ADU Builders in Irvine — Plans, Permits & Build, One Fixed Price

Fast, Reliable ADU Builders Across Irvine

ADU construction in Irvine typically costs $180,000 – $420,000 for a detached unit and $120,000 – $240,000 for a garage conversion or JADU, with the HOA architectural review being the make-or-break step most homeowners don’t see coming. We’re Cottage ADU Builders, and we work in Irvine’s master-planned villages every month, from Woodbridge to Great Park. Our ADU Builders team knows which HOA boards move fast, which builders left slab and joist surprises in the original tract homes, and when a standard ADU plan from the City actually saves you time. Call (866) 808-7312 for a free estimate on your project.

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Why Cottage ADU Builders Is Irvine’s Preferred ADU Builders Company

Irvine homeowners don’t hire a general contractor who dabbles in ADUs. They hire someone who has already sat through the architectural review meetings at Turtle Rock, Northwood, and Woodbridge, and who knows that a roofline the City would approve in a day can stall in HOA design review for six weeks. We build ADUs here. That’s the job, not a side line.

We also remodel the kitchens and bathrooms inside the main house, which matters more in Irvine than almost any other Southern California city. A second unit in a 1970s Woodbridge home often comes with a main-house kitchen that’s still on its original builder-grade cabinets. One contractor, one permit sequence, one point of contact. Neil Stratton leads our Irvine work, and he’s built his reputation on showing up to HOA pre-submittal meetings prepared, with drawings that respect the original tract rooflines instead of fighting them.

We stock materials and coordinate with local suppliers along the I-5 and 405 corridors, so our crews aren’t waiting on a parts run from Los Angeles every time a plan check comment lands. That’s the kind of local fluency you only get from doing this work in Irvine repeatedly.

Detached ADU in Irvine

A Detached ADU in Irvine is a standalone unit built in your rear yard, and it’s the most expensive path at $220,000 – $420,000 depending on size, site prep, and finishes. In Irvine specifically, a detached ADU is also the most politically complicated build on your property, because every HOA in this city enforces uniform rooflines, setbacks, and architectural character across entire villages. The City of Irvine runs a standard ADU plan program that streamlines plan check for qualifying designs, but the City’s approval only gets you so far. The HOA architectural review is the real gate.

We tell every Irvine homeowner the same thing before drawings start: submit your concept to the HOA board before you pay for full construction drawings. The HOA won’t reject the idea of an ADU, but they will reject a second-story unit that breaks the street’s roofline rhythm or a footprint that pushes too close to a shared wall. Better to know that in week two than month five.

Working Within Irvine’s Architectural Rules

Turtle Rock and Northwood have some of the strictest standards in the city. A detached ADU with a flat roof will clear the City but may sit in HOA design review indefinitely if every other home on the street has a pitched tile roof. We design detached units that match the parent home’s roofline, eaves, and exterior materials, using James Hardie fiber-cement siding where the original tract home used stucco or wood. Hardie reads as original from the street, which is exactly what the HOA wants to see.

Site Prep for Irvine’s Small Rear Yards

Irvine tract lots from the 1960s through the 1990s are not generous. Many rear yards in Woodbridge and Northwood are 20 feet deep or less. A detached ADU on a slab or crawlspace foundation has to fit within the existing hardscape without killing the main home’s outdoor living area. We do more pier-and-beam and slab-on-grade ADUs in Irvine than anywhere else we work, because the lots simply don’t leave room for a full basement or a wide crawlspace excavation.

JADU in Irvine

A JADU in Irvine, or Junior Accessory Dwelling Unit, is a conversion of existing space inside the home, usually a garage or a large bedroom, into a self-contained living unit under 500 square feet. In Irvine, JADUs run $120,000 – $200,000, and this is the path of least resistance for most homeowners because it doesn’t add a new footprint, doesn’t change the roofline, and usually clears HOA architectural review far faster than a detached build.

Irvine’s warm, dry climate makes the garage the hottest zone on any property. A garage conversion here isn’t just drywall and a door. We upgrade the slab, sister the ceiling joists for habitable load, and add a high-efficiency mini-split because an uninsulated Irvine garage hits 100 degrees in the summer. The City’s standard ADU plan program still applies to JADUs in most cases, but the HOA is typically more relaxed because nothing about the exterior changes except maybe a door and a window.

Garage Slabs and Joists in 1960s – 80s Tract Homes

Original Irvine tract garages from the 1960s through the 1980s were built to hold cars, not people. The slab is often only 3.5 inches thick with no vapor barrier, and the ceiling joists are undersized for a habitable ceiling assembly. Before we frame a single wall, we test the slab and check the joist spans. In Woodbridge, we took a 1970s attached garage with a builder-grade bare slab and undersized ceiling joists and converted it to a JADU, sistering the joists for habitable load, adding an insulated ceiling assembly and a high-efficiency mini-split because that garage was the hottest zone on the property. We kept the existing roofline untouched so the HOA architectural submission moved alongside, not behind, plan check, and finished with a James Hardie-clad entry so the conversion still read as the original tract house from the street.

Junior ADU Kitchens and Bathrooms

Irvine’s HOA rules don’t stop at the front door. A JADU needs a kitchen and a bathroom to be legal as a separate unit, and we handle both trades in-house. That’s the single biggest advantage of working with one contractor who does ADUs and interior remodeling. Your JADU kitchen and bath get built under the same permit, the same schedule, and the same punch-list, instead of you coordinating a separate kitchen remodeler while a framing crew waits on rough-in.

Trusted Brands We Service in Irvine

We work with the brands you’ve already been researching. For Irvine’s compact lots and strict HOA aesthetic rules, Mighty Buildings and Plant Prefab are the two names that come up most often. Mighty Buildings’ panelized units go up fast and can be clad to match a tract home’s exterior, which helps at architectural review. Plant Prefab offers more design flexibility for larger detached units on bigger Great Park lots. We also service Boxabl units for homeowners who want a compact, factory-built studio ADU with minimal site work. We don’t push one brand. Your lot, your budget, the right system. We handle the site prep, foundation, utility hookups, and interior finishes regardless of which manufacturer you choose.

Common ADU Builders Problems We See in Irvine Homes

• Submitting to the City before the HOA. The City of Irvine’s standard ADU plan program is efficient, but an HOA architectural review board in Turtle Rock or Northwood can hold up a detached or two-story ADU for months over roofline and setback uniformity. We reverse the order: HOA concept review first, then full drawings.
• Assuming a 1960s – 80s garage slab is ready. Original Irvine tract garage slabs often lack a vapor barrier and aren’t thick enough for habitable use. We saw this in a Northwood conversion where the slab had to be replaced entirely before framing could start.
• Voiding a builder warranty on a newer Great Park home. Cutting into a builder-grade slab, modifying HVAC chases, or reframing structural walls without documenting the scope can void parts of your home’s original warranty. We sequence the work to preserve coverage and document every structural change.
• Ignoring Irvine’s cooling loads. An attached or garage-conversion ADU needs serious insulation and a properly sized mini-split. The garage is often the hottest zone on the property, and a unit that’s comfortable in March can be unlivable in August without the right mechanical design.

Pricing for ADU Builders in Irvine, CA

We Also Serve Cities Near Irvine

Our ADU Builders in Irvine team works throughout central Orange County. We regularly take on projects in Tustin, Aliso Viejo, Santa Ana, and North Tustin, where HOA rules are less intense but the housing stock is similar. If you’re just outside Irvine, the same crew, the same pricing, and the same permit sequencing apply.

FAQs About ADU Builders in Irvine