Trusted Junior ADU & Interior Conversion for Irvine Homeowners
A Junior ADU & Interior Conversion in Irvine typically runs $85,000-$175,000 all-in, from measured drawings through final inspection, depending on whether you’re converting existing square footage or building an attached addition. Ellery ADU Studio has designed, permitted, and built 900+ ADUs since 2015, the year California’s ADU laws began their major shift, and every project has started with a written price before any work began. We’re a design-build studio, not a contractor, which means the drawings, the permit set, and the construction live under one contract at one fixed price - no designer-versus-builder blame gap when something doesn’t match.
Irvine’s specific landscape matters here. The city’s strict fire separation requirements between primary dwellings and converted spaces, its hillside grading overlays in Turtle Rock and Shady Canyon, and its utility capacity constraints in older villages like Woodbridge mean a junior ADU project can stall for months if the permit set isn’t built for Irvine’s actual conditions from day one. We’ve navigated these exact requirements repeatedly. Our permit sets are reviewed by Irvine’s Planning Division as complete submissions, not iterative guesses. If you already have a written estimate in hand, we’ll provide a Free Second Opinion. Call (657) 233-9738 to schedule yours.
What Our Junior ADU & Interior Conversion Service Includes
Basement ADU
A basement ADU converts below-grade space into a permitted dwelling unit with its own kitchen, bathroom, sleeping area, and separate entrance. In Irvine, this makes particular sense for homes in Northwood and Northpark, where 1970s and 1980s construction often includes full-height basements that were finished informally and never permitted as living space. We measure the existing headroom, egress window feasibility, and moisture conditions; then we produce a permit set that addresses Irvine’s specific requirements for basement ventilation and emergency egress, not generic California code. Our crews are background-checked and uniformed, and every visit produces a documented photo record you receive directly.
Above-Garage ADU
An above-garage ADU, sometimes called a carriage house conversion, builds living space on top of an existing garage structure. This is common in Irvine’s older villages like University Park and El Camino Real, where two-car garages with adequate structural capacity sit underutilized. We start with a structural assessment - the existing slab and framing must handle the added load, and Irvine requires engineered calculations for any modification to the garage’s fire separation from the main dwelling. Our permit set includes those calculations, the fire-rated assembly details, and the utility routing from main to ADU. Because we’re design-build, if the structure needs reinforcement, that scope is in your original written price, not a surprise change order later.
Room-to-ADU Conversion
A room-to-ADU conversion takes existing interior space - a large bonus room, an in-law suite that was never fully permitted, or a ground-floor bedroom wing - and brings it up to full ADU code. In Irvine’s newer villages like Portola Springs and Orchard Hills, homeowners often bought with this flexibility in mind but found the permitting path opaque. We handle the fire separation between units, the separate utility metering or sub-metering that Irvine requires, and the independent exterior access. The Haven Standard, Clause 1, governs: your written price covers drawings through final inspection, with no door-side upsells.
Attached Addition ADU
An attached addition ADU extends the primary dwelling with new construction that functions as a separate unit. This differs from a room conversion because it involves new foundation, framing, and roof tied to the existing structure. In Irvine, setback variances - the extra distance the city requires between your new ADU and the property line - often drive the design more than square footage goals. We’ve worked with Irvine’s setback requirements in compact lots near the Spectrum and in the larger parcels of Turtle Ridge. Our permit set includes the site plan, the floor plan, the elevation drawings, and the structural details as one coordinated package, so the builder can’t claim the designer missed a bearing wall.
Interior JADU
An interior JADU, or Junior Accessory Dwelling Unit, is the most constrained form: maximum 500 square feet, contained entirely within the existing primary dwelling, with no exterior expansion. The owner must reside in either the main unit or the JADU. In Irvine, this appeals to homeowners in condo conversions and townhome communities where exterior construction is restricted by HOA covenants - we’ve worked within these constraints in Woodbridge, Westpark, and the condo villages near John Wayne Airport. Our Junior ADU & Interior Conversion in Tustin neighbors face similar requirements: the JADU requires a kitchenette (not a full kitchen), a separate entrance, and its own bathroom or shared bathroom with specific privacy provisions. Our permit set addresses each of these precisely, because Irvine’s inspectors check them precisely.
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.
Brands We Service for Junior ADU & Interior Conversion
We specify and coordinate prefab and modular systems from Abodu, Cover, and Dvele within the same single-contract design-build model that governs our conventional construction projects. With Abodu, we’ve integrated their One and Two models into attached addition ADUs where the module forms the core living space and our crew builds the connecting structure and utility tie-ins to Irvine code. Cover’s panelized system works well for above-garage ADUs in Northwood, where crane access is tight and the precision of factory-cut panels reduces field modifications. Dvele’s fully finished modules require exact foundation prep; our permit set includes the module-specific structural connection details that Dvele demands and Irvine’s building department reviews.
Whether your project involves James Hardie siding on a conventional stick-frame conversion, a modular system from one of these brands, or any other make or material package, we can specify, coordinate, and warrant the result under one written contract. The 365-Day Done Right Promise applies regardless of construction method: if the finished ADU is not built to the permitted drawings, we make it right, in writing, before your project starts.
Signs You Need Junior ADU & Interior Conversion Right Now
- Your adult child has moved back home and needs independent space. The “boomerang” phenomenon is common in Irvine, where housing costs push young professionals back to the family home. A JADU or basement conversion preserves family relationships while creating legal, rentable square footage that adds to your property’s long-term value.
- You’re paying a mortgage on square footage you don’t use. Finished basements, bonus rooms, and oversized garages in Irvine’s older villages represent dormant equity. Every month that space sits unpermitted and unrented is a month you’re not offsetting your housing cost with legal rental income.
- Your in-law suite was built without permits and you’re worried about code enforcement. Unpermitted living space is a liability in Irvine, where code compliance complaints can trigger inspections and required abatement. A permitted conversion protects your investment and often increases your coverage with your insurer.
- Your HOA prohibits detached structures but allows interior modifications. Many Irvine villages have covenants that block backyard cottages but say nothing about interior JADUs or basement conversions. We review your CC&Rs as part of our initial assessment and design within actual constraints, not assumptions.
- You’re approaching retirement and want rental income without landlord complexity. A JADU with a long-term tenant in your own home is simpler than managing a separate property, and Irvine’s stable rental market supports this strategy. The conversion cost is typically recoverable within 5-7 years of rental income.
Our Junior ADU & Interior Conversion Process - Step by Step
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Site assessment and feasibility study. We visit your Irvine property, measure existing conditions, photograph everything, and record utility locations. You receive this documented photo record within 24 hours. We identify structural constraints, setback requirements, and any hillside or flood zone overlays that affect your specific lot. This assessment is free and comes with no obligation.
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Written price and scope under Haven Standard Clause 1. Within one week of assessment, you receive a single written price covering design, permit set, construction, and final inspection. The scope is itemized by trade: demolition, framing, MEP (mechanical, electrical, plumbing), finishes, and utility connections. Under Clause 5 (No Surprises), this scope locks at signing.
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Permit set production and submission. Our designers produce architectural drawings, structural calculations, Title 24 energy compliance, and Irvine-specific fire separation details. We submit to Irvine’s Planning Division and Building Division as a complete package, not a phased submission that invites delay. We track the permit through plan check and respond to corrections directly.
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Construction with documented progress. Our background-checked, uniformed crews execute the work to the permitted drawings. Every site visit generates a documented photo record you receive showing what was found, what was done, and what comes next. The license number appears on every page of our documentation and on every crew vehicle.
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Final inspection and 365-Day Done Right Promise activation. We walk every inspection with Irvine’s building inspector, address any corrections immediately, and deliver your final permit and certificate of occupancy. The 365-Day Done Right Promise then governs: if anything is not built to the permitted drawings, we return and make it right at our expense.
How Much Does Junior ADU & Interior Conversion Cost in Irvine?
A typical interior JADU in Irvine runs $85,000-$125,000 all-in, drawings through final inspection - see how much Junior ADU & Interior Conversion costs across project types. A basement ADU or room-to-ADU conversion typically falls between $110,000 and $155,000, depending on whether the existing space needs structural modification, moisture remediation, or new utility routing. An above-garage ADU usually ranges $130,000-$175,000, with the higher end reflecting structural reinforcement of the existing garage and the fire-rated stair or exterior access structure. An attached addition ADU, involving new foundation and roof work, generally starts around $150,000 and can reach $220,000 for larger footprints or complex hillside conditions in Turtle Rock or Shady Canyon.
Several factors move these ranges. Existing structural capacity is the largest variable: a garage slab that can bear the load without reinforcement saves $15,000-$25,000 compared to one that needs underpinning or replacement. Utility distance matters too - extending sewer, water, and electrical from a main dwelling at the front of a deep lot to an attached addition at the rear adds trenching and material cost. Irvine’s specific fire separation requirements between units, more stringent than many California cities, add assembly cost that generic estimates often miss. Finish level moves the needle less than homeowners expect; the structural, mechanical, and permit infrastructure is the bulk of the investment.
To avoid overpaying, get a written line-item quote that separates design and permit costs from construction, so you can compare apples-to-apples. Beware estimates that assume your existing structure is adequate without inspection. Ask specifically whether the price includes Irvine’s plan check fees, school district fees, and utility connection fees, which together can reach $8,000-$12,000 and are sometimes omitted from initial quotes. Our written prices include all known fees; if the city adds a new fee category after signing, Haven Standard Clause 5 governs how we handle it.
Every free estimate we provide includes the site assessment, the documented photo record, the written price with line-item breakdown, and a copy of The Haven Standard for your review. Call (657) 233-9738 to schedule yours.
Junior ADU & Interior Conversion Near Irvine - Our Service Area
We serve homeowners throughout Orange County from our Irvine base, with typical project timelines that reflect each city’s permit processing speed. Junior ADU & Interior Conversion in Tustin moves on a similar schedule to Irvine, often 4-6 months from permit submission to final inspection. Junior ADU & Interior Conversion in Lake Forest can extend slightly longer due to Orange County Fire Authority review for hillside properties. We also work regularly in Santa Ana, Mission Viejo, Costa Mesa, Newport Beach, Orange, Laguna Beach, Anaheim, Garden Grove, and Huntington Beach. Travel to your property is included in your written price; no mileage add-ons or zone surcharges appear in our contracts. If you’re unsure whether your specific address falls within our service area, call (657) 233-9738 and we’ll confirm directly.
Serving Irvine, CA - Our Local Coverage Area
We’re based in the Irvine 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 - Junior ADU & Interior Conversion in Irvine
A Junior ADU is a specific type of small dwelling unit, maximum 500 square feet, created within the existing walls of a single-family home, with the owner residing in either the main unit or the JADU. Interior conversion is the broader category that includes JADUs plus basement ADUs, above-garage ADUs, room-to-ADU conversions, and attached additions, all of which repurpose existing space or add connected new space rather than building a detached structure. Ellery ADU Studio handles all five sub-types - including our Junior ADU & Interior Conversion in Santa Ana - under one contract at one written price. Call (657) 233-9738 for an exact quote on your specific space - estimates are free.
From signed contract to certificate of occupancy, most projects take 8-14 months, with 3-5 months for permit set production and city review, and 5-9 months for construction depending on complexity. Irvine’s Planning Division typically takes 6-10 weeks for initial plan check, with one correction cycle common. Basement ADUs with moisture remediation or above-garage ADUs requiring structural reinforcement trend toward the longer end. We provide a written timeline with your price, and The Haven Standard includes progress milestones you can verify. Call (657) 233-9738 to discuss your specific timeline.
Interior JADUs typically run $85,000-$125,000, basement and room conversions $110,000-$155,000, above-garage ADUs $130,000-$175,000, and attached additions $150,000-$220,000, all-in from drawings through final inspection. The specific factors are structural condition, utility routing distance, and finish selections, in that order. Every project receives a written price before any work begins, per Haven Standard Clause 1. Call (657) 233-9738 for your exact quote - estimates are free.
Yes, we specify and coordinate Abodu, Cover, Dvele, and other modular systems within our single-contract model, though prefab integration is more common for attached additions and above-garage ADUs than for pure interior conversions where factory modules don’t fit. For a basement JADU, conventional stick-frame construction with James Hardie exterior finishes is typically more practical. We recommend the right construction method for your specific project, not the method that simplifies our logistics. Call (657) 233-9738 to discuss whether prefab makes sense for your space.
Junior ADU and interior conversion work is planned construction, not emergency repair, so we do not promise same-day or emergency dispatch for this service category. A live person answers our phones 24/7 to schedule your free estimate, discuss your project timeline, or coordinate if an active construction issue arises. For genuine emergencies involving structural compromise or utility hazard on an active job site, our project manager responds directly. Call (657) 233-9738 to start the planning process.
The 365-Day Done Right Promise governs every project: if the finished ADU is not built to the permitted drawings, we make it right at our expense within one year of final inspection. This is backed in writing before your project starts, not a verbal assurance. Beyond this, standard manufacturer warranties apply to specific materials and fixtures, and our workmanship carries the statutory warranty period for construction defects. We provide all warranty documentation at project closeout. Call (657) 233-9738 for the full Haven Standard terms.
Gather any existing plans, surveys, or previous permits for your property, and note any HOA covenants or neighborhood restrictions you’re aware of. If you have a written estimate from another firm, bring it for our Free Second Opinion. We’ll handle the measurement, photography, and code research from there. No cleaning, clearing, or preparation of the space itself is necessary for our initial assessment. Call (657) 233-9738 to schedule - estimates are free and come with no obligation.
Schedule Your Junior ADU & Interior Conversion Service in Irvine Today
Call (657) 233-9738 to schedule your free estimate. A live person will answer, 24/7, and you’ll receive a written price before any work begins, a documented photo record on every visit, and the 365-Day Done Right Promise in writing. Whether you’re converting a basement in Northwood, building above a garage in University Park, or adding a JADU in Woodbridge, we’ll produce the permit set and execute the construction under one contract at one fixed price. No designer-versus-builder gaps. No call-for-quote runaround. Just the work, named, in order, at the price you were quoted.
Written by Nadia Ellery, Owner at Ellery ADU Studio, serving Irvine since 2015.