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
Adding a room to your Hidden Hills home is a bigger decision than most contractors will admit. It is not just square footage. It is a new roofline, a deeper foundation pour, electrical load recalculations, and a stack of paperwork that starts with the Hidden Hills Community Association and runs through Los Angeles County. The good news: a well-planned room addition in Hidden Hills typically runs $280 to $410 per square foot for build-out, and the project can be scoped, priced in writing, and scheduled without guesswork. We are Sutton ADU Builders, and our Room Addition Contractor team has run additions on parcels from Long Valley Road to Jed Smith Road. If you are weighing the project, call (472) 248-8213 and we will walk you through it plainly.
Why Sutton ADU Builders Is Hidden Hills’s Preferred Room Addition Contractor Company
Finding trusted ADU Builders in Hidden Hills matters because this is not a market where you can send a nameless crew and hope for the best. The lots are large, the homes are custom, and the review process is exacting. That is why we send every homeowner the name and photo of each technician before they ever knock on a door. It is called the Threshold Standard, and it means every field worker is background-checked, identity-verified, uniformed, and carrying photo ID. You know who is on your property. No exceptions.
Founded in 2006, Sutton ADU Builders is part of the Threshold Group family. Our reputation in Hidden Hills rests on a simple operating rule: a written price is delivered before any work begins, and the 365-Day Done Right Promise covers defects in workmanship for one full calendar year from project completion. If something we built does not hold up, we fix it. No haggling, no fee, and a free second visit is part of the promise.
Local knowledge is the other piece. We know that Hidden Hills enforces its own design review before the county gets involved, and we plan permits around that sequence. We know which oak canopies need arborist sign-off. We know that a half-acre parcel off Round Meadow Road may have radically different setback realities than one backing up to the 101 corridor near the Calabasas edge. That knowledge keeps a project from stalling.
Our customers in Hidden Hills expect a builder who answers the phone when they call. You will get a live person, 24 hours a day, 7 days a week. When you call (472) 248-8213, you reach someone who can actually help you.
In Law Suite Builders in Hidden Hills
In Law Suite Builders in Hidden Hills are often the right call for families who want an attached guest space that is not legally a separate dwelling but still functions like one. An in-law suite can include a bedroom, a bathroom, and a small kitchenette, all built as part of the primary home’s footprint. In Hidden Hills, this route usually avoids the longer ADU approvals while still giving an aging parent or returning adult child privacy and independence. Expect to pay $180,000 to $270,000 for a 450-to-600-square-foot attached suite, depending on finishes and how much plumbing you are running.
Equestrian-Zone Setbacks and Suite Placement
Most Hidden Hills parcels carry equestrian zoning, which means your suite addition has to respect stable and corral setbacks as well as standard property-line rules. We design around those from the first site visit. A suite placed too close to a horse-trailer turnaround or a barn access lane will get bounced by the Community Association review, and that review happens before the county will even look at your permit.
What a Hidden Hills In-Law Suite Needs to Succeed
You need a private entrance or a clear interior path, a bathroom with a full shower, and enough closet space to meet county habitability standards. We pull all plumbing and electrical subpermits as part of the build. On a recent job off Jed Smith Road, we tied a new suite into the existing water heater line and added a dedicated 20-amp circuit for a small kitchenette, all documented in the written price before we broke ground.
ADU Conversion in Hidden Hills
ADU Conversion in Hidden Hills usually means turning an existing structure, often a garage or a stable wing, into a rentable or multi-generational dwelling unit. This is different from new construction because the bones are already there, but the conversion still has to meet current energy code, fire separation, and ceiling-height requirements. A garage-to-ADU conversion in Hidden Hills commonly runs $150,000 to $240,000. That range assumes the existing slab and framing are sound. If you are converting a structure with old horse-stall framing or one that predates modern footings, add $25,000 to $45,000 for reinforcement.
Oak Tree Permits and Existing Structures
When a conversion bumps up against a protected oak canopy, Hidden Hills requires an Oak Tree Permit for any root-zone or canopy disturbance. That rule applies even when you are not adding a new footprint. We bring the arborist in early, document the root zone, and fold the permit into the timeline so it does not blindside you after demolition starts.
When Conversion Costs More Than New Build
Honest truth: some Hidden Hills owners are surprised when a conversion bids out higher per square foot than building fresh. Old structures have surprises: termite sill damage, non-code ceiling heights, inadequate electrical service. A 1970s three-car garage off Long Valley Road needed a new subpanel, roof re-sheathing, and foundation doweling before we could frame the interior walls. The written price we delivered accounted for all of it, and the final invoice matched.
Trusted Brands We Service in Hidden Hills
Our Hidden Hills team carries materials and parts for the brands our customers already know. We install and finish James Hardie siding and exterior systems on room additions and ADUs, and we have direct experience with prefabricated units from Abodu, Cover, and Dvele when a factory-built module makes more sense than stick framing. That matters because a Hardie-clad addition has to be painted, flashed, and ventilated correctly the first time. We stock matching Hardie trim profiles for local homes and can usually source what we need within a week, not a month.
Common Room Addition Contractor Problems We See in Hidden Hills Homes
- Skipped Community Association review. Hidden Hills requires architectural committee approval before the county will issue a building permit, and skipping that step stalls the project for weeks if not months. We file the association application first, every time, and walk plans through that gate in person.
- Missed Oak Tree Permit triggers. On half-acre and larger parcels, canopy and root-zone disturbance requires a separate Oak Tree Permit. We flag this in the first site walk and coordinate with the city arborist before drawings are even finalized.
- Old slab and footing surprises. Many Hidden Hills ranch homes built before modern seismic codes have slabs that were never engineered for a load-bearing addition. We core-test the slab and review the original plans before we commit to a price.
- Panel and service overload. A 480-square-foot addition with a new bath and kitchenette will often require a subpanel upgrade. One older home off Round Meadow Road had a 100-amp main that could not legally serve the new loads. We spec’d a new 200-amp service and included that line item in the written price before any work started, rather than dropping it as a change order.
Pricing for Room Addition Contractor in Hidden Hills, CA
Room additions in Hidden Hills run a real range depending on what you are adding. A basic 400-square-foot bedroom suite with a full bath typically falls between $210,000 and $280,000. A larger 500-to-600-square-foot family room or guest wing that ties into a new roofline and requires foundation work usually runs $290,000 to $380,000. Site work is the biggest variable: grading, drainage, oak-root protection, and access on equestrian-zoned parcels can add $15,000 to $45,000. We give you a written price before any work begins, line by line, so you are not guessing. Call (472) 248-8213 and we will come out, measure, and price it properly. The estimate is free.
We Also Serve Cities Near Hidden Hills
Our crews serve the surrounding region, including Los Angeles, Long Beach, Anaheim, and Riverside. If you are considering a room addition or ADU project anywhere in the area, our Room Addition Contractor team can bring the same written pricing and Threshold Verified crew standards to your property.
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
You need Hidden Hills Community Association architectural review, a Los Angeles County building permit, and in most cases an Oak Tree Permit if the work affects a protected canopy or root zone. The association review comes first, and the county permit will not be issued until that approval is on file. Call (472) 248-8213 if you want us to review your specific parcel and tell you exactly which permits apply.
Plan on 8 to 14 months from first design meeting to final inspection in Hidden Hills. The wildcard is the association review, which adds 4 to 10 weeks depending on committee scheduling, and the oak-canopy review if the arborist requires protective fencing. Construction itself usually runs 16 to 22 weeks for a 400-to-600-square-foot addition.
Yes. An attached in-law suite with a bathroom and small kitchenette is often the quickest path to multi-generational living because it is treated as part of the primary home rather than a separate ADU. The suite still needs association review and county permitting, but the approval sequence is generally shorter than a detached ADU. We can price both options during the same site visit.
Undocumented slab conditions, hidden termite damage, roofline complications, and oak-root conflicts discovered during excavation are the four things that can move a price. We mitigate each by doing a slab core test, a pest inspection, and an arborist review before we finalize your written price. When we hand you a number, it is meant to be the number.
Yes. A garage-to-ADU or stable-wing conversion requires its own Los Angeles County building permit, and it must meet current energy and fire codes even if the structure is old. If the conversion touches a protected oak’s root zone, the Oak Tree Permit applies as well. We handle all three paper trails and coordinate inspections. For a precise quote on your conversion, call (472) 248-8213.
Call Sutton ADU Builders at (472) 248-8213 to schedule your free estimate. We will send a named, photo-badged technician to your Hidden Hills property, walk the lot with you, and deliver a written price before any work begins.
Written by Miles Hartwell, Owner at Sutton ADU Builders, serving Hidden Hills and the surrounding region since 2006.
