Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
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AfterTrusted Home Additions & ADU for Los Angeles Homeowners
Our Best Home Additions & ADU in Los Angeles, CA typically run $53,100 to $153,400 for most room additions, with detached ADUs starting around $106,200. We’re Barrett & Sons Construction, founded in 1998 and owner-operated by Tom Barrett, and we’ve spent 29 years building additions and accessory dwelling units across Los Angeles neighborhoods from Eagle Rock to Westchester. This is not a franchise dispatching strangers to your door. Tom and his sons run the crews, every permit gets pulled, and every price change arrives in writing before a single nail moves. Call (877) 610-1318 and a live person answers, day or night.
What Our Home Additions & ADU Service Includes
ADU Design & Permitting
This is where every ADU starts. We handle the architectural drawings, structural engineering, and the full permit package that Los Angeles Building and Safety requires. Tom’s view on permits is simple: the inspector works for you, not for the contractor, and skipping them is how homeowners end up with a finished unit they can’t legally rent or sell. We pull permits on every eligible job and we don’t start framing until the permit card is posted.
Garage Conversion ADU
A garage conversion in Los Angeles typically runs $35,400 to $94,400, and it’s one of the fastest ways to add a rentable unit to a property that already has a garage sitting half empty. We’re seeing a lot of this in neighborhoods like West Adams and Highland Park, and also Home Additions & ADU in Koreatown, where the original garages are too small for modern cars anyway. Our crew handles the structural work, insulation, drywall, plumbing, electrical, and the finished kitchen and bath. The result is a unit you can actually rent, not a garage with a bed in it.
New Detached ADU
A brand new detached ADU in Los Angeles starts around $106,200 and can go well above $259,600 depending on size, foundation conditions, utility runs, and finish level. This is the right move when the main house doesn’t have an attached garage to convert and the lot has the setback room to build. We handle everything from foundation to roof, and we install the same premium materials we’d put in a main house, including Andersen windows and CertainTeed roofing. The allowance that isn’t on paper is a surprise waiting for a date, so every scope line is written before we start.
Junior ADU & Interior Conversion
A JADU is a junior accessory dwelling unit, usually 500 square feet or less, built within the existing walls of the main house. Los Angeles makes this path attractive because it often avoids the impact fees that a full detached ADU triggers. We’ve converted spare bedrooms, dens, and underused sunrooms into legal, rentable JADUs with their own kitchenettes, bathrooms, and private entrances. The permitting path is simpler, but we still pull the permits and get the final sign-off.
ADU Site Prep & Utilities
Before any structure goes up, the site has to be right. That means grading, drainage, foundation excavation, and trenching for sewer, water, power, and sometimes gas. In Los Angeles, the soil varies a lot: parts of the Valley have expansive clay that moves with moisture, and hillside lots in places like Mount Washington or Silver Lake can require retaining walls and deeper footings. We evaluate the site conditions before we quote, so the foundation price on the estimate is the foundation price on the final bill.
Room Additions
A room addition in Los Angeles typically runs $53,100 to $153,400 depending on square footage, whether it’s a single story or a second story, and what kind of foundation work the site needs. The most common additions we build are primary suites, expanded kitchens, family rooms, and home offices. We tie the new roofline into the existing structure so it looks like the addition was always there, not bolted on as an afterthought. Every change order along the way is written and signed before the work happens.
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.
Brands We Service for Home Additions & ADU
For windows and doors on our additions and ADUs, we install Simonton and PGT products, and we’ve worked with both lines long enough to know their lead times, their thermal performance, and which model fits which Los Angeles wall assembly. Simonton’s vinyl lines hold up well against the coastal moisture you get in neighborhoods like Mar Vista and Playa del Rey, and PGT’s impact-rated products make sense for hillside sites with wind exposure. We’re happy to run a written quote for either brand, or for Ply Gem if that’s what your project calls for.
On the roofing side of a new addition or ADU, we typically install GAF or CertainTeed systems, and we’ve completed hundreds of these roofs over 29 years. The choice between the two usually comes down to the slope of the new roofline and what’s already on the main house so the addition matches. Whether you’ve got a brand preference or want us to spec what fits the structure, we’ll give you a written line-item estimate either way.
Signs You Need Home Additions & ADU Right Now
- Your household grew but your square footage didn’t. An extra bedroom or a dedicated home office changes how a house lives, especially when two people now work from home. Adding space almost always costs less per square foot than selling, paying Los Angeles closing costs, and buying a bigger house at today’s rates.
- An aging parent or adult child needs to live closer. An ADU gives them independence with you nearby, and a JADU does it inside the existing footprint. We’ve built dozens of these family ADUs across Los Angeles, and the zoning changes over the last few years have made them more feasible than ever.
- You want rental income from property you already own. Los Angeles rents on a legal ADU regularly cover the construction loan payment with room to spare. The key is building it legally with permits, because an unpermitted unit can’t be advertised as a rental and can come back to bite you at sale time.
- Your garage is dead square footage. If the garage holds boxes and a car that’s too long to fit anyway, converting it into a unit turns a storage liability into income or living space. We handle the full conversion, including the structural reinforcement, insulation, and separate metering.
- The house no longer fits how you live. A primary suite addition, a larger kitchen with a real island, or a family room that fits the whole extended family changes the daily feel of the house. If you’re considering it, the cost to plan is just a phone call and a free estimate.
Our Home Additions & ADU Process - Step by Step
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You call, we talk. A live person answers at (877) 610-1318. We’ll ask about the lot, the house, the type of addition or ADU you’re picturing, and your budget range. If a site visit makes sense, we schedule one, and there’s no trip charge inside Los Angeles County.
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We walk the site and write the scope. Tom or one of his sons comes out to measure, check foundation conditions, look at the utility access, and talk through what’s feasible. You get a written scope and a written line-item estimate. No numbers thrown out over the phone that change later.
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We pull the permits. For every eligible addition and ADU, we prepare the drawings, submit the permit package to Los Angeles Building and Safety, and post the permit card before work starts. The inspector works for you, not for me, as Tom says, and we schedule every inspection that’s required.
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We build, and you see the progress. The crew shows up when we say they will. If a wall has to move or an allowance gets adjusted, you get a written change order with the new price before the work proceeds. No surprise invoices at the end, ever.
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We finish, inspect, and stand behind it. Final inspection gets signed, we walk the whole project with you, and you get the 90-Day Done Right Promise in writing. If something isn’t done right, one call brings Tom back. We’ve stood behind that promise since 1998.
How Much Does Home Additions & ADU Cost in Los Angeles?
A room addition in Los Angeles typically runs $53,100 to $153,400. A garage conversion ADU runs $35,400 to $94,400, and a new detached ADU runs $106,200 to $259,600. Junior ADUs and interior conversions usually land between $59,000 and $118,000 because they reuse existing square footage. What moves the number: square footage, whether you’re building up or out, soil and foundation conditions on your specific lot, utility distances, and the finish level you choose for kitchens and baths. We don’t quote a low number to win the job and then hand you a different bill at the door. Every estimate is line-itemed, and every change is a written change order before work happens. Call (877) 610-1318 and we’ll walk the site and write a real number for your exact project.
Home Additions & ADU Near Los Angeles - Our Service Area
We build additions and ADUs across Los Angeles County, from the Valley through the Westside, downtown, and the South Bay, and we regularly take on projects in Long Beach, Anaheim, Santa Ana, and Paramount. If you’re in one of those communities or anywhere nearby, call and ask, and if you’re comparing estimates, we also serve Home Additions & ADU in San Diego and Home Additions & ADU in San Jose. For everything else we do, start at our home page. Our standing offer: free second opinion on any written estimate, and no trip charge inside Los Angeles County.
Serving Los Angeles, CA - Our Local Coverage Area
We’re based in the Home Additions & ADU in 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.
Frequently Asked Questions - Home Additions & ADU in Los Angeles
A home addition is any new living space attached to or built on your existing lot, whether it’s a room, a suite, or a second story. An ADU is an accessory dwelling unit, which is a self-contained secondary home on the same lot with its own kitchen, bath, and entrance. Both add square footage and value, but ADUs are specifically designed to be rentable or usable as independent living quarters under California law.
Most room additions take 3 to 6 months from permit submission to final inspection, and a detached ADU typically runs 6 to 10 months depending on site work and utility runs. Permitting with Los Angeles Building and Safety usually takes 4 to 8 weeks on top of the construction timeline. We’ll give you a written schedule with your estimate, and we stick to it because the same crew that starts your job finishes your job. Call (877) 610-1318 to get a timeline for your specific project.
A room addition runs $53,100 to $153,400, a garage conversion ADU runs $35,400 to $94,400, and a detached ADU starts around $106,200 and can exceed $259,600. The final number depends on square footage, foundation conditions, utility distances, and finish level. We give you a written line-item estimate before work starts, and any change later is a written change order you approve first. Estimates are free, so call (877) 610-1318 for an exact quote on your property.
We install and service Simonton and PGT windows on additions and ADUs across Los Angeles, and we’ve worked with both brands for years. We know their lead times, their thermal ratings, and which models fit which wall assemblies in our coastal and inland climates. Whether you want Simonton, PGT, Ply Gem, or any other make, we’ll quote it in writing.
If we uncover rot, termite damage, or foundation cracking during construction, we stop and document it before proceeding. You get photos, a written explanation, and a written change order with the fix and the price, and nothing moves forward without your signature. For urgent structural failures unrelated to an active project, call (877) 610-1318 and we’ll get someone to look at it quickly.
Every addition and ADU we build is backed by the 90-Day Done Right Promise, written on the contract, not buried in fine print. If it’s not done right, one call brings Tom Barrett back to make it right, and we’ve honored that promise since 1998. Materials also carry their manufacturer warranties, which we register for you at completion.
Walk your lot and house and make a list of what you need the new space to do, and gather any old surveys or property records you have. Think about how the space will be used five years from now, not just this year, and write down your absolute top budget number so we can design to it honestly. Then call (877) 610-1318 and book a free site walk, and we’ll handle the rest.
Schedule Your Home Additions & ADU Service in Los Angeles Today
If you’re ready to add space, add a rental unit, or just get a real number from a contractor who puts his name on the truck, call Tom Barrett and his sons at (877) 610-1318. We’ll walk your Los Angeles property, write a line-item estimate, and give you a free second opinion on any written estimate you already have. No trip charge inside the county, no pressure, no surprise invoices. A live person answers day or night.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Los Angeles since 1998.