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 Malibu
A detached ADU in Malibu typically costs $90,000-$220,000, a garage conversion runs $30,000-$80,000, and a full room addition lands between $45,000-$130,000. Timelines stretch longer here than almost anywhere in LA County because of the Coastal Commission layer, not because the work itself is harder. That’s the honest answer. If you’re weighing bids for an Home Additions & ADU project on a PCH lot or up in the Santa Monica Mountains, call us at (877) 610-1318 and we’ll walk you through what a compliant quote actually includes.
We’re Barrett & Sons Construction, and Tom Barrett’s sons run the crews. We work in the 90263, 90264, and 90265 zip codes every month. When a Malibu homeowner calls, a live person answers. When you ask why a Coastal Development Permit adds four to nine months before we even pour, you get a straight answer from someone who’s filed that paperwork for beachfront lots, hillside rebuilds, and everything between.
Why Barrett & Sons Construction Is Malibu’s Preferred Home Additions & ADU Company
Homeowners in Point Dume, Sunset Mesa, and central Malibu keep our number because we don’t quote one thing on the phone and show up with another. Every scope, every allowance, every price change comes as a written change order before work moves. That matters a lot when a Coastal Commission condition forces a foundation redesign midway through permits.
Tom publishes his name, his address, and his license number. Look it up before you sign anything. The permit inspector works for you, not for me. We’ve had Malibu customers tell us their previous contractor said the Coastal Development Permit was optional. It isn’t. We pull permits and get inspections signed on every eligible job, and we don’t frame a single wall until the paperwork says we can.
Crews are background-checked and uniformed. We carry premium brands across every trade: Andersen and Marvin on windows, GAF and CertainTeed on roofs, Belgard and Techo-Bloc on hardscapes. Materials you can look up, not mystery brands off a van. And every job we finish in Malibu is backed by our written 90-Day Done Right Promise: if it’s not right, Tom comes back and makes it right, one call.
Our Home Additions & ADU Services in Malibu
ADU Design & Permitting
This is where Malibu projects win or die. A compliant ADU plan in the coastal zone requires a California Coastal Commission Coastal Development Permit stacked on top of city permits, plus Chapter 7A ignition-resistant construction details on the drawings before LA County fire will sign off. We handle the full permit package: Coastal Commission application, city submittal, fire review, and the revision cycles. Expect this to add months to your timeline. Expect any contractor who skips it to hand your project a stop-work order.
Garage Conversion ADU
Converting an existing garage in Malibu is often the fastest path to a rental unit or in-law suite, but the existing structure has to be brought up to current code. Many garages in the 90265 corridor were built before ember-resistant vent requirements existed. We upgrade the assemblies, add the Class A roofing where required, and pull the Coastal Commission permit if your garage sits within the coastal zone. Budget $30,000-$80,000 depending on what the existing slab and framing can support.
New Detached ADU
Building new on a Malibu lot means foundations get complicated fast. Beachfront parcels in the 30-40 foot width range often require deep caissons instead of spread footings because the sandy, liquefiable soils won’t hold a conventional slab, and the Coastal Commission limits how much beach area the foundation can occupy. Hillside lots in the Santa Monica Mountains add geotech reports and often fire-road access constraints. A detached ADU here runs $90,000-$220,000 all-in with permits.
Junior ADU & Interior Conversion
A JADU inside the existing home footprint is the one ADU type that sometimes moves faster in Malibu, since it triggers fewer Coastal Commission reviews when the exterior envelope doesn’t change. That said, if you’re converting a garage bay or unfinished bonus room, the fire-hardening requirements still apply to any new assemblies. We’ll tell you upfront whether your specific conversion path avoids the full coastal permit cycle or not.
What happens when you call
- 1
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 Malibu
We stock and install brands that hold up to salt air and fire-weather cycles. For hardscape and paver work on Malibu properties, we regularly use Techo-Bloc and Cambridge Pavers. For concrete and site-prep products, Quikrete and Oldcastle show up on our orders. These aren’t special-order exotics. They’re what we specify because we know how they perform on coastal lots and hillside terrain. If a material won’t survive marine corrosion or a Santa Ana wind event, we won’t put it on your property.
Common Home Additions & ADU Problems We See in Malibu Homes
- Salt-corroded anchor bolts and connectors. Marine air off the Pacific eats standard steel fasteners fast. On a 35-foot-wide PCH beachfront lot in central Malibu, our crew added a detached ADU where the original slab-on-grade showed salt-corroded anchor bolts. We swapped to hot-dipped galvanized hardware, drove caissons through the sandy subfloor, and scheduled every concrete pour around Caltrans moving-lane closures, with the Coastal Commission permit dictating the exact foundation area before we could even rough-in.
- Spread-footing quotes that can’t survive sandy soil. A contractor quotes a conventional foundation on a beachfront lot, hits refusal in loose sand, and suddenly the change order eats your allowance while rough-in stalls for weeks while caissons get engineered. We see this on PCH lots all the time. The fix is engineering the foundation correctly the first time, before the bid is signed.
- Plans missing Chapter 7A fire-hardening details. An ADU plan that omits ember-resistant vents or a Class A roof assembly fails LA County fire inspection sign-off, the permit can’t close, and the insurance claim gets delayed. Nearly all of Malibu sits in a Very High Fire Hazard Severity Zone. The fire code details matter as much as the Coastal Commission details.
- Staging materials on PCH without a Caltrans encroachment permit. That triggers a stop-work order, leaving a half-framed second story exposed to the next Santa Ana wind event. We coordinate moving-lane closures with Caltrans before materials ever hit the site. It’s a permitting layer almost never encountered inland, and skipping it is a costly mistake.
Pricing for Home Additions & ADU in Malibu, CA
| Project Type | Malibu Price Range |
|---|---|
| ADU Construction | $90,000-$220,000 |
| Garage Conversion | $30,000-$80,000 |
| Home Addition | $45,000-$130,000 |
Those are real bid ranges we’ve written for Malibu projects in the 90263, 90264, and 90265 zip codes. What moves the number is foundation type, the coastal permit path, fire-hardening assemblies, and site access. A hillside lot with a difficult fire-road approach costs more to stage than a flat corner lot off Kanan Dume Road. A detached ADU with caissons on a PCH beachfront parcel will run toward the top of that range. A JADU inside the existing envelope can land lower. Call (877) 610-1318 and we’ll give you a written, line-item estimate. It’s free, and it won’t be a phone number that ghosts you when the Coastal Commission asks for revisions.
We Also Serve Cities Near Malibu
Our crews also cover Home Additions & ADU in Malibu and the neighboring communities of Agoura, Agoura Hills, Westlake Village, and Thousand Oaks. The regulatory landscape changes fast once you cross the county line into Ventura, so we keep our permitting knowledge specific to each jurisdiction. If you’re just over the hill in Agoura Hills or Westlake Village, call us. We know the difference between what Malibu requires and what those cities will sign off on.
Serving Malibu, CA - Our Local Coverage Area
We’re based in the Malibu 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 Malibu
Yes, in the coastal zone almost always. Malibu’s coastal-zone rules require a California Coastal Commission Coastal Development Permit on top of city permits for most ADUs, including some interior conversions, because the Commission reviews any change of use or intensification within the coastal boundary. There are narrow exceptions for some JADUs that stay entirely inside the existing structure, but we verify that before you spend money on plans. Call (877) 610-1318 and we’ll check your parcel’s coastal-zone status.
Because the sandy, liquefiable soils under PCH beachfront lots won’t hold a spread footing, and the Coastal Commission limits how much beach area a foundation can occupy. Deep caissons transfer load down to competent soil without expanding the building’s footprint seaward. A spread-footing quote on a beachfront lot is a red flag. Get the foundation engineered before the bid is final, and get the engineering in writing.
In Malibu’s Very High Fire Hazard Severity Zone, Chapter 7A of the California Building Code requires Class A roofing, ember-resistant vents, ignition-resistant exterior assemblies, and tempered or multi-pane glazing on specific exposures. These details go on the approved plans, and LA County fire inspection verifies them before the permit closes. A quote that omits them won’t pass inspection. A quote that includes them is the one you can hand to your insurer later.
Sometimes, but on narrow 30-40 foot lots with little frontage, staging materials and equipment usually requires a Caltrans encroachment permit and a moving-lane closure coordinated weeks in advance. We schedule concrete pours and material drops around Caltrans permits. Builders who skip this get a stop-work order, and that leaves the framing exposed through the next Santa Ana wind cycle. We don’t let that happen.
Documented compliance gives your insurer written proof that the new structure meets current wind-load and Chapter 7A ignition-resistant standards, which can lower rebuild risk and help your rate or coverage eligibility. We keep a permit file with every inspection sign-off and every change order so you can hand the whole package to your agent. The undocumented rebuild is the one that gets penalized after the fact. Call (877) 610-1318 for a free estimate, and we’ll explain exactly what your job will require and what it will cost.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Malibu and surrounding communities since 1998.