Trusted Junior ADU & Interior Conversion for Chino Homeowners
A Junior ADU & Interior Conversion in Chino typically runs $85,000-$165,000 all-in, from measured drawings through final inspection, depending on whether you’re converting existing interior space or adding attached square footage. 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 starts with a written price before any work begins. Call (909) 323-1107 to schedule your free estimate, or bring us any written estimate already in hand for a Free Second Opinion.
Chino’s housing stock - particularly the ranch homes north of the 60 Freeway and the newer developments near The Preserve - presents a specific opportunity. Many of these properties have underutilized basements, attached garages with interior access, or bonus rooms that never quite worked as bedrooms. A Junior ADU, or JADU, is a self-contained living unit created entirely within the walls of an existing single-family home, with its own entrance, cooking facilities, and bathroom. An interior conversion can also produce a full ADU if the space and zoning allow. The distinction matters for your permit path, your utility connection strategy, and your final budget. We’re a design-build studio, not a contractor who outsources drawings, which means the person who measures your space also seals the permit set and manages the build. No designer-versus-builder blame gap when something doesn’t line up.
Chino’s climate is relatively mild, but our summer heat and occasional Santa Ana wind events do affect material choices and ventilation design. We specify accordingly. Our license number appears on every page we publish, and our crews are background-checked and uniformed. Under The Haven Standard, Clause 1, you receive a written price before any work starts. Clause 5 locks the scope at signing. Our 365-Day Done Right Promise is backed in writing before your project begins.
What Our Junior ADU & Interior Conversion Service Includes
Basement ADU
A Basement ADU converts below-grade space into a permitted, rentable unit with egress windows, dedicated HVAC, and separate metering where the city allows. In Chino, we most often see this opportunity in 1970s-1990s homes near Chino Hills or along Central Avenue, where full basements were included in the original construction but never finished to living standards. Ellery ADU Studio measures existing ceiling height against Chino’s code minimums, designs the egress window wells to avoid water intrusion in our clay-heavy soils, and coordinates the permit set as part of your single contract. We do not hand off to a separate designer or drafter.
Above-Garage ADU
An Above-Garage ADU adds a second story over an existing attached or detached garage, or converts unfinished attic truss space above. This works well on Chino’s narrower lots where setback requirements prevent ground-level expansion, particularly in the College Park area and near Cypress Avenue where lot widths average 50-60 feet. We evaluate the existing foundation and wall framing for load capacity, design the stair access to meet Chino’s fire separation requirements, and specify insulation and soundproofing appropriate for the temperature swings our inland valley sees. The permit set includes structural calcs and Title 24 energy compliance, not just floor plans.
Room-to-ADU Conversion
A Room-to-ADU Conversion takes an existing bedroom, den, or large bonus room and creates a self-contained unit with kitchenette, full bath, and separate entrance. This is often the fastest path to rental income in Chino, especially in newer homes where the original floor plan included a “mother-in-law suite” that was never properly permitted. We assess whether your existing space meets the minimum square footage for a JADU (150 sq ft) or full ADU, design the kitchenette around your available electrical service, and document the fire-rated separation between unit and main house. Our photo record on every visit shows you exactly what we found, not what we felt about it.
Attached Addition ADU
An Attached Addition ADU extends the footprint of your existing home to create new living space that functions as a separate unit. This differs from a room conversion because we’re adding square footage, which triggers Chino’s setback, height, and lot coverage calculations more stringently. We see strong demand for this in The Preserve and newer Chino developments where homeowners want to keep architectural consistency with the original structure. Ellery ADU Studio produces the full permit set, including site plan, floor plan, elevations, and structural details, under the same contract that covers construction. One price, one point of accountability.
Interior JADU
An Interior JADU is the most restrictive but often most affordable category: a unit of no more than 500 square feet, created within the walls of an existing single-family home, with owner-occupancy required in either the JADU or the main residence. In Chino, this frequently means converting a ground-floor bedroom and adjacent bathroom near an existing exterior door. We verify your property’s eligibility against Chino’s local JADU ordinance, which may impose additional requirements beyond state law, and we design to the “efficiency kitchen” standard that JADUs require. The permit set includes the owner-occupancy affidavit and utility connection plan. Under Haven Standard Clause 1, your written price covers drawings through final inspection.
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
Ellery ADU Studio specifies and coordinates prefab and modular systems within our single-contract design-build model. For interior conversions and JADUs, we most frequently integrate Mighty Buildings panelized bathroom and kitchen modules when the project benefits from factory precision and reduced on-site construction time. We’ve specified Mighty Buildings units in 40+ Chino-area projects and coordinate their MEP connections with our permit set, not as an afterthought. Boxabl Casita units see occasional use in attached addition ADUs where the module dimensionally fits the available footprint; we evaluate structural compatibility and crane access as part of our initial site assessment, and we document any foundation modifications required in the permit set.
Plant Prefab systems appear in our higher-end interior conversions where the client wants premium finishes and faster close-in. We’ve coordinated Plant Prefab’s custom panel packages with Chino’s building department on multiple projects, and we understand their lead times and inspection requirements. Whether your project involves Mighty Buildings, Boxabl, Plant Prefab, or conventional stick-frame construction, we can help. Our expertise is in matching the system to your site conditions, your budget, and Chino’s specific code interpretation, then delivering a single written price for the complete scope.
Before
AfterSigns You Need Junior ADU & Interior Conversion Right Now
- You’re carrying a mortgage rate above 5.5% and need rental income to offset it. Chino homeowners who bought between 2015 and 2022 are increasingly looking at ADUs as long-term income assets, not weekend projects. A permitted JADU renting at market rate can offset $1,200-$1,800 monthly of your housing cost. The permitting path is clearer now than it was before 2020, but delays are increasing as application volume rises.
- You have an adult child or aging parent who needs independent living space. Multi-generational households are common in Chino, but unpermitted “in-law quarters” create liability exposure and can’t be legally rented if circumstances change. A permitted JADU or interior ADU gives you flexibility: family use now, rental income later, legal compliance throughout.
- Your property has an unfinished basement, bonus room, or attached garage with interior access. These are the raw materials for conversion, and they’re depreciating assets if unused. In Chino’s climate, unfinished basements are particularly prone to moisture issues that worsen over time. Converting now, with proper waterproofing and ventilation designed in, protects your structure while adding value.
- You’ve received a notice from the City of Chino about unpermitted living space. This is not uncommon when a previous owner created a “studio apartment” without permits. The city can require removal or full permitting, and the permitting path is more expensive if you’re forced into it reactively. Proactive conversion, with a complete permit set and code-compliant design, avoids emergency costs and potential fines.
- Your household income has shifted and you need to monetize your largest asset. Job changes, medical expenses, or retirement timing can make an ADU transition from “someday” to “this year.” The design-build timeline for a JADU conversion in Chino typically runs 6-10 months from contract to certificate of occupancy. Starting the conversation now, with a written price in hand, lets you plan rather than react.
Our Junior ADU & Interior Conversion Process - Step by Step
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Site Assessment & Feasibility Study. We visit your Chino property with laser measure, moisture meter, and structural assessment tools. We document existing conditions with a photo record you receive same-day. We evaluate ceiling heights, egress paths, electrical panel capacity, and HVAC zoning. Within 48 hours, you receive a feasibility memo: what’s possible, what the code requires, and what constraints we’ll design around.
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Schematic Design & Written Price. Based on the feasibility study, we produce schematic floor plans and a line-item written price. Under Haven Standard Clause 1, this price is fixed before any work begins. It includes the permit set, all construction, and our 365-Day Done Right Promise. No “allowances” that balloon later. We also note any items that require your decision, with price implications for each option.
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Permit Set Production & Submission. Our in-house designers produce the complete permit set: site plan, floor plans, elevations, sections, structural calculations, Title 24 energy compliance, and plumbing/electrical plans. We submit to Chino’s Building & Safety Division and manage any corrections or clarifications. You receive a copy of every submittal and every response.
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Construction & Inspection Coordination. Our crews execute the build according to the permitted drawings. A documented photo record accompanies every site visit. We coordinate all inspections, from rough electrical to final occupancy, and we do not request final payment until the certificate of occupancy is issued. If the city requires corrections, we make them at our expense.
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Final Walkthrough & Warranty Activation. We conduct a punch-list walkthrough with you, using the permit set as our reference standard. The 365-Day Done Right Promise activates at certificate of occupancy. If anything is not built to the permitted drawings, we make it right. The warranty, the photo record, and the final permit set are delivered as your permanent project documentation.
How Much Does Junior ADU & Interior Conversion Cost in Chino?
A typical Interior JADU conversion in Chino runs $85,000-$125,000 all-in, from measured drawings through final inspection. A Room-to-ADU Conversion with full kitchen and bath, not limited to the JADU efficiency standard, typically ranges $110,000-$155,000. Basement ADUs, which require egress windows, moisture management, and often dedicated HVAC, generally fall between $125,000-$165,000. Above-Garage ADUs start around $140,000 and can exceed $200,000 if structural reinforcement or foundation work is required. Attached Addition ADUs, because they involve new foundation and roof work, typically range $175,000-$250,000 depending on square footage and finish level.
| Conversion Type | Typical Range in Chino | Primary Cost Drivers |
|---|---|---|
| Interior JADU | $85,000 - $125,000 | Existing bathroom proximity, electrical panel capacity, separate entrance location |
| Room-to-ADU Conversion | $110,000 - $155,000 | Full kitchen vs. efficiency kitchen, HVAC zoning, soundproofing requirements |
| Basement ADU | $125,000 - $165,000 | Egress window wells, moisture barrier, ceiling height modifications |
| Above-Garage ADU | $140,000 - $200,000+ | Structural load capacity, stair access, fire separation |
| Attached Addition ADU | $175,000 - $250,000 | Foundation type, roof tie-in, lot coverage calculations |
What moves the needle within these ranges? Three factors dominate Chino projects. First, existing conditions: a basement with 7’6″ ceiling height needs less work than one at 6’8″. Second, utility capacity: if your electrical panel is full or your sewer lateral is undersized, upgrades add cost but also add value and code compliance. Third, finish specifications: we quote standard finishes in our base price and note upgrades with exact dollar impacts, so you choose consciously.
How to avoid overpaying: get a written, line-item estimate from any provider you’re considering, then bring it to us for a Free Second Opinion. We frequently find padded allowances, omitted permit costs, or unrealistic “builder’s risk” contingencies. Under Haven Standard Clause 5, our scope is locked at signing. No door-side upsells, no scope creep. What’s included in our free estimate: site visit, feasibility memo, schematic design, and written price. Call (909) 323-1107 to schedule.
Junior ADU & Interior Conversion Near Chino - Our Service Area
Ellery ADU Studio serves Chino and the surrounding San Bernardino and western Riverside County corridor. Typical projects cluster in Chino proper, Chino Hills to the south, and Eastvale to the east, with additional work in Ontario, Montclair, Pomona, Diamond Bar, Corona, Upland, Anaheim, Rancho Cucamonga, and Fontana. Response time for initial site assessment is typically 3-5 business days in Chino and adjacent cities. Permit familiarity varies by jurisdiction, and we maintain current knowledge of each city’s ADU ordinance interpretation, not just state minimums. For Chino Hills and Eastvale specifically, see our dedicated service pages for local code nuances.
Serving Chino, CA - Our Local Coverage Area
We’re based in the Chino 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 Chino
A Junior ADU (JADU) is a self-contained living unit of no more than 500 square feet, created entirely within an existing single-family home, with an efficiency kitchen, separate entrance, and either its own bathroom or shared bathroom access. An interior conversion can also produce a full ADU if the space and zoning allow, which removes the 500-square-foot cap and owner-occupancy requirement but requires more extensive code compliance, as we explain for Chino Hills Junior ADU & Interior Conversion projects as well. The distinction affects your permit path, utility strategy, and rental flexibility. Call (909) 323-1107 and we’ll assess which category your Chino property qualifies for.
From contract signing to certificate of occupancy, a typical Interior JADU in Chino takes 6-10 months: 2-3 months for permit set production and city review, 3-5 months for construction, and 2-4 weeks for final inspections. Basement and above-garage conversions often run longer due to structural and MEP complexity. Chino’s Building & Safety Division currently reviews ADU permits in 4-6 weeks for complete submittals, but corrections add time. Our permit set completeness rate is high because we design in-house and know the city’s expectations. Call (909) 323-1107 for a timeline based on your specific project.
Interior JADU conversions in Chino typically run $85,000-$125,000 all-in, while full interior ADU conversions range $110,000-$155,000 depending on kitchen, bath, and HVAC scope, similar to our Junior ADU & Interior Conversion in Corona. Basement, above-garage, and attached addition ADUs carry higher ranges due to structural and egress requirements. Every Ellery ADU Studio project receives a written, line-item price before any work begins, per Haven Standard Clause 1. We do not provide ballpark figures that change later. Call (909) 323-1107 for your specific written estimate, or bring us any competing quote for a Free Second Opinion.
Yes. We specify and coordinate Mighty Buildings, Boxabl, and Plant Prefab systems within our single-contract design-build model, and we’ve integrated these brands in 40+ Chino-area projects. Mighty Buildings modules work well for bathroom and kitchen pods in JADU conversions. Boxabl and Plant Prefab see use in attached additions where dimensional constraints and finish quality justify the approach. We evaluate structural compatibility, crane or forklift access, and Chino’s inspection requirements as part of our initial feasibility study. Call (909) 323-1107 to discuss whether a modular approach fits your project.
We do not treat ADU conversion as an emergency dispatch service, but we do prioritize clients who have received city notices with compliance deadlines. If Chino Building & Safety has flagged unpermitted living space, reactive permitting is typically more expensive and slower than proactive conversion. We can assess your situation within 3-5 business days and produce an expedited feasibility memo. The written price and permit set follow our standard process, but we coordinate with the city to meet your compliance timeline. Call (909) 323-1107 to discuss urgency and next steps.
Every project is covered by our 365-Day Done Right Promise: if the finished ADU is not built to the permitted drawings, we make it right, backed in writing before construction starts. This is Haven Standard warranty language, not a vague satisfaction claim. It covers workmanship, material installation, and code compliance. Beyond one year, manufacturer’s warranties on fixtures, appliances, and major systems apply as specified. We deliver your complete permit set, photo record, and warranty documentation at project closeout. Call (909) 323-1107 to review the exact warranty terms for your project type.
Gather any existing property surveys, previous permits, or architectural plans you have. Note the locations of your electrical panel, main water shutoff, and HVAC equipment. Be prepared to discuss your intended use: rental income, family housing, or future flexibility. If you have a written estimate from another provider, bring it for our Free Second Opinion. We’ll handle the technical assessment: ceiling heights, egress paths, structural loads, and utility capacity. The site visit takes 60-90 minutes, and you’ll receive your photo record and feasibility memo within 48 hours. Call (909) 323-1107 to schedule.
Schedule Your Junior ADU & Interior Conversion Service in Chino Today
Call (909) 323-1107 to schedule your free estimate. A live person answers 24/7, no voicemail queue. You’ll receive a written, line-item price before any work begins, per Haven Standard Clause 1. Bring any existing estimate for a Free Second Opinion. Ellery ADU Studio has operated as a design-build studio since 2015, with 900+ ADUs designed, permitted, and built across Chino and the surrounding cities. Your project gets one contract, one point of accountability, and a 365-Day Done Right Promise backed in writing.
Written by Nadia Ellery, Owner at Ellery ADU Studio, serving Chino since 2015.