Trusted New Detached ADU for Rialto Homeowners
A New Detached ADU - Rialto typically costs $220,000-$420,000 all-in, from the first site survey through final inspection, depending on size, finish level, and whether you build custom or go prefab. Ellery ADU Studio has designed, permitted, and built over 900 ADUs since 2015, the year California’s ADU laws began their major shift. Every project starts with a written price before any work begins, backed by Haven Standard Clause 1. If you’re adding rental income, housing family, or building a home office on your Rialto property, a detached ADU is usually the highest-ROI option. Call (951) 476-1467 to schedule your free estimate.
We’re a design-build studio, not a designer who hands off to a contractor. That means the drawings, the permit set, and the construction live under one contract at one written price. When the framing doesn’t match the plans, there’s no one to blame. We fix it. That’s the 365-Day Done Right Promise, and it’s in writing before your project starts. Rialto’s specific zoning, the home lot sizes in neighborhoods like Bloomington and the older tracts south of the 10, and San Bernardino County’s fire clearance requirements all factor into how we size and site your ADU.
What Our New Detached ADU Service Includes
Custom Built ADU
A custom built ADU is designed from your property’s specific dimensions, your budget, and how you plan to use the space. You need this when your lot has irregular setbacks, significant slope, or you want finishes and a layout that don’t come off a standard menu. At Ellery ADU Studio Rialto, we start with a measured site survey, produce a full permit set including Title 24 energy calculations, and build from that set. The price is fixed at signing under Haven Standard Clause 1, so the cost of your custom cabinets or the upgraded HVAC doesn’t shift once framing starts.
Prefab ADU Installation
Prefab ADU installation means the unit is manufactured off-site, delivered in modules or panels, and set on your foundation. You need this when speed matters, when you want factory-controlled quality, or when your Rialto lot is tight and a long construction schedule would disrupt parking or access. We specify and coordinate prefab systems from brands including Abodu, Plant Prefab, and Tuff Shed within the same single contract. The permit set still comes from us, the foundation and utility tie-ins are still built by our crews, and the written price covers the entire scope.
Modular ADU
A modular ADU is built to the California Building Code in a factory, transported in one or more modules, and craned onto your prepared foundation. You need this when you want the fastest path from permit to occupancy, or when you’re building a 2-bedroom unit that would take eight months stick-built but can be delivered in twelve weeks. We coordinate with modular manufacturers including Dvele and Mighty Buildings, but the contract is with Ellery. We handle the Rialto building department submittals, the utility coordination with Rialto Water Services and Southern California Edison, and the set and finish work on site.
Studio ADU
A studio ADU is a single-room detached unit with a full bathroom and kitchenette, typically 300-450 square feet. You need this when your Rialto lot is limited by setback or lot coverage rules, when the ADU is for one person, or when you want the lowest all-in cost for rental income. We design studio ADUs to maximize usable space, not just square footage. In Rialto’s warmer climate, that means strategic window placement for cross-ventilation and insulation specs that keep cooling costs down in July and August.
1-Bed & 2-Bed ADU
A 1-bedroom or 2-bedroom ADU adds privacy and rental value that a studio can’t match. You need this when the unit will house family long-term, when you’re targeting the rental market for working professionals, or when your Rialto property can support the larger footprint under current zoning. We size these units to the lot, not to a sales target. A 1-bedroom might run 500-650 square feet; a 2-bedroom typically needs 700-900 square feet plus parking per Rialto’s municipal code. The permit set includes every detail down to the egress window sizes, and the written price includes all of it.
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 New Detached ADU
We’ve specified and coordinated prefab and modular systems from Abodu, Plant Prefab, Tuff Shed, and James Hardie across dozens of projects in the Inland Empire. With Abodu, we’ve handled the site prep and utility tie-ins for their One and Two models on sloped lots in Fontana and Rialto, where the foundation design had to account for expansive soil conditions common to San Bernardino County. Plant Prefab’s panelized system allows more design flexibility than full modular, and we’ve integrated their LivingHome line into projects where the client wanted a custom kitchen layout with factory-built precision. Tuff Shed’s Pro Studio and Premier Pro lines are a cost-effective path for Rialto homeowners who need a permitted, habitable structure without the price tag of a full custom build. We handle the conversion from utility shed to dwelling unit, including the insulation, electrical, plumbing, and permit amendments.
James Hardie siding is our standard specification on custom builds in Rialto, where the summer sun and Santa Ana wind cycles punish lesser materials. We’ve installed Hardie Panel and HardiePlank on units from 400 to 1,000 square feet, and we know the fastening pattern and moisture barrier details that keep the warranty intact. Whether your project calls for Abodu, Plant Prefab, Tuff Shed, James Hardie, or any other system, we specify it, permit it, and build it under one contract at one written price.
Before
AfterSigns You Need New Detached ADU Right Now
- Your mortgage payment has become unsustainable. Rialto home prices rose sharply between 2019 and 2022, and many buyers in the 32-50 range are now carrying payments that strain monthly cash flow. A detached ADU generating $1,800-$2,400 in monthly rental income can restructure your household economics without selling at a loss.
- An aging parent needs proximity, not a nursing home. The cost of assisted living in San Bernardino County runs $4,500-$6,000 monthly. A 1-bedroom ADU on your Rialto property keeps family close for a fraction of that, and preserves the property’s value as a long-term asset.
- You work from home and need separation. The kitchen table stopped working two years ago. A studio ADU gives you a dedicated workspace with a door that closes, tax advantages if structured correctly, and the option to convert to rental if your situation changes.
- Your lot qualifies under Rialto’s current ADU ordinance but the rules are shifting. California’s state ADU laws preempt local restrictions, but Rialto’s specific implementation, including parking replacement and fire sprinkler triggers, gets adjusted as case law develops. Building now locks in your entitlements before any local amendment complicates your project.
- You have a written estimate from another firm that feels incomplete. A common tactic is to quote the structure low and add “allowances” for site work, utilities, and permits later. If your estimate doesn’t line-item every cost from demolition through final inspection, you’re exposed. We offer a Free Second Opinion on any written estimate already in hand.
Our New Detached ADU Process - Step by Step
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Site Survey & Feasibility. We measure your Rialto lot, photograph existing conditions, and pull the assessor’s parcel map to confirm setbacks, easements, and utility locations. You receive a written feasibility report with three layout options and a preliminary price range. No charge for this visit.
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Design & Permit Set. Once you select a direction, we produce architectural drawings, structural calculations, Title 24 energy compliance, and all Rialto Building Department forms. The permit set is the core product, not an afterthought. We submit and manage corrections until plans are approved.
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Fixed-Price Contract. With approved plans, we issue a written contract with every line item specified, from excavation to final paint. Haven Standard Clause 1 locks the price at signing. The scope is locked under Clause 5. No surprises, no change orders unless you request them.
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Construction & Documentation. Our crews build from the permitted drawings, and every site visit produces a documented photo record. You see what was found and what was done, not a summary of how it felt. If the framing doesn’t match the plans, we correct it before inspection.
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Inspection, Close-Out & Warranty. We schedule and pass all Rialto building inspections, including fire department sign-off if required. You receive keys, a final photo record, and the 365-Day Done Right Promise in writing. If it’s not built to the permitted drawings, we make it right.
How Much Does New Detached ADU Cost in Rialto?
A typical studio ADU in Rialto runs $220,000-$280,000 all-in, including design, permits, site work, and construction, per our New Detached ADU cost guide. A 1-bedroom unit typically costs $280,000-$350,000, and a 2-bedroom detached ADU runs $350,000-$420,000. Prefab and modular options can reduce these figures by 10-20% depending on the manufacturer and the complexity of your site.
| ADU Type | Size Range | Typical All-In Cost in Rialto |
|---|---|---|
| Studio ADU | 300-450 sq ft | $220,000-$280,000 |
| 1-Bedroom ADU | 500-650 sq ft | $280,000-$350,000 |
| 2-Bedroom ADU | 700-900 sq ft | $350,000-$420,000 |
| Custom Built (high finish) | Varies | Add 15-25% to above |
| Prefab/Modular | Varies | Subtract 10-20% from above |
What moves the price: soil conditions requiring engineered foundations, distance to sewer and water connections, fire sprinkler requirements triggered by proximity to the main house, and finish selections. What doesn’t move the price: our profit margin, which is fixed at signing. The best way to avoid overpaying is to get a written, line-item quote that includes every phase, not a “base price” with allowances that balloon later. Our free estimate covers the full scope. Call (951) 476-1467 to schedule yours.
New Detached ADU Near Rialto - Our Service Area
We design, permit, and build detached ADUs throughout the Inland Empire, including New Detached ADU in Fontana, New Detached ADU in San Bernardino, Rancho Cucamonga, Riverside, Redlands, Ontario, Eastvale, Upland, Moreno Valley, Montclair, and Chino. Typical initial site survey scheduling is within one week for Rialto properties. Permitting timelines vary by jurisdiction, San Bernardino County and the city of Rialto each have their own plan check queues, and we quote realistic permit timelines based on current backlog, not best-case scenarios.
Serving Rialto, CA - Our Local Coverage Area
We’re based in the Rialto 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 - New Detached ADU in Rialto
A new detached ADU is a separate, self-contained living unit built from the ground up on your property, not attached to your main house. It has its own foundation, walls, roof, kitchen, bathroom, and utility connections. In Rialto, detached ADUs are permitted up to 1,200 square feet on most single-family lots, subject to setback and height limits. Call (951) 476-1467 for a free feasibility survey of your specific lot.
From contract signing to move-in, a custom detached ADU in Rialto typically takes 12-18 months, with permitting consuming 4-8 months of that timeline. Prefab and modular options can compress construction to 6-10 months total. We quote realistic timelines per jurisdiction, and we don’t start construction until permits are in hand. Call (951) 476-1467 for a project schedule based on current Rialto Building Department turnaround.
A new detached ADU in Rialto costs $220,000-$420,000 all-in depending on size, construction type, and site conditions. Studios start at the lower end, 2-bedroom custom builds at the higher end. Every project gets a written, line-item price before any work begins, per Haven Standard Clause 1. Call (951) 476-1467 for an exact quote on your lot, estimates are free.
Yes. We specify and coordinate prefab and modular systems from Abodu, Plant Prefab, Tuff Shed, and other manufacturers within our single-contract design-build model. We handle the site prep, foundation, utility tie-ins, and finish work, while the manufacturer delivers the structure. The written price covers all of it. Call (951) 476-1467 to discuss which system fits your Rialto property.
ADU construction is planned work, not an emergency service, and we do not promise same-day or overnight response for new construction. A live person answers our phones 24/7 to schedule site surveys, answer questions about in-progress projects, or address urgent issues on active builds. For new detached ADU inquiries, we typically schedule your free feasibility visit within one week. Call (951) 476-1467 to get on the calendar.
We back every new detached ADU with the 365-Day Done Right Promise: if the finished unit is not built to the permitted drawings, we make it right, in writing, before your project starts. This is separate from and in addition to manufacturer warranties on appliances, fixtures, and prefab components. Call (951) 476-1467 to review the exact warranty language in our contract.
Gather your property’s assessor parcel number, a recent utility bill to confirm service locations, and any existing surveys or soil reports. If you have a written estimate from another firm, bring it for our Free Second Opinion. We’ll measure your lot, check setbacks against Rialto’s current zoning, and give you a preliminary price range and feasibility assessment during the visit. Call (951) 476-1467 to schedule.
Schedule Your New Detached ADU Service in Rialto Today
Call (951) 476-1467 to schedule your free estimate. A live person will answer, 24/7. You’ll receive a written, line-item price before any work begins, a documented photo record on every site visit, and the 365-Day Done Right Promise in writing. No voicemail queues, no callback promises that don’t materialize, no surprises once construction starts. Nadia Ellery and the team at Ellery ADU Studio Rialto are ready to walk your lot and give you the facts you need to make this decision.
Written by Nadia Ellery, Owner at Ellery ADU Studio, serving Rialto since 2015.