Frequently Asked Questions

From signed contract to certificate of occupancy, expect 12 to 18 months. Design and permitting in Corona typically takes 4 to 6 months, depending on plan check queue depth. Construction runs 8 to 12 months for a detached unit. We've seen faster in Riverside County when using pre-approved plans, and slower when slope or utility complications arise in the hills above Norco. We give you a real schedule, not a sales number, and text you when each milestone hits.

A design-build studio holds one contract for design, permits, and construction. A traditional contractor builds from plans you got elsewhere, and when the drawings don't match field conditions, the designer and builder blame each other while you pay for fixes. Since 2015, we've handled both sides because the ADU projects that fail are almost always the ones split between two parties. One price. One responsible party. That's the point.

Yes. We pull all permits and meet all inspections as part of our flat fee. Corona uses the Riverside County building department for some inspections and handles others in-house; we know which is which and schedule accordingly. You don't chase inspectors or resubmit plans. We document every inspection pass with photos and report back to you. Permits pulled and inspections passed - it's in writing.

Yes, though slope adds cost and engineering complexity. Lots in the foothills near Chino Hills state park, the terrain above Mira Loma, and sections of Temescal Valley often need retaining walls, stepped foundations, or specialized drainage. We evaluate slope, soils, and access during our initial site visit and price for the actual conditions, not a flat-lot assumption. If your lot is steep, we'll tell you exactly what it means for budget and timeline.

Usually not. Most of our Corona builds are detached units in the backyard, so your main house stays fully occupied. Attached garage conversions require access to your existing structure, but we sequence the work to minimize disruption. We'll show you the phasing plan before we start so you know which weeks are loud, which need utility shutoffs, and when you'll have workers on site.

We specify Boxabl and Plant Prefab for clients who want factory-built modules delivered to site, and we use James Hardie siding on most of our stick-built ADUs for its fire rating and durability in Corona's heat. Each brand fits different sites: Boxabl units work well on flat, accessible lots in Eastvale and Pedley; Plant Prefab offers more customization for hillside access challenges. We don't push one solution - we match the product to your lot, your budget, and your design goals.

Sometimes, but not always. Factory-built units save on labor and weather delays, but delivery crane costs, foundation work, and utility tie-ins in Corona can offset those savings. On tight infill lots in Home Gardens or El Sobrante, a site-built ADU with Tuff Shed components for storage may pencil out better. We price both paths honestly and show you the breakdown. The cheaper option depends on your specific site, not the marketing.

Corona's 100-plus summer days and Santa Ana wind events punish cheap materials. We specify James Hardie fiber-cement siding for fire resistance and thermal stability, dual-pane low-E vinyl windows for the inland heat, and cool-roof shingles that reflect rather than absorb. For foundation work, we account for the clay-heavy soils in parts of Riverside County that expand and contract with seasonal moisture. We build for what Corona actually does to a structure.

Yes. Every pro working under our name in Corona is required to hold the license and insurance California requires for residential construction. Nadia Ellery leads our local branch, and we verify crew credentials before they step on your property. License numbers appear on every contract, and we carry the general liability and workers compensation coverage your lender and the city will ask for.

Ellery ADU Studio is an established design-build brand founded in 2015. Our Corona branch is independently owned and operated by Nadia Ellery, with local trucks, local crews, and local knowledge of Riverside County's permit landscape. What the brand contributes is the Haven Standard - the documentation system, the flat-price model, and the buying power that keeps material costs honest. The local business is the franchisee; the standard is what we all work to.

Our core crew lives and works in the Corona-Norco-Riverside corridor. We don't fly in teams from Los Angeles or San Diego who don't know local soil conditions or which Riverside County inspector handles foundation checks. For specialized trades - electrical, plumbing, HVAC - we use local subcontractors we've worked with repeatedly, each vetted under our Haven Standard. You get consistency, not a rotating cast.

We document what we found, fix what we broke, and don't hide from problems. Clause 4 of the Haven Standard - "Evidence on every job" - means photos and readings of actual conditions, so disputes don't devolve into he-said-she-said. If we hit unexpected bedrock in Chino Hills, we show you the photo, explain the options, and price the change before we proceed. No surprises means no surprises, including the hard conversations.

Our phone is answered 24/7 by a live coordinator who connects you with the local team. For urgent safety issues - a trench collapse, exposed electrical, gas line strike - we escalate immediately. For non-urgent questions, you'll get a callback from your project lead by the next business day. We don't vanish after the contract is signed. The same number reaches us throughout your build: (951) 476-3715.

We fix it at our cost. Permit rejections happen - Riverside County plan checkers are thorough, and Corona's zoning overlay has quirks we navigate regularly. Our flat price includes all resubmissions and corrections. We don't charge you because a plan checker wanted a clearer fire separation detail or an updated energy calculation. This is why we do design and permits in-house: we control the loop.

Every ADU we build carries a written workmanship warranty, documented in your contract before we start. Structural elements, waterproofing, and mechanical systems are covered for periods we specify in writing - no handshake promises. Clause 1 of the Haven Standard requires the warranty terms in the same document as your price. If we won't put it in writing, we won't say it.

The Haven Standard is our five-clause operating framework, not a marketing phrase. Have it in writing - flat price, written scope, written warranty before anyone starts. Arrive on schedule - real windows, named crews, texts when we're en route. Verified crews - licensed, insured, background-checked. Evidence on every job - photos and readings of what we found. No surprises - no upsell, no scope creep, no "while we're in here." Every ADU job is quoted in writing before it starts and leaves a documented record. That's the promise.

Yes. Our workmanship warranty transfers to the new owner with documentation of the original scope, photos, and inspection records. This matters in Corona's market, where ADUs add significant resale value and buyers want proof the unit was built to code. We provide the paper trail that protects your investment and makes your disclosure package stronger. Call (951) 476-3715 and we'll explain what's covered and for how long.

Call (951) 476-3715 to schedule a free site evaluation. Nadia Ellery or a member of our local team will walk your lot, check access and utilities, and give you a real price range with no obligation. If you move forward, we handle design, permits, and build under one flat contract. We've been doing this in Corona since 2015 - permitted, built, and finished to the drawings.

Written by Nadia Ellery, Owner at Ellery ADU Studio Corona, serving Corona, El Cerrito, Home Gardens, Norco, El Sobrante, Eastvale, Mira Loma, Temescal Valley, Chino, Pedley, Chino Hills, and Riverside since 2015.