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 Los Angeles
A home addition or ADU in Los Angeles typically runs $53,100 to $153,400, and the single biggest factor is whether your property triggers the city’s Mandatory Seismic Retrofit Ordinance before a single wall goes up. We’re Barrett & Sons Construction, and we’ve built additions, garage conversions, and detached ADUs all over Los Angeles, from the flat lots of the San Fernando Valley to hillside parcels in Highland Park where the Hillside Ordinance changes everything about grading and drainage. If you’re planning to add living space, the permit counter will ask about soft-story retrofits, WUI fire-hardening, and slope stability before it asks about square footage. Call Tom Barrett at (877) 610-1318 and we’ll walk the property with you first.
Why Barrett & Sons Construction Is Los Angeles’s Preferred Home Additions & ADU Company
We started in 1998 and we’re still owner-operated. Tom Barrett’s name, address, and license number are published and verifiable, and his sons run the crews that show up to your Los Angeles job. That matters here more than most cities because Los Angeles building departments don’t bend for anyone. We’ve pulled permits and passed inspections on additions and ADUs in Koreatown, Echo Park, and Silver Lake, and we know which plan checkers want to see shear wall calculations before they’ll even open the file.
Los Angeles homeowners keep calling us because of the 90-Day Done Right Promise. It’s written on every contract. If something’s not done right, Tom comes back and makes it right, one call. We also put every scope change, every allowance shift, and every price adjustment on a written change order before work proceeds. No surprise invoices at the end. The allowance that isn’t on paper is a surprise waiting for a date, and we don’t run our business that way.
Our Home Additions & ADU work in Los Angeles is done by background-checked crew members who carry the Barrett & Sons name. A live person answers our phone 24/7, not a voicemail box. When you call about a permit issue in View Park-Windsor Hills or a foundation question in Los Feliz, you get a human who knows your job, not an out-of-state call center.
Our Home Additions & ADU Services in Los Angeles
ADU Design & Permitting
Most Los Angeles ADU projects stall because the design phase ignores the retrofit triggers built into the city’s ordinances. A detached ADU on a hillside lot in Highland Park or Mount Washington isn’t just a floor plan. It’s a grading plan, a drainage study, and often a geotechnical report before the first footing gets poured. We handle design and permitting as one scope, so the ADU you draw is the ADU that passes plan check. Every eligible job includes permits pulled and inspections signed.
Garage Conversion ADU
Converting a garage in Los Angeles means checking whether the structure was built before 1978 and whether it sits under living space. If it’s a 1960s dingbat with tuck-under parking, the city’s Mandatory Seismic Retrofit Ordinance will likely require structural reinforcement before the conversion gets a permit. We evaluate that early, write the retrofit scope into the quote, and keep the project moving instead of getting red-tagged. A garage conversion in Los Angeles typically runs $35,400 to $94,400 depending on retrofit scope.
New Detached ADU
A new detached ADU in Los Angeles runs $106,200 to $259,600, and the spread reflects site conditions more than finish level. Flat lots in the Valley are straightforward. Hillside lots in the Santa Monica Mountains require retaining walls, stepped footings, and drainage that satisfies the Hillside Ordinance. If your property sits in a Very High Fire Hazard Severity Zone, like parts of Bel Air or Tarzana, you’ll also need Class A roofing and ember-resistant venting. We quote all of it up front, in writing.
Junior ADU & Interior Conversion
A junior ADU built within the footprint of your existing Los Angeles house is usually the fastest path to rental income or an in-law suite. These projects still trigger seismic evaluation if the house is pre-1978 wood-frame and you’re adding a second story above it. We handle the structural review as part of the permit package. The permit inspector works for you, not for me. That’s why we like him. He catches what a rushed plan misses.
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 Los Angeles
We don’t install mystery materials off a van. For driveways, patios, and hardscape tied to your Los Angeles addition or ADU, we use Belgard and Techo-Bloc pavers because they hold up under our wet-dry cycles and Santa Ana heat without fading or shifting. For exterior hardscape and retaining walls on hillside lots, we spec Quikrete products for structural concrete and drainage applications. You can look up every brand we install. If you can’t verify it, we won’t put it on your property.
Common Home Additions & ADU Problems We See in Los Angeles Homes
- Un-retrofitted soft-story conditions red-tagging permits. A homeowner adds a second story over a 1960s garage with tuck-under parking, and the city won’t sign off until steel moment frames or plywood shear walls are designed and installed. This adds months and real money. We catch it during the initial walkthrough.
- Hillside drainage failures after framing passes. Rough-in passes, framing passes, then final inspection fails because the ADU’s drainage doesn’t meet Hillside Ordinance requirements. The owner excavates around a finished structure. We design drainage before footings go in.
- WUI fire-hardening omitted from a cheap quote. A property in a Very High Fire Hazard Severity Zone gets an ADU with standard vents and roofing. Stop-work order. Insurance premium rises. The added cost to do it right from the start is a fraction of the retrofit afterward.
- Foundation surprises on 1920s Craftsman homes. Adding a room to a 1920s bungalow in Los Feliz or Highland Park often reveals original foundations that don’t meet current seismic standards. The city requires the existing house to be brought up to code as part of the addition scope. We write that into the plan before demo starts.
Pricing for Home Additions & ADU in Los Angeles, CA
Los Angeles pricing reflects what the building department requires, not just what the contractor charges. A compliant quote includes seismic retrofit design if your property triggers the mandate, WUI-compliant materials if you’re in a fire hazard zone, and Hillside Ordinance drainage and grading if you’re on a slope. A cheap quote leaves those out and hopes the inspector doesn’t notice. He will.
| Project Type | Typical Los Angeles Range |
|---|---|
| Home Addition | $53,100 - $153,400 |
| ADU Construction | $106,200 - $259,600 |
| Garage Conversion | $35,400 - $94,400 |
Every estimate we give in Los Angeles is free. Every change order is written before work proceeds. We don’t quote one price on the phone and hand you a different bill at the door. Call (877) 610-1318 and we’ll put the numbers on paper.
We Also Serve Cities Near Los Angeles
Beyond Los Angeles proper, we work regularly in Koreatown, Echo Park, Silver Lake, and View Park-Windsor Hills. Crews serving those neighborhoods are dispatched from our Los Angeles metro office, so the same crews who know your street also know your permit office. For a broader look at coverage, see Home Additions & ADU in Los Angeles.
Serving Los Angeles, CA - Our Local Coverage Area
We’re based in the Los Angeles 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 Los Angeles
Yes, in most cases the city will require evaluation and likely retrofit of the soft-story condition before approving a second story addition over a pre-1978 wood-frame garage with tuck-under parking. This falls under the Mandatory Seismic Retrofit Ordinance, and the retrofit scope includes steel moment frames or plywood shear walls at the garage opening. We include this scope in the initial quote so the permit doesn’t stall at the counter. Call (877) 610-1318 and we’ll check your property’s retrofit status before you spend a dollar on design.
A compliant ADU quote in Los Angeles includes seismic evaluation for pre-1978 structures, WUI-compliant roofing and ember-resistant vents if the property is in a Very High Fire Hazard Severity Zone, Hillside Ordinance drainage and retaining wall design if the lot slopes, and a permit and inspection schedule tied to draw milestones. Cheap quotes omit these items and hope for a lenient inspector. Los Angeles inspectors aren’t lenient. Call (877) 610-1318 for a free estimate that shows every required line item in writing.
In many cases, yes, a detached garage conversion does not require a seismic retrofit of the main house unless the garage shares structural elements with the house or the conversion adds a second story above the garage. Each property is evaluated by a structural engineer as part of the permit package. We’ll tell you the answer after one site visit, not after you’ve paid for plans. Call (877) 610-1318 for that free walkthrough.
If your property is in a Very High Fire Hazard Severity Zone, which includes large portions of the Hollywood Hills and other hillside neighborhoods, California WUI code requires Class A roofing, ember-resistant venting, and fire-resistant exterior assemblies on any new ADU or addition. Non-compliant materials trigger a stop-work order and complicate future insurance renewals. We spec compliant materials in every hillside quote because we know the inspector will check. Call (877) 610-1318 and we’ll confirm your zone before you pick finishes.
It can, especially if the addition includes documented seismic retrofit work, WUI-compliant fire-hardening, or roof replacement with Class A materials, because insurers in Los Angeles increasingly require evidence of these upgrades before writing or renewing policies. We provide the documentation from permits and inspections that insurers ask for. Ask anyone on your street or look up the license number yourself. Then call (877) 610-1318 and we’ll talk about your property specifically.
Call Barrett & Sons Construction for Your Los Angeles Home Addition or ADU
Los Angeles is the only major U.S. city where the Mandatory Seismic Retrofit Ordinance legally compels owners of pre-1978 wood-frame soft-story buildings to structurally reinforce tuck-under parking. That mandate directly reshapes any home addition or ADU project touching those buildings, because un-retrofitted soft-story conditions must be corrected before the city will sign off on new attached or above-garage living space. We know this because we’ve done it, repeatedly, in neighborhoods from Highland Park to the San Fernando Valley.
On a hillside lot in Highland Park, our crew took a 1920s Craftsman down to its original foundation to add a detached ADU. The city required full seismic upgrade of the existing house as part of the scope, so we installed plywood shear walls, a new Simpson Strong-Tie moment frame at the garage opening, and brought the whole addition up to current Hillside Ordinance drainage before inspection sign-off. The change order was written, the draw schedule tied to permit milestones, and the final punch list included an ember-resistant vent in the ADU’s crawlspace because the property sits in a Very High Fire Hazard Severity Zone.
That’s how we work in Los Angeles. Scope in writing, allowances in writing, change orders in writing. Permits pulled and inspections signed on every eligible job. A 90-Day Done Right Promise on every contract. Call (877) 610-1318 today for your free estimate. Tom Barrett will answer, or one of his sons will, and we’ll walk your property before we quote a single number.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Los Angeles since 1998.