A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateTrusted ADU Builders for Orange County Homeowners
Most Orange County homeowners who come to us have a lot in their back 40 percent already permitted for an ADU and a folder full of contractor bids they don’t trust. They’ve been burned by a guy who disappeared after demo, or a bid that came in 40 percent light. Fielding ADU Builders fixes that with a written price before any work starts and a 365-day written guarantee on every build. Reed Calloway, who heads Fielding ADU Orange County, has been building to The Garrison Standard since 2006, and every crew member on your site is background-checked and in uniform. Call (424) 577-4306 for a free estimate.
ADU Construction
ADU Construction means building a fully permitted secondary dwelling on a residential lot, either attached to the main house, converted from an existing garage, or built as a freestanding structure. In Orange County this typically runs $180,000 to $420,000 for conventional construction before permit and impact fees, with prefab units often landing between $120,000 and $280,000 before site work. We handle the whole job: plans, structural engineering, permits, foundation, utilities, and finish work, all backed by a written one-year guarantee. Reed Calloway’s crews have built these through Tustin and Santa Ana where setbacks and lot coverage can eat a design before it starts.
Permitted Construction From Day One
We pull permits on every ADU project, no exceptions. The permit board goes up before the first excavation, and it stays up until the city signs off on final inspection. If a homeowner wants to skip permits to save a few thousand dollars, we decline the job; unpermitted ADUs in Orange County create title problems when you sell and can trigger fines from code enforcement.
Utility Connections Done Right
Most lots in Fountain Valley and Aliso Viejo have sewer lateral and electrical panel capacity questions that a cheap bid simply ignores. We verify capacity up front so you’re not hit with a surprise $15,000 panel upgrade after the footing is poured. The written price covers what we say it covers, and we flag anything outside the scope before it becomes a change order.
Detached ADU
A Detached ADU is a standalone unit separated from the main house, built in the rear or side yard, with its own entrance, kitchen, bath, and utility connections. In Orange County, a detached unit with standard finishes typically runs $220,000 to $460,000 before permitting fees, and we complete most in five to seven months once city approvals are in hand. Detached units are the most common choice in Newport Beach and Ladera Ranch where lot sizes allow the separation and homeowners want true rental privacy. We build them conventionally with James Hardie siding or as prefabricated units from Abodu and Cover, depending on what the lot and budget justify.
Prefab Detached Units
For a tighter timeline, we work directly with Abodu, Cover, Dvele, and Mighty Buildings on detached ADUs. The unit arrives factory-built and we handle the site work: foundation, utilities, grading, and the final city inspection. Homeowners in Rancho Santa Margarita have used this route when they wanted a one-bedroom rental unit finished inside four months.
Conventional Detached Builds
When the lot is narrow or the city requires custom setbacks, a conventional stick-built unit gives us full control of dimensions. We frame on site, match the main house’s roof pitch where the city requires it, and finish with James Hardie fiber cement siding so the unit holds up against Orange County’s coastal salt air and inland heat. The written price stays fixed from approval to final walkthrough.
JADU
A JADU, or Junior Accessory Dwelling Unit, is a small self-contained unit created entirely within the walls of an existing home, capped at 500 square feet under California law, often converted from an attached garage or a master suite wing. In Orange County, JADU conversions typically run $80,000 to $150,000 before permit fees, making them the lowest-cost way to create a rentable unit on your lot. They’re popular in Laguna Woods and Rossmoor where lot space is tight and homeowners want a caregiver suite or rental income without a backyard build. Fielding ADU Orange County handles the full conversion: separate entrance, kitchenette, bath, and the fire separation the code requires.
Garage-to-JADU Conversions
An attached garage in North Tustin or Tustin already has the foundation and exterior walls in place, which trims thousands from the budget. We add the required insulation, drywall, egress, and a compact kitchen and bath, then pull the permits and pass the inspections. The Garrison Standard applies the same as on a full detached build: written price, clean job site, and a full year of written guarantee.
Code Separation and Kitchen Requirements
A JADU needs its own entrance and a kitchenette with a cooking appliance, and the city will check fire separation between the unit and the main house. We handle that separation correctly the first time, and if the inspector flags something we show back up within the year and fix it at no charge. That’s the Done Right Promise in plain terms.
ADU Plans
ADU Plans are the architectural drawings, structural calculations, and site plans that the city’s building department reviews before it issues a permit, and getting them right is where most ADU projects in Orange County stall or fail. Plan sets and engineering typically run $4,000 to $12,000 depending on lot complexity, and we include them in our written project price rather than nickel-and-diming you for revisions. A plan that misses a side-yard setback in Orange or a fire sprinkler requirement in Santa Ana costs weeks of delay; our plans are drawn to the city standard the first time.
Setback Variance Drawings
When your lot is under 5,000 square feet and you want to build closer to the property line than the standard rule allows, the city needs a setback variance, which is simply written permission to build closer to the line. We prepare those drawings and the supporting documentation, then walk them through the planning counter. In older Orange County neighborhoods built before modern setback rules, this is often the difference between a buildable ADU and no ADU.
Tidelands, Slope, and Overlay Checks
Some Orange County parcels in Fountain Valley and Newport Beach carry overlay zones, floodplain notes, or slope conditions that a generic online plan set won’t catch. We pull the title report and check the lot against city overlays before a single plan line is drawn. If the lot won’t support what you want, we tell you in the first meeting, not after you’ve paid for plans.
ADU Contractor
An ADU Contractor is the licensed general contractor who carries the project from excavation to final inspection, and choosing the right one in Orange County comes down to price integrity and follow-through. Fielding ADU Orange County puts the full price in writing before work begins, and the number you approve is the number on the final invoice. We’re not the cheapest bid in Orange County, and we don’t try to be. Homeowners who call us after a cheaper contractor walked off a job in Ladera Ranch tell us they’d rather have known the real number up front.
Written Price, No Change Orders
Garrison Partners has built to The Garrison Standard since 2006, and the core of that standard is the written price. If the job scope changes because you ask for something different, we write the change order and you approve it before we proceed. You will never find an “unforeseen condition” line item slipped into the invoice at the end.
Background-Checked Crews on Your Property
Every worker on your ADU project has passed a background check before they set foot on your lot, and they arrive in uniform. You know who is on your property every morning, and you can reach a live person by phone at noon or midnight if something comes up. That phone policy has been in place since day one, and we don’t route you to a voicemail queue.
ADU Design
ADU Design is the process of shaping the unit’s floor plan, roofline, and finishes around your lot’s actual constraints and the city’s actual rules, and in Orange County that process determines the final cost more than anything else. Design work typically runs $3,000 to $9,000 when bundled with plans and engineering, and we fold it into the written project price. A poorly designed ADU in Rancho Santa Margarita with plumbing on the wrong side of the unit can add $8,000 in trenching; a well-designed one keeps the wet wall shared and the build simple.
Lot-First Design Reviews
Before we draw a concept, we walk the lot in Orange County with a tape measure and a city checklist. We check access for excavation equipment, overhead utility clearances, drainage flow, and the distance from the main panel. If a backyard ADU won’t work because the lot slopes hard toward Aliso Creek in Aliso Viejo, we’ll tell you in the first call and steer you toward an attached conversion instead.
Design-Build Without the Surprise Bids
Because we’re a design-build contractor, the designer and the builder sit in the same room, so the plan that gets drawn is a plan we can actually build for the written price. You won’t get a beautiful set of drawings from one firm and three wildly different bids from builders who each want to redesign it. That single point of responsibility is why homeowners in Tustin and North Tustin keep coming back for second units.
Backyard ADU
A Backyard ADU is a detached unit built in the rear yard, away from the main house, with its own entrance and private outdoor space, and it’s the most requested build type we handle in Orange County. Depending on size and finish level, backyard ADUs here run $220,000 to $460,000 before permit and utility fees, with prefab backyard units from Cover or Dvele often landing in the $150,000 to $300,000 range before site work. They work well on the deeper lots common in Newport Beach and Ladera Ranch, where the unit can sit behind the house and still leave a usable yard.
Prefab Backyard Units That Ship Ready
For homeowners who want a backyard ADU fast and clean, we work with Cover and Dvele on units that arrive pre-built and get craned or rolled into place. We pour the foundation, stub the utilities, and handle the final connections and inspection. The site work is priced the same way every other Fielding job is priced: in writing, up front.
Site Work That Most Bids Hide
A backyard ADU is not just the box; it’s the trenching for power and water, the sewer tie-in, the grading, and the retaining wall if the yard pitches. Those are the line items where cheap bids go soft in Orange County, and they’re exactly the line items we write down before work starts. If your yard in Rossmoor drains toward the house, we’ll catch it in the walk-through and price the correction so it doesn’t hit you at the end.
Brands We Service
We work directly with Abodu, Cover, Dvele, and Mighty Buildings, which means we know the site requirements, utility hookups, and city inspection paths for each platform before the unit ever arrives. An Abodu unit, for example, ships with specific electrical and plumbing rough-in locations, and we set the foundation and stubs to match those specs so the crane day doesn’t turn into a two-week delay. We’ve built the site work for Cover units on tight lots in Orange where the factory tolerance was an inch, and the unit still landed square.
Dvele units come with high-performance envelope systems already sealed, and Mighty Buildings panels arrive flat-packed for on-site assembly. We handle the foundation, the utilities, the final cladding where needed, and the city sign-off on every one of these. Whether you’re leaning toward a prefab unit or a conventional build with James Hardie siding, we can match the right method to your budget and your lot. If you already own a prefab unit from any of these brands, we’ll handle the site work and inspections too.
Signs You Need a Pro Right Now
- Your city sent a code enforcement notice. If Orange County code enforcement has flagged an existing unpermitted unit on your property, you need a contractor who can file the permits, fix the violations, and bring the unit to current code. Waiting doesn’t make the notice go away, and fines accrue monthly in some cities.
- Your plans came back from the city with redlines. If the Orange County planning department bounced your plan set over a setback, an overlay zone, or a missing structural calc, a designer who doesn’t know the local standard can burn months in resubmittals. We redraw and resubmit, and we’ve cleared plan checks in Santa Ana and Orange first pass.
- A previous contractor walked off mid-build. If you have a half-framed ADU in Ladera Ranch or Tustin and a contractor who stopped answering the phone, you need a builder who will inspect the work, document what’s salvageable, and finish the job with a written price. We take on orphaned projects and put the permit back in order.
- Your main panel can’t carry the load. If an electrician told you an ADU on your lot in Fountain Valley needs a panel upgrade before the city will pass inspection, we can scope that work and price it in the written estimate. Ignoring the panel just moves the problem to final inspection, where it costs more to fix.
- You need rental income and you need it on a deadline. If you’re building an ADU in Newport Beach to house a family member or rent out by a certain date, a contractor who misses the schedule costs you real money in lost rent or a second lease extension. The Garrison Standard stands behind a written schedule and a written price, and we finish what we start.
Our Process, Step by Step
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Call and talk to a person. When you call (424) 577-4306, a live person answers, day or night, and schedules your free on-site walk-through. We’ll ask about your lot, your goals for the unit, and whether you already have plans or need them.
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On-site walk-through and lot check. Reed Calloway or a senior project lead walks your property in Orange County and checks the things that kill budgets later: access, drainage, panel capacity, sewer depth, and city overlay zones. You’ll hear the truth about your lot on this visit, even if the truth is that a JADU makes more sense than a backyard ADU.
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Written price in your hand. After the walk-through, we deliver a written price covering the full scope: plans, permits, construction, finishes, and site work. The number you approve is the number on the final invoice, and if something outside the scope appears, we write it down and get your sign-off before spending a dollar.
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Permitting and construction. We file the plans, pull the permit board, and run the job in a sequence that protects your property and your neighbors. Every crew member on site is background-checked and in uniform, and the site is left clean at the end of each day. We schedule inspections and fix any corrections the city flags.
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Final walkthrough and the written guarantee. When the city passes final inspection, we walk the unit with you and hand over the written one-year guarantee. If something fails inside that year, we come back at no charge and make it right. That’s the Done Right Promise, and it’s been the standard since 2006.
How Much Does ADU Builders Cost in Orange County?
A conventional detached ADU in Orange County typically runs $220,000 to $460,000 before permit and utility fees, a garage conversion or attached JADU runs $80,000 to $180,000, and a prefab unit from Abodu, Cover, Dvele, or Mighty Buildings lands between $120,000 and $300,000 before site work. Plan sets and engineering add $4,000 to $12,000, with design work folded into the written price. These are true ranges for this market, not national averages; Orange County plan check fees, impact fees, and local labor rates push the numbers higher than you’ll see on a generic online calculator.
What moves the price is lot access, sewer depth, panel capacity, and whether the city requires fire sprinklers, side-yard setbacks, or an overlay review. The way to avoid overpaying is to get a written price that includes the site work line items most bids leave hollow, then compare the total, not the square-foot guess. A free estimate from us covers the walk-through, the lot check, and the written price, so call (424) 577-4306 and get the real number for your specific lot before you commit to anything.
Our Service Area Near Orange County
Fielding ADU Orange County serves the full Orange County area, including Santa Ana, Orange, Newport Beach, Fountain Valley, Aliso Viejo, Rancho Santa Margarita, Ladera Ranch, Laguna Woods, Rossmoor, Tustin, and North Tustin. If you’re not sure whether your lot qualifies or which city rules apply, start with our ADU Builders in Orange County page for the region-level guidance, or see our city-specific pages for ADU Builders in Santa Ana and ADU Builders in Orange. For the broader picture, return to the home page.
Serving Orange County, CA - Our Local Coverage Area
We’re based in the Orange County 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 About ADU Builders in Orange County
ADU Builders refers to the general contractor who designs, permits, and builds accessory dwelling units on residential lots, handling everything from foundation to final inspection. In Orange County, this work includes detached backyard units, garage conversions, and JADUs, all of which require city permits and final sign-off. Fielding ADU Orange County has built these units since 2006 under The Garrison Standard, and every project gets a written price before work starts.
Plan for five to seven months from permit approval to final inspection on a conventional detached unit, and two to four months on a permitted JADU conversion. Orange County city plan check times vary, with Santa Ana and Orange often moving faster than some coastal jurisdictions. A prefab unit from Abodu, Cover, Dvele, or Mighty Buildings can trim the on-site build time by several weeks, and we’ll give you a written schedule with your written price. Call (424) 577-4306 for a timeline on your specific lot.
A detached ADU in Orange County generally runs $220,000 to $460,000 before permit and impact fees, a JADU or garage conversion runs $80,000 to $180,000, and a prefab unit lands between $120,000 and $300,000 before site work. The final number depends on lot access, soil conditions, panel capacity, and city overlay requirements. We put the full price in writing after a free on-site walk-through, so you know your number before you approve anything.
We handle site work and inspections for Abodu, Cover, Dvele, and Mighty Buildings units across Orange County, including foundation, utility hookups, and final city sign-off. If your prefab unit arrived or is arriving, we’ll match the site to the factory specs and pass the inspections. Even if you have another make or a custom conventional build, we can help, and the written price covers what we do from the ground up.
We answer the phone around the clock with a live person, so you can report a failed water line, a broken window from a storm, or an electrical issue in your ADU at noon or midnight. If the defect falls within the one-year written guarantee, we return at no charge and correct it. Call (424) 577-4306 and tell us what’s failing, and we’ll get a crew scheduled.
Every ADU we build is backed for a full year by the written Done Right Promise: if the work fails due to a workmanship defect inside 365 days, we come back and make it right at no charge. The guarantee is spelled out on paper, including what it covers and exactly how we correct it. That’s been The Garrison Standard since 2006, and it’s why homeowners who’ve been burned once don’t get burned twice.
Start by calling us for a free walk-through, because the lot check tells you what actually needs to change: access, drainage, panel capacity, and sewer depth. Don’t clear trees or pour anything before the city approves the plans, because unpermitted site work can complicate the permit. We’ll walk your lot in Orange County and tell you exactly what to do, in the order it needs doing, before you spend a dollar.
Schedule Your ADU Builders Service in Orange County Today
Call (424) 577-4306 and tell us about your lot, your goal, and what’s gone wrong with previous contractors. You’ll get a live person, a free on-site walk-through, and a written price before any work starts. If you’ve been burned before, that’s exactly what you need.
Written by Reed Calloway, Owner at Fielding ADU Orange County, serving Orange County since 2006.
