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
Adding square footage in Los Angeles isn’t a simple framing job. Between hillside grading rules, the city’s seismic retrofit mandates, and Department of Building & Safety plan checks that can stretch for months, most homeowners hit a wall before the first permit is even pulled. A new room addition or ADU in Los Angeles typically runs $53,100 to $153,400 depending on scope, site conditions, and whether you’re converting existing space or building new from the slab up. Our crews know which hillside inspectors require geotech reports, which soft-story retrofits can piggyback onto an ADU permit, and how to sequence a garage conversion so you’re not living in construction dust for a year. Call Barrett & Sons Construction at (877) 610-1318 and we’ll walk your property, look at the lot lines and the hillside, and tell you honestly what’s buildable and what the city will want from you before we ever discuss a contract.
Why Barrett & Sons Construction Is Los Angeles’s Preferred Home Additions & ADU Company
We’re not a franchise with a call center in another state. Barrett & Sons Construction was founded in 1998 by Tom Barrett, and Tom’s sons run the crews. When a project in Los Angeles needs a decision, the person making it is someone whose name is on the side of the truck and who lives close enough to drive by your site on a Saturday. Tom publishes his name, address, and license number. Look it up before you sign anything.
Los Angeles homeowners tell us the same story again and again: a contractor promised permits, then asked for cash mid-project to “expedite” things. We pull permits on every eligible job and we wait for the inspector to sign before we call it done. Every scope change, every allowance, every price adjustment comes to you as a written change order before a single nail moves. The permit inspector works for you, not for us. That’s why we like him.
We answer our own phone, 24 hours a day. You won’t get a voicemail tree or a dispatcher reading from a script. You’ll get a live person who can pull up your Los Angeles project file and tell you where things stand. That matters when a building inspector asks a question mid-week and the clock is running.
Our Home Additions & ADU Services in Los Angeles
ADU Design & Permitting
Most Los Angeles ADU projects stall at the permit counter, not the jobsite. The city has its own ADU ordinance layered on top of state law, and what’s allowed in a flat Mid-City lot can be completely different from what’s allowed on a hillside in Silver Lake. We handle the full design and permitting path: site surveys, plan sets that actually match how we build, geotech where the hillside requires it, and submittal packages that don’t bounce back for missing details. The ADU Construction cost in Los Angeles runs $106,200 to $259,600 for a new detached build, and getting the permit package right from day one is what protects that budget.
Garage Conversion ADU
Converting an existing garage is usually the fastest, most cost-effective ADU route in Los Angeles, especially in neighborhoods like Koreatown and Echo Park where the original garages are oversized and structurally sound. A garage conversion in Los Angeles typically runs $35,400 to $94,400. We handle the structural work the city actually requires: foundation inspection, ceiling height corrections, insulation, fire separation, and the seismic upgrade triggers that come with converting a pre-1978 structure.
New Detached ADU
Building a new detached ADU in Los Angeles means working against three constraints at once: lot coverage limits, setback codes, and hillside grading rules if you’re in the Santa Monica Mountains or the Hollywood Hills. A new detached ADU on a flat lot in the San Fernando Valley is a very different job from one on a sloped lot in View Park-Windsor Hills. We handle site prep, foundation, utility trenching, and the full build, and we’ll tell you early if your lot’s geology is going to add geotech costs before you’re committed.
Junior ADU & Interior Conversion
A junior ADU, or JADU, is the most affordable way to add rentable square footage in Los Angeles: it converts existing interior space, usually a bedroom or a bonus room, into a self-contained unit with its own entrance, kitchenette, and bath. JADUs range widely depending on whether you’re converting a finished room or stripping to studs, but the smaller footprint and no-new-foundation path is why so many Los Angeles homeowners start here. We also handle Kitchen Remodeling in Los Angeles when the JADU needs a kitchenette built from scratch, and Bathroom Remodeling in Los Angeles to bring the new bath up to code.
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.
Common Home Additions & ADU Problems We See in Los Angeles Homes
- Pre-1978 construction triggering seismic retrofit requirements. Los Angeles’s Mandatory Seismic Retrofit Ordinance targets soft-story and non-ductile concrete buildings, but even single-family additions on older foundations often trigger structural upgrades the homeowner didn’t expect. We identify these early so the cost is on paper before demo starts, not a surprise at framing inspection.
- Hillside drainage and slope stability issues that only show up in wet years. Los Angeles gets most of its rain in a few intense atmospheric river events, and drainage problems hide during dry years. A room addition on a hillside lot in Bel Air or the Hollywood Hills needs site drainage designed for the worst season, not the average one.
- WUI fire code requirements in Very High Fire Hazard Severity Zones. Parts of Los Angeles, especially hillside neighborhoods, sit in zones that require Class A roofing, ember-resistant vents, and fire-resistant exterior materials on any addition or new ADU. These aren’t optional upgrades; they’re code. We build them into the design and the price from the start.
- Utility capacity that can’t handle the extra load. Older Los Angeles homes, from 1920s Craftsman bungalows in Highland Park to post-war ranch homes in the Valley, often have electrical panels and sewer lines that can’t legally serve a new ADU or bedroom addition. We inspect and upgrade the service so the addition doesn’t buckle the existing systems.
Pricing for Home Additions & ADU in Los Angeles, CA
A home addition in Los Angeles runs $53,100 to $153,400. The bottom of that range is a modest single-room addition on a flat lot with easy access. The top is a multi-room second-story addition or a larger ADU with new foundation, upgraded electrical service, and hillside grading. A new detached ADU in Los Angeles runs $106,200 to $259,600. A garage conversion runs $35,400 to $94,400. What moves the number: slope, soil, access for equipment, the age of your existing electrical panel, and whether the city’s fire zone requirements apply to your lot. We give you a written line-item estimate before you sign anything, and every change order during the build is written and priced before we proceed. Call (877) 610-1318 for an exact quote. Estimates are free, and we’ll walk the lot with you and explain what’s driving the number.
Trusted Brands We Service in Los Angeles
Barrett & Sons Construction is our Home Additions & ADU team, and the materials we install are brands you can look up yourself. We use Techo-Bloc and Cambridge Pavers for hardscape and entry elements on Los Angeles ADU projects where outdoor space is part of the plan, and we’ll tell you upfront if a specific paver or finish is backordered so you’re not waiting three months for a color that’s out of stock. We keep familiar product lines moving through our Los Angeles area suppliers, which helps keep lead times from dragging out when the city is already slow to approve.
We Also Serve Cities Near Los Angeles
Our crews serve the whole Los Angeles metro, including neighborhoods from Echo Park to Silver Lake, Koreatown to View Park-Windsor Hills. If you’re in one of those pockets and wondering whether we’ll drive out for your addition or ADU, the answer is yes. This is our local service area and we know the inspectors, the lot patterns, and the code interpretations that vary from one Los Angeles neighborhood to the next. We’re a Home Additions & ADU in Los Angeles company, full stop.
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
A home addition in Los Angeles typically costs $53,100 to $153,400 depending on the size of the addition, whether it’s a first-floor bump-out or a second-story build, the slope of your lot, and the age of your existing foundation and electrical systems. A new detached ADU runs higher, typically $106,200 to $259,600. The biggest cost drivers in Los Angeles are hillside grading, fire zone material requirements, and the structural upgrades the city’s retrofit ordinance can trigger on older homes. Call (877) 610-1318 for an exact quote on your specific lot. Estimates are free.
Yes, for garage conversions and some interior ADUs, the work can be sequenced so the existing tenants stay in place during the build. Los Angeles’s soft-story retrofit ordinance has made this a specialized trade, and our crews know how to organize steel moment frame or shear wall work so the primary structure is reinforced without vacating the units above. Tenant displacement restrictions are part of Los Angeles’s rent control and just-cause eviction landscape, so the construction schedule has to be planned around them from the start.
Plan for four to eight months on the permit side for a new detached ADU in Los Angeles, depending on your lot and whether the hillside ordinance triggers geotech review. Garage conversions and JADUs that stay within existing walls usually move faster, but the city’s plan check queue is what it is, and the turnaround depends heavily on how clean the submittal package is. We front-load the design and documentation so your project doesn’t bounce back for corrections. Call (877) 610-1318 and we’ll give you an honest timeline for your neighborhood and lot type.
Yes, the 90-Day Done Right Promise is on every Barrett & Sons Construction contract, including full room additions and new ADU builds. If something isn’t right after completion, one call brings Tom back to make it right. It’s not buried in fine print; it’s written on the front of the contract for a reason.
Yes, and we won’t start without them. Los Angeles requires permits and inspections for any structural addition or ADU conversion, and the consequences of skipping them include fines, stop-work orders, and problems when you eventually sell the house. We pull permits on every eligible job and we wait for the final inspection before we call the project done. The inspector works for you, not for us, and we wouldn’t have it any other way.
Call Barrett & Sons Construction for Your Los Angeles Home Addition or ADU
If you’re thinking about adding square footage in Los Angeles, the first step is a free estimate and a straight answer about what your lot can support. Call Tom and his team at (877) 610-1318 to schedule a walkthrough. We’ll look at the slope, the setbacks, the existing foundation, and the city’s requirements for your specific neighborhood, then hand you a written line-item quote. No pressure, no mystery pricing, no permits skipped. Just a clear path from where your Los Angeles home is now to where you want it to be.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Los Angeles since 1998.