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 La Mirada
Adding square footage or building an ADU in our La Mirada service area usually means one of two situations: your family has outgrown a 1960s ranch floor plan, or you want a rental unit that actually pencils out in Los Angeles County. A detached ADU in La Mirada typically runs $90,000-$220,000, while a home addition lands between $45,000 and $130,000 depending on scope. Those numbers assume the project clears county seismic review, which nearly every structural change here triggers. If you’re weighing options on a slab-foundation ranch near Foster Road or a cul-de-sac off Santa Gertrudes Avenue, call us at (877) 610-1318 and we’ll walk the property with you before you commit to anything.
We’ve worked on enough La Mirada homes to know the Chevron Land floor plans before we open the front door. That matters when you’re pricing an addition and the difference between a smooth permit and a three-month stall comes down to whether your contractor recognized the original shear wall conditions on the first visit.
Why Barrett & Sons Construction Is La Mirada’s Preferred Home Additions & ADU Company
Tom Barrett started this company in 1998 and his sons run the crews. When a La Mirada homeowner calls about a garage conversion on Rosecrans Avenue or a second-story addition in the 90638 ZIP, the person who answers the phone is someone whose name is on the truck. That’s not a slogan. Tom publishes his name, his address, and his license number. You can look all of it up before you sign anything.
Our Home Additions & ADU team has pulled permits and passed inspections on projects across all three La Mirada ZIP codes: 90637, 90638, and 90639. We know which counter plan checkers ask the most questions about post-and-beam retrofits. We know which La Mirada streets still have original cast-iron drain lines because we’ve replaced enough of them to recognize the pattern. And because we’re a local crew, not a franchise dispatching strangers, a call about a punch-list item brings Tom back, not a ticket number.
Every eligible job gets permits pulled and inspections signed. That’s not optional, and it never was. The permit inspector works for you, not for the contractor. We like it that way.
Our Home Additions & ADU Services in La Mirada
Here’s what we actually do in La Mirada, week in and week out. Not every company handles all of this under one roof, and in a city where the housing stock is aging in lockstep, that matters more than people expect. That includes La Mirada Roofing and full exterior work when your project needs it.
ADU Design & Permitting
Most La Mirada ADUs start as a set of drawings that need to clear LA County’s seismic review before anyone swings a hammer. We handle the full design and permit package for detached ADUs, garage conversions, and junior ADUs. Because we’ve done this repeatedly on Chevron-plan lots across 90638 and 90639, we know what the county reviewers will flag and we address it before the first submittal. That saves weeks. A typical ADU design and permit package in La Mirada runs $8,000-$20,000 of a larger project budget.
Garage Conversion ADU
La Mirada’s original 1960s garages were built on the same poured slabs as the houses, which is good news for conversion work. The slab is already there. The challenges are the ones we see everywhere in this city: 100-amp electrical panels that can’t support a second dwelling unit, original drain lines that need scoping, and low-slope garage rooflines that need membrane replacement while the crew is in there anyway. We also handle Windows & Doors - La Mirada upgrades when the conversion calls for them. A garage conversion ADU in La Mirada typically runs $30,000-$80,000 depending on whether you’re doing a studio or a one-bedroom with a full kitchen.
New Detached ADU
When there’s room in the rear yard and you want a fully separate unit, we build new from the slab up. In La Mirada, rear-yard setbacks vary by lot, and many of the original Chevron tracts have oddly shaped parcels that require creative footprints. We’ve built detached ADUs behind ranch homes near La Mirada Regional Park and along the streets off Imperial Highway. A new detached ADU here runs $90,000-$220,000, with the spread driven mostly by square footage, finishes, and whether you want a kitchen with stone counters or something simpler.
Junior ADU & Interior Conversion
A JADU is the fastest, least expensive way to add a legal rental unit in La Mirada. You’re converting existing interior space, often a attached garage bay, a den, or part of a large primary bedroom, into a small self-contained unit. These projects stay under the county’s 500-square-foot JADU cap and typically don’t require the same level of fire sprinkler upgrades. A junior ADU in La Mirada can often be completed for $40,000-$90,000, and because the work is inside the existing envelope, the permit path is shorter than a detached build.
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 La Mirada
When exterior work is part of the scope, we like products our customers can look up before they buy. For driveway approaches, walkways, and patio areas that often accompany ADU entries, we install Belgard and Techo-Bloc pavers. For concrete work tied to slab additions or trenching for utilities, we use Quikrete products we can get locally the same day. We’re not putting mystery materials off the back of a van on a La Mirada addition. Materials get named in the written scope before we order them, and pricing for allowances goes in writing too. An allowance that isn’t on paper is a surprise waiting for a date.
Common Home Additions & ADU Problems We See in La Mirada Homes
- Original 100-amp electrical panels. Nearly every La Mirada ranch built between 1959 and 1968 came with an undersized panel that cannot carry a modern addition plus an ADU. We plan for panel replacement in the initial scope, not as a surprise change order.
- Cast-iron and galvanized drain lines. The original plumbing under La Mirada slab foundations is reaching end of life. When we open a slab for new plumbing runs, we scope the existing lines and factor replacement into the written estimate if it’s needed.
- Low-slope and flat roof sections on original ranch homes. La Mirada’s inland summer heat, with regular mid-90s days, bakes roofing membranes. When an addition ties into an existing low-slope section, we check membrane condition and include replacement if the original material is spent.
- Seismic shear wall retrofits required on structural work. Because La Mirada sits near the Whittier Fault corridor, LA County reviewers require shear wall and foundation tie-down upgrades on most permitted additions and structural ADU conversions. A contractor who doesn’t know this will underbid the job and hit you with a change order later.
Pricing for Home Additions & ADU in La Mirada, CA
Here’s what honest numbers look like in La Mirada right now. A room addition on a 1960s ranch home runs $45,000-$130,000 depending on square footage and whether you’re adding a bathroom. A full detached ADU runs $90,000-$220,000. A garage conversion ADU runs $30,000-$80,000. A junior ADU or interior conversion runs $40,000-$90,000. ADU design and permitting as a standalone scope runs $8,000-$20,000.
What moves the number most in La Mirada is what we find under the slab and behind the walls of a house built in the early 1960s: electrical panels, drain lines, and roof tie-in conditions. That’s why we put every scope and every allowance in writing before work starts. You’ll see the price in a written line-item estimate, and if anything changes, you’ll see a written change order before that work begins. No surprise invoices. Call (877) 610-1318 for a free estimate and we’ll give you real numbers for your specific house.
We Also Serve Cities Near La Mirada
While most of our Home Additions & ADU work in this area is within La Mirada’s three ZIP codes, we also take projects in South Whittier, East La Mirada, Buena Park, and Norwalk. For homeowners on the northern edge of the city looking at Kitchen Remodeling in La Mirada or a Bathroom Remodeling in La Mirada along with an addition, we coordinate the full scope under one crew and one set of permits. And if you’re in the surrounding communities and want to know whether we serve your street, the answer starts with a phone call.
Serving La Mirada, CA - Our Local Coverage Area
We’re based in the La Mirada 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 La Mirada
Most La Mirada ADU projects run 6 to 12 months from the first site visit to final inspection, with county permit review typically taking 8 to 16 weeks depending on project type and review load. A JADU can move faster. A detached ADU with new utilities and a new slab takes the longest. We’ll give you a written timeline with your estimate, and we call out the permit-review window separately so you know what’s in our control and what isn’t. Call (877) 610-1318 to talk through your timeline.
Yes, we pull permits and coordinate inspections for ADU and home addition projects across all three La Mirada ZIP codes: 90637, 90638, and 90639. That includes the neighborhoods near La Mirada Regional Park, the streets off Foster Road and Santa Gertrudes Avenue, and the original Chevron tracts throughout the city. Structural work on La Mirada’s 1960s ranch homes almost always triggers county seismic review, so we build that review time into the schedule from day one.
It won’t change without your written approval. Every price change at Barrett & Sons comes as a written change order before the work happens. If we open a wall and find something the original builder hid, you’ll see it in writing with a number attached before a nail moves. That’s the whole reason we put scope in writing, allowances in writing, and change orders in writing. The numbers in your original estimate are the numbers we stand behind.
La Mirada ADU pricing is generally in line with Los Angeles County norms, but three local factors move the number: the uniform 1960s housing stock with predictable electrical and plumbing deficiencies, the county seismic compliance review that applies to structural work here, and lot configurations on the original Chevron tracts that sometimes push ADUs toward custom footprints. Expect a detached ADU at $90,000-$220,000 and a garage conversion at $30,000-$80,000. For an exact number on your property, call (877) 610-1318 and we’ll come out.
Yes. Every completed job in La Mirada carries our 90-Day Done Right Promise, written on the contract. If something’s not done right, one call brings Tom Barrett back to make it right. We’ve been standing behind our work since 1998, and we live close enough that coming back isn’t a favor, it’s the job. Ask anyone on your street, or look up the license number.
Get Your Free La Mirada Home Addition or ADU Estimate
If you’re thinking about an addition or ADU on a La Mirada property, start with a conversation and a walkthrough. We’ll give you real numbers, a written scope, and a straight answer about what your 1960s house will need. Call (877) 610-1318 to schedule your free estimate. Tom and his sons answer the phone.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving La Mirada and surrounding Los Angeles County communities since 1998.