A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateADU Company in Costa Mesa, CA
An ADU (accessory dwelling unit, or a second smaller home built on your existing lot) in Costa Mesa usually costs between $180,000 and $420,000 for a detached unit, and $120,000 to $260,000 for a garage conversion. Costa Mesa homes are mostly 1950s and 1960s ranch builds with wood frames, stucco exteriors, and slab foundations, which means almost every project involves electrical panel upgrades and foundation work before framing starts. We’re Lodgewick ADU Orange County, part of the Kingswell family, and we put the full price in writing before any work begins. Call (350) 203-6060 to talk through your lot.
Why Costa Mesa Homes Are Different
Costa Mesa’s Eastside and Westside neighborhoods are dense with single-story ranch homes sitting on lots between 6,000 and 7,200 square feet. Those tighter lots make ADU placement a real puzzle. State lot-split rules under SB 9 and Costa Mesa’s two-unit ADU allowances open the door for detached units behind the garage, but narrow 10-foot side setbacks and rear alley access mean the city reviews each project case by case. A plan that works on paper often shifts once the planner sees the driveway geometry.
The homes themselves bring their own complications. Original 100-amp electrical panels are common, and a new ADU almost always triggers a panel upgrade to 200 amps. Many houses still run galvanized plumbing that needs replacement at the tie-in. The coastal air is another factor: morning marine layer means fog-driven dampness sits on exterior walls, so we spec moisture-resistant siding and flashing details that a standard inland build wouldn’t need. If your lot sits in College Park or Mesa Verde, the rear alley access can flip a simple garage conversion into a full site redesign when the city questions whether the alley meets modern fire-truck turning radius standards.
Our Main Costa Mesa Services
Costa Mesa homeowners call us about three things most often: adding square footage to the main house, converting an attached garage into living space, and building a detached ADU in the backyard. Each one has its own Costa Mesa page with full pricing and detail.
Home Addition Contractor in Costa Mesa
A home addition in Costa Mesa means working around slab-on-grade foundations and mature trees that have spent fifty years spreading roots under the yard. We handle the structural tie-in, roof integration, and the panel upgrade that nearly every 1960s ranch requires before it can carry new load. This is where the written price matters most – additions have the widest cost range in this city, and a vague estimate can double once the foundation gets opened. Home Addition Contractor in Costa Mesa has the full breakdown, including what foundation work costs on Eastside lots.
Garage Conversion Contractor in Costa Mesa
A garage conversion (turning an existing attached or detached garage into a legal living space) is the fastest route to an ADU in Costa Mesa. The structure already exists, which saves foundation and framing costs. But the city’s replacement parking rules can get tricky, especially in College Park and Mesa Verde where rear garages face 20-foot alleys. If the alley can’t support modern fire-truck access, the city may not grant the replacement parking credit, and the project scope changes. Garage Conversion Contractor in Costa Mesa covers exactly how that plays out on your street.
ADU Builders in Costa Mesa
A detached ADU in a Costa Mesa backyard is a full ground-up build: foundation, framing, utility trenching, and a separate meter or subpanel. The 10-foot side setbacks on Eastside and Westside lots push units closer to rear property lines, which changes egress and window placement. We also work with prefab ADU manufacturers like Abodu, Cover, and Dvele when a factory-built shell fits the site better than stick framing. ADU Builders in Costa Mesa has the numbers for both prefab and site-built units.
What happens when you call
- 1
A real person answersNo phone trees - you reach a local pro.
- 2
You get an upfront price rangeHonest numbers before anyone is dispatched.
- 3
A background-checked tech heads outLicensed & insured, dispatched right away.
- 4
You approve before work beginsNothing starts until you say go.
Brands We Service in Costa Mesa
Costa Mesa homeowners who choose prefab often ask about Abodu and Dvele for faster site assembly, and Cover for designs that work on narrow Eastside lots. We handle the site work, foundation, utility connections, and city approvals for all of them. See our brands for the full list of manufacturers we support.
Pricing for ADU Company in Costa Mesa, CA
| Service | Typical range in Costa Mesa |
|---|---|
| Detached ADU (one-bedroom, site-built) | $180,000 – $260,000 |
| Detached ADU (two-bedroom, site-built) | $260,000 – $420,000 |
| Garage conversion (attached, one-bedroom) | $120,000 – $180,000 |
| Garage conversion (attached, two-bedroom) | $180,000 – $260,000 |
| JADU (junior ADU inside existing footprint) | $80,000 – $140,000 |
| Prefab ADU (factory-built shell, installed) | $160,000 – $320,000 |
| Home addition (family room or primary suite) | $150,000 – $350,000 |
| Electrical panel upgrade (100-amp to 200-amp) | $3,500 – $6,000 |
Costa Mesa pricing pushes upward when the job includes a panel upgrade, galvanized pipe replacement, or a site redesign tied to alley access rules. Every Lodgewick project gets a written price before work starts, so the number you approve is the number you pay.
Neighborhoods We Serve in Costa Mesa
We work across Costa Mesa, and most of our ADU and addition builds are in the neighborhoods with older ranch stock and larger backyards. A representative sample:
- Eastside Costa Mesa
- Westside Costa Mesa
- College Park
- Mesa Verde
- Freedom Homes / Halecrest
Response time for estimates in Costa Mesa is typically one to two business days, depending on how many site visits are already on the schedule that week.
Service Area – Cities Near Costa Mesa
We also serve homeowners in the surrounding Orange County communities where the housing stock and lot patterns are similar. If you’re in Santa Ana, CA, Midway City, CA, Tustin, CA, or Anaheim, CA, the same written-price guarantee applies to your project. Scheduling and dispatch are coordinated from our Los Angeles office, but the crews and site visits happen locally in Costa Mesa.
Serving Costa Mesa, CA - Our Local Coverage Area
We’re based in the Costa Mesa 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 About ADU Company in Costa Mesa
Most detached ADUs in Costa Mesa take 8 to 14 months from permit application to final inspection. Garage conversions run faster, typically 4 to 8 months. City plan review and any lot-split or alley-access questions add time. Call (350) 203-6060 and we’ll give you a realistic timeline for your specific street.
Some Costa Mesa neighborhoods have HOAs with their own design review on top of city permits, especially in Mesa Verde and certain Eastside tracts. We pull city permits and handle the HOA paperwork if your community requires it. The timeline depends on how often your HOA board meets. Call (350) 203-6060 to check what applies to your lot.
No. The Kingswell Guarantee means the written price you approve is the price you pay, with no change orders at the door. If site conditions uncover something unexpected, we stop and put the revised cost in writing before proceeding. Call (350) 203-6060 for a free written estimate on your Costa Mesa project.
What happens when you call
- 1A real person answersNo phone trees - talk to a local adu pro.
- 2You get an upfront price rangeHonest numbers before anyone is dispatched. No surprises.
- 3We come out and measureLicensed & insured, at a time that suits you - the visit and the quote are both free.
- 4You get the price in writingLine-itemed, yours to keep, and nothing starts until you say go.
What Costa Mesa Customers Say
"Junior ADU conversion inside the house. They protected the rest of our place with plastic and daily cleanup. Done nearly on schedule and on the number they quoted."
- Sabrina Veld"I was nervous about adding on but they walked me through every step and every cost before we started. No surprise change orders halfway through like I'd heard horror stories about."
- Eleanor Pratt"Added a suite for my dad. They walked us through every cost before a hammer swung and stuck to it. The written price is what we paid, no change orders."
- Ingrid Salazar
