living Space Above
Calabasas has real momentum around ADU work, and a garage-plus-ADU stack is one of the most efficient ways to add rental income and living space on one footprint. We can build the lower garage to code and frame the upper unit from the same foundation, which saves on grading and site work compared to two separate structures. If you want a prefab or modular approach, we build with Abodu, Cover, Dvele, and Mighty Buildings panels, so you get a tightly controlled factory-built envelope with local Calabasas fire-hardening applied at assembly.
Trusted Brands We Service in Calabasas
Benson ADU Builders is authorized to build with Abodu, Cover, Dvele, and Mighty Buildings, and we source James Hardie cladding for additions that need superior fire resistance. For Calabasas customers, that means you can research these brands independently before you ever sign with us. Prefab panels arrive with factory tolerances, which cuts framing time and reduces exposure to weather delays. We carry the local hardware, flashing, and WUI-compliant vent and eave components required for Calabasas fire-zone assemblies, so we’re not waiting on a parts order when your inspection is scheduled.
Common Home Addition Contractor Problems We See in Calabasas Homes
- Undersized existing framing on hillside homes. Many Calabasas houses built before 1980 were framed for single-story loads only. A second-story addition requires a structural review before plans are drawn, and retrofits often add $15,000 to $40,000.
- Oak-tree preservation review resetting the schedule. If a protected oak sits near the addition footprint, the plan set goes through tree-review before building approval. Missing that step means a plan kickback and months of delay.
- Brush-clearance and WUI exterior requirements. Calabasas hillside parcels in the fire hazard zone require fire-resistant wall assemblies, eave details, and venting that standard LA County additions don’t. A contractor who prices off a flatland per-square-foot number will be off by tens of thousands.
- Slope-density limits shrinking the buildable envelope. The hillside/slope-density provisions in the Calabasas Municipal Code can cap how far a rear elevation extends. What looks like a big buildable lot may yield a much smaller addition once setbacks apply.
Pricing for Home Addition Contractor in Calabasas, CA
Here’s an honest look at what Calabasas additions cost in 2026.
- Ground-level room or bump-out addition: $180 to $280 per square foot
- Garage conversion to living space: $120 to $220 per square foot
- New garage with ADU above: $220 to $380 per square foot
- Second-story addition: $250 to $420 per square foot
- Plan-check, engineering, and permit fees: $8,000 to $18,000 typical, more on hillside parcels
The biggest cost drivers in Calabasas are slope, fire-zone exterior requirements, oak-tree review, and the condition of the existing structure. A flat-lot addition off Las Virgenes Road will price lower than the same square footage on a brush-covered hillside off Mulholland Drive. We give every Calabasas customer a written line-item price before work starts. No change orders on scope we’ve already agreed to. Call (903) 568-7222 to schedule your free estimate.
We Also Serve Cities Near Calabasas
Our crews regularly work in Woodland Hills, West Hills, Topanga, and Canoga Park, and we understand how the fire-zone and hillside rules shift as you cross the Calabasas city line. If you’re researching a Home Addition Contractor for a property near the Calabasas border, our written-price process works the same way no matter which side of the line you’re on. See our Home Addition Contractor in Calabasas coverage for details.
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 About Home Addition Contractor in Calabasas
Yes. Most Calabasas parcels sit in the Santa Monica Mountains High Fire Hazard Severity Zone, so a second-story addition triggers WUI-compliant exterior assemblies: fire-resistant wall cladding, ember-resistant vents, and protected eave details. Standard LA County flatland additions don’t carry the same requirements. This adds roughly 8 to 15 percent to exterior costs. Call (903) 568-7222 and we’ll tell you exactly what applies to your parcel.
Plan-check and inspection in Calabasas typically adds 2 to 4 months beyond a flatland LA County timeline, and longer if oak-tree review or slope-density provisions are triggered. The full addition, including construction, usually runs 4 to 9 months for a garage conversion and 6 to 10 months for a second story on a hillside lot. We sequence the permit pathway before construction starts so you’re not waiting on a plan kickback mid-project. Call (903) 568-7222 for a realistic timeline on your property.
Yes, and we do this regularly in Calabasas. A garage ADU conversion with a new living space above combines both uses on one foundation, which saves grading and site work compared to two separate structures. The existing garage slab and walls must be evaluated first; many 1970s and 1980s Calabasas hillside garages need structural upgrades. Call (903) 568-7222 for a free assessment and a written price.
Three things, and we tell you about all of them before we begin: hidden structural deficiencies in the existing home sheathing or foundation, unexpected site conditions like subsurface rock on slope lots, and owner-selected finish upgrades after the contract is signed. The first two are uncovered during inspection and remediation planning, not mid-build, because we do the structural review before plans are finalized. The third is entirely in your hands. Our 365-Day Done Right Promise covers workmanship, not the cost of changed selections. Call (903) 568-7222 to get your written line-item price.
Yes. We build with Abodu, Cover, Dvele, and Mighty Buildings, and we apply local Calabasas fire-hardening at assembly so the factory-built panel arrives ready for WUI inspection. Prefab panels cut framing time and reduce weather exposure on hillside sites, which keeps your calendar tighter. You can research each brand independently, then call (903) 568-7222 and we’ll scope the best option for your addition.
Written by Troy Eastman, Owner at Benson ADU Builders, serving Calabasas.
