Fast, Reliable New Detached ADU Across Santa Ana
A new detached ADU in Santa Ana typically costs $280,000 to $420,000 all-in, from drawings and permits through final inspection. That range accounts for what we actually find on Santa Ana lots: 1940s-1960s bungalows with 60-amp panels, galvanized plumbing, and detached garages poured on slabs that were never meant to hold a dwelling. The number moves based on whether you’re building from the ground up or converting an existing structure, and we lock that number in writing before any work starts. Call (971) 497-2402 to schedule a free estimate and get the exact written price for your property.
We know Santa Ana’s streets because we work them every week: the bungalow rows off Bristol, the deeper lots near Santiago Park, the original tracts around Floral Park and West Floral Park. Santa Ana is one of the densest cities in the country, and that density changes what an ADU project looks like here compared to Tustin or Costa Mesa. Your lot is likely already at or near its coverage limit. Your rear garage may be the only realistic place to add square footage. And that garage, if it’s original, probably has problems you won’t see until the walls come down. That’s where our New Detached ADU process starts: with the inspection that tells you what the permit will actually require.
Why Ellery ADU Studio Is Santa Ana’s Preferred New Detached ADU Company
Nadia Ellery founded this studio in 2015, the year California’s ADU permitting rules shifted. Since then we’ve designed, permitted, and built over 900 ADUs, every one of them under a single contract with a written price before work began. That matters in Santa Ana because the homes here are old enough to hide things, and most ADU projects run into at least one of those hidden things. Our contract anticipates that. The Haven Standard, which governs every project, puts the scope in writing and locks it at signing. When we open a wall and find cloth-wrapped wiring, that’s not a surprise to us. It’s a line item we’ve already allowed for.
We coordinate scheduling and permitting from our Los Angeles office, and our crews serve Santa Ana locally. Our license number appears on every page of this site and on every document we hand you. The people who show up at your house are background-checked and uniformed. And a live person answers our phone 24/7, no voicemail queue, because when you’re six figures into a project, you should be able to reach a human who knows your address.
Santa Ana requires patience and paperwork. We handle both. Setback variances, lot coverage ratios, electrical service upgrades triggered by the second unit – none of it is new to us here. The question we hear most from Santa Ana homeowners is whether their garage can even support an ADU. Sometimes the answer is yes. Sometimes it’s no, and the honest answer saves you from a permit revision two months in.
Our New Detached ADU Services in Santa Ana
Every detached ADU in Santa Ana falls into one of these approaches. We’ll tell you which fits your lot, your garage, and your budget, and we’ll write the number down before you commit.
Custom Built ADU
A ground-up detached ADU on a Santa Ana lot means working around what’s already there: mature trees with root zones you can’t disturb, setbacks that squeeze buildable area to a narrow strip along the rear property line, and a house that was built before modern building codes existed. We handle the design, the permit set, and the construction as one contract. For a custom build, plan on $320,000 to $450,000 in Santa Ana, depending on finishes and site conditions. The drawings come first, the price comes with the drawings, and the build follows the drawings exactly.
Studio ADU
A studio ADU is the straightforward option: one open living space, a bathroom, a kitchenette. In Santa Ana, studios usually pencil out around $210,000 to $280,000 as a garage conversion, or $290,000 to $360,000 as new construction. But the studio is also where we see the most permit trouble from homeowners who assumed a garage conversion was cosmetic. We’ll tell you what the city requires before you sign anything.
1-Bed & 2-Bed ADU
Santa Ana’s large multigenerational households drive most of our 1-bed and 2-bed ADU work here. We’re building for aging parents, adult children, and extended family far more often than for rental income. A 1-bed detached ADU in Santa Ana runs $260,000 to $380,000. A 2-bed runs $310,000 to $430,000. The size difference is modest; the cost difference comes from the second bedroom’s egress, closet, and the extra bathroom fixture count that changes your permit classification. We’ll show you the line items.
Prefab ADU Installation
Santa Ana’s older neighborhoods have narrow driveways and tight side yards, which complicates modular delivery but doesn’t rule it out. We coordinate prefab and modular systems from Abodu, Cover, and Dvele within the same single contract. A prefab ADU in Santa Ana runs $240,000 to $380,000 installed, including the foundation, site work, and utility connections. The factory builds the unit; we build everything it sits on and everything that connects it to your house, your panel, and your sewer line.
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 Santa Ana
When a Santa Ana project calls for a prefab or modular system, we specify and coordinate it. We work regularly with Abodu, Cover, and Dvele, and we know how their units interact with Santa Ana’s permit process, soil conditions, and existing utility runs. A Dvele unit has different foundation requirements than an Abodu unit. A Cover unit ships in panels and assembles on site, which matters when your rear lot access is a 38-inch passage between the house and the fence. We handle the coordination, the subs, and the single written price, so you’re not chasing three companies and a factory rep. That’s the entire point of the one-contract model.
Common New Detached ADU Problems We See in Santa Ana Homes
- The 3-inch slab with no footings. Contractors working Santa Ana’s older westside neighborhoods commonly find that detached garages slated for ADU conversion were poured on minimal 3-inch slabs with no perimeter footings, a 1950s shortcut to save concrete. The slab must be broken out and a code-compliant foundation poured before framing can begin. If your budget assumed the slab was fine, this is the line item that moves it.
- The original 60-amp panel. Santa Ana bungalows from the 1940s through the 1960s routinely carry 60-amp electrical panels. The moment you add a second dwelling unit, the city requires a service upgrade, and that’s before your new ADU subpanel gets fed. We write the panel upgrade into the contract from day one, so it never shows up as a door-side surprise.
- Cooling loads nobody calculated. Santa Ana sits inland from the marine layer that keeps coastal Orange County mild. Summer afternoons here reach the mid-90s regularly. A garage conversion with a window unit will not hold temperature, and it will fail HERS verification. We run the load calculation and spec real mechanical cooling, because a wall-shaker in a Santa Ana August is not a livable dwelling.
- Galvanized supply plumbing. Original galvanized pipes in a 1950s Santa Ana house are at the end of their service life. Opening walls for an ADU conversion triggers a repipe more often than homeowners expect, and the city will not pass a new dwelling on failed supply lines. We inspect first, write the allowance into the contract, and show you photos of what we found.
Pricing for New Detached ADU in Santa Ana, CA
Here are honest ranges for Santa Ana, as of 2026. A garage conversion ADU runs $180,000 to $300,000 when the existing structure is sound; add $15,000 to $40,000 if the slab needs to be broken out and repoured with footings. A new detached ADU runs $280,000 to $450,000, with custom builds at the top of that range. The electrical service upgrade from 60 to 200 amps runs $4,500 to $9,000 depending on your panel location and the utility’s requirements. A full repipe of the existing house, when the ADU triggers it, runs $8,000 to $16,000. Under Clause 1 of The Haven Standard, every one of these numbers gets written down before work starts, and under Clause 5, the scope doesn’t move unless you approve a priced change order in writing. Call (971) 497-2402 for a free estimate. We’ll inspect the garage, the panel, and the slab, and you’ll have a written number.
We Also Serve Cities Near Santa Ana
Our crews work throughout Santa Ana and the surrounding Orange County cities. We serve Tustin’s older tracts, the bungalow neighborhoods of Orange, Garden Grove’s dense residential westside, and Costa Mesa’s east side. The permitting jurisdictions change; the process doesn’t. One contract, one written price, one team accountable for the result. If you’re in a neighboring city and weighing a detached ADU, the same standards apply.
Serving Santa Ana, CA - Our Local Coverage Area
We’re based in the Santa Ana 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 - New Detached ADU in Santa Ana
Yes, in most cases. Detached garages built in Santa Ana’s 1940s-1960s tracts were frequently poured on 3-inch slabs with no perimeter footings, which does not meet current code for a dwelling. You’ll need the slab broken out and a proper foundation poured before framing. We verify slab thickness and footing presence during our first inspection and write the foundation line item into your contract before you sign. Call (971) 497-2402 for an exact assessment.
Because Santa Ana’s older housing stock carries 60-amp panels, and the city requires adequate service capacity before it will sign off on a second dwelling unit. Adding an ADU subpanel to an already-maxed 60-amp service creates overload conditions. The permit triggers the upgrade. We include the service upgrade in your written price from the start, so it’s not a discovery item later. Call (971) 497-2402 and we’ll look at your panel during the free estimate.
We stop and show it to you. On a 1952 bungalow in West Floral Park, our crew opened the rear garage walls and found original cloth-wrapped wiring feeding from a 60-amp panel. We pulled the permit, upgraded to 200 amps, and wrote the foundation allowance into the contract before construction started. When we found the 3-inch slab with no footings, the change order was already priced and approved before we brought in the concrete saw. That’s how the process is supposed to work: inspection first, allowances in the contract, price approved in writing before we touch anything. Call (971) 497-2402 to schedule your inspection.
Sometimes. Santa Ana lots are typically 5,000 to 6,500 square feet with bungalows that already consume most of the allowed lot coverage. Many homeowners find that a new detached structure simply won’t fit within the city’s setback and coverage rules, which is why garage conversions and JADUs are the dominant ADU types here. We’ll pull your lot data, check the coverage ratio, and tell you honestly whether new construction is possible or whether a conversion is your realistic path. Call (971) 497-2402 for a free estimate and a straight answer.
Because Santa Ana sits inland from the coastal marine layer, so summer temperatures regularly hit the mid-90s. A window unit can’t hold a dwelling at a livable temperature during Santa Ana’s hot afternoons, and it will fail HERS verification, which the city requires for a permitted ADU. We run the cooling load calculation during design and spec a properly sized mechanical system, not a wall-shaker. Call (971) 497-2402 and we’ll explain the requirements for your specific project.
Written by Nadia Ellery, Owner at Ellery ADU Studio, serving Santa Ana since 2015.