A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateFast, Reliable Room Addition Contractor Across Hidden Hills
A room addition in Hidden Hills typically costs $180 – $420 per square foot depending on finishes, foundation work, and whether your parcel triggers design-review overlays. Most projects we bid in Hidden Hills land between $140,000 and $420,000 for a full permitted addition, with smaller bump-outs starting around $90,000. Benson ADU Builders handles the whole process, from Hidden Hills design-review submittal through LA County inspection and final paint. Call (903) 568-7222 and we’ll walk your lot before you commit to anything.
Hidden Hills isn’t like building in Calabasas or Agoura Hills. Nearly every lot sits at an acre or more, most homes are custom estates, and the gated equestrian planning means your addition has to work within Hidden Hills Municipal Code overlays that don’t apply two miles down the road. We know that because we’ve pulled those approvals. Troy Eastman leads our team, and he’s the one who walks Hidden Hills parcels with you on the first visit, before any design work starts.
Why Benson ADU Builders Is Hidden Hills’s Preferred Room Addition Contractor Company
Homeowners in Hidden Hills keep calling us back because we put the design-review risk on the table in the first meeting, not the third. Our Room Addition Contractor team has handled additions on parcels off Long Valley Road, Round Meadow Road, and Jed Smith Road, and we know which overlays apply before you spend a dollar on plans. That upfront honesty matters when a Hidden Hills design-review cycle can stretch months longer than a standard LA County permit.
Every Hidden Hills project gets a written price before work starts, a 365-Day Done Right Promise, and a written guarantee on the finished addition. Our crews are background-checked and arrive in uniform. You’ll know the names of the people on your property. That’s the Relay Visibility Guarantee, and it’s stamped on every Hidden Hills contract we sign.
We’re part of the Relay Home Co. family, founded 2006, and our Hidden Hills work is coordinated through the brand’s Los Angeles office. Scheduling and dispatch run through that office; the crews you’ll see on-site serve Hidden Hills directly.
In Law Suite Builders in Hidden Hills
In Law Suite Builders in Hidden Hills do a specific job well: they turn underused square footage or a new attached wing into a self-contained living space with its own entrance, kitchenette or full kitchen, bath, and laundry hookup. On Hidden Hills estate lots, we’re often converting a detached garage wing or adding a connected suite off the main house so an aging parent or adult child has privacy without leaving the property. Construction costs for an in-law suite addition in Hidden Hills commonly run $160,000 – $320,000, with a JADU conversion inside existing walls coming in lower, around $70,000 – $140,000. A JADU is a Junior Accessory Dwelling Unit, by the way: a smaller, attached unit with its own entrance, capped at 500 square feet under California law.
Attached suite additions on large Hidden Hills parcels
On a one-acre Hidden Hills lot, you have room to build out rather than up. We design attached in-law suites that connect through a shared wall or a short hallway, so the addition reads as part of the original home from the street. The Hidden Hills design-review board cares about that roofline continuity more than any jurisdiction around here, and we account for it before drawings go in.
Garage and bonus-room conversions that become legal living space
Many Hidden Hills homes have oversized garages or bonus rooms that were never permitted as habitable space. Converting one into an in-law suite means adding insulation, a proper foundation check, egress windows, and often a shear-wall upgrade. We price that work honestly before the permit application, which matters because Hidden Hills will inspect what’s already there before they approve what you’re adding.
ADU Conversion in Hidden Hills
ADU Conversion in Hidden Hills usually means taking a structure that already exists, like a detached garage, pool house, or barn-style outbuilding, and turning it into a legal Accessory Dwelling Unit. California ADU law streamlines the permit path, but Hidden Hills adds its own design-review layer on top, and that’s where most conversion projects stall. Build costs for a garage-to-ADU conversion in Hidden Hills typically run $120,000 – $240,000. A new detached prefab ADU from brands like Abodu or Cover often lands between $180,000 and $350,000 once site work, foundation, and Hidden Hills design-review compliance are included.
Garage conversions under Hidden Hills overlays
Your garage is already set back and has a foundation, so the conversion itself is efficient. The Hidden Hills piece is matching the exterior finish to the main residence, which the design-review board will check. If your home is ranch-style with James Hardie siding, the converted garage needs to read that way too, not look like a prefab box dropped on the side of the property.
Prefab panel systems sized for estate lots
We build with Abodu, Cover, and Dvele panels when the site allows delivery access. On Hidden Hills parcels, the access roads and equestrian trails around Round Meadow Road and Long Valley Road can constrain a crane or flatbed, so we verify the site route before recommending a panel system. When prefab isn’t practical, we go site-built, which gives you more flexibility with Hidden Hills’s design-review feedback.
Trusted Brands We Service in Hidden Hills
When Hidden Hills homeowners ask what materials hold up here, we point them to names they can research themselves: James Hardie siding and trim, plus prefab ADU and addition systems from Abodu, Cover, and Dvele. We keep a working relationship with all of them, and we can quote a James Hardie-clad addition or an Abodu ADU conversion without a months-long wait for pricing. That matters on Hidden Hills projects because the design-review board wants to see specific materials and roofline details before they’ll sign off, and those brands give us clean specs to submit.
Common Room Addition Contractor Problems We See in Hidden Hills Homes
- Hidden Hills design-review timelines get underestimated. Owners are told 6 to 8 weeks, but board meeting cycles and requested revisions can stretch that to 12 weeks or more. We work that timeline into the schedule from day one, instead of acting surprised later.
- Older estate framing fails the engineer’s load check. On 1960s and 1970s Hidden Hills homes, the original framing often isn’t rated for the new roof and floor loads a room addition brings. That means a structural retrofit, a new beam line, or foundation thickening before framing starts.
- Spec ADU kits don’t match Hidden Hills design guidelines. A stock panel design with the wrong roof pitch, siding, or color gets kicked back by the design-review board. We work through Hidden Hills Municipal Code requirements before you buy a kit, not after.
- Parcel overlays catch owners off guard. Many Hidden Hills lots carry Hillside or Oak Tree/Scenic Corridor overlays, which can restrict where you build and what you can remove. We check the specific parcel before the first design meeting.
Pricing for Room Addition Contractor in Hidden Hills, CA
Hidden Hills additions run higher than the LA County average because the land, the homes, and the approvals are all more involved. Here’s what we’re seeing in 2025 and 2026:
- Bump-out addition (200 – 400 sq ft): $90,000 – $170,000
- Full primary-suite addition (400 – 600 sq ft): $150,000 – $280,000
- In-law suite addition with kitchenette and bath: $160,000 – $320,000
- Garage-to-ADU conversion: $120,000 – $240,000
- Detached prefab ADU (Abodu, Cover, Dvele): $180,000 – $350,000
- Structural retrofit added mid-project (when older framing fails): $18,000 – $60,000
What drives cost in Hidden Hills: design-review revisions, structural upgrades on older estate homes, utility runs across a one-acre lot, and finish materials matched to a custom main house. We give every Hidden Hills homeowner a written line-item price before work starts. If the engineer finds something behind the walls later, we show you the photos and the revised line item before we touch it. Call (903) 568-7222 for a free estimate.
We Also Serve Cities Near Hidden Hills
Benson ADU Builders works throughout the region around Room Addition Contractor in Hidden Hills, including Los Angeles, Long Beach, Anaheim, and Riverside. If your property sits within reach of our crew routes, we’ll come out, walk the lot, and give you the same written pricing we give Hidden Hills homeowners.
Serving Hidden Hills, CA - Our Local Coverage Area
We’re based in the Hidden 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 Room Addition Contractor in Hidden Hills
Most Hidden Hills room additions need both: an LA County building permit plus a Hidden Hills design-review approval. Because nearly every lot is at least one acre and most homes are custom estates, even a modest bump-out often triggers design-review submission, and many parcels carry Hillside or Oak Tree/Scenic Corridor overlays that add a review layer you wouldn’t face in Calabasas. We handle both tracks from the start. Call (903) 568-7222 to find out what your specific parcel will require.
Plan on 6 to 10 months from first design meeting to final inspection, and accept that the Hidden Hills design-review piece can add 8 to 14 weeks on its own. Construction itself, once permits clear, usually runs 3 to 5 months for an addition in the 400 to 600 square foot range. We give you a written schedule with milestones, and the Relay Visibility Guarantee includes real-time tracking so you see where things stand without chasing us. Call (903) 568-7222 to get a project calendar started.
The most common problem is original framing that doesn’t meet current load requirements once a new addition ties in. On 1960s and 1970s Hidden Hills builds, we frequently find roof and floor framing that needs a beam line, shear-wall upgrade, or foundation thickening. That’s a code-driven retrofit, not an upsell. We show you the engineer’s report and the revised line item before any of that work proceeds. For an exact scope on your home, call (903) 568-7222; the estimate is free.
Yes, with the right site access. We build with Abodu, Cover, and Dvele panel systems, and on many Hidden Hills parcels the delivery route works for a flatbed or crane. The catch is Hidden Hills design review: the panel system’s exterior, roof pitch, and trim have to match the design guidelines, so we spec those details before you order anything. Call (903) 568-7222 and we’ll check your parcel’s access and overlay status in the first visit.
Three things, mostly: an engineer finds structural work the original drawings couldn’t have caught, the Hidden Hills design-review board requests material or design revisions after submittal, or you change the finish selections mid-project. Our written price covers what we can see and verify before we open walls. When something hidden changes the scope, you get the revised line item in writing before we proceed, never after. Call (903) 568-7222 to talk through your project and get a written price.
Written by Troy Eastman, Owner at Benson ADU Builders, serving Hidden Hills and the surrounding LA County area.
