ADU Before & After in Corona, CA
We’ve designed, permitted, and built over 900 ADUs since 2015. Every project starts with a written price and ends with a documented photo record. The transformations below show what that process actually looks like on real Corona properties: cluttered garages become rental units, bare backyards become income-producing studios, and awkward floor plans become functional junior ADUs.
Recent Transformations
Garage Conversion ADU: From Storage Dump to 485-Square-Foot Rental in Corona Hills
The Corona Hills homeowner had been parking outside for three years because the garage was unusable. We found the slab was 4 inches thick, which is within range for conversion, but the Zinsco panel had to go. Under Haven Standard Clause 1, we quoted $127,000 all-in - drawings through final inspection - before any work started. Nadia Ellery flagged the water heater location during the first site walk; moving it to a tankless exterior unit freed up 22 square feet of living space. The photo record from every visit went to the client automatically. The unit now rents for $1,850 per month.
New Detached ADU: Backyard Dirt Patch to 640-Square-Foot Two-Bedroom in South Corona
The South Corona lot had a 4-foot grade change from the alley to the main house. That’s a real problem for ADU siting because Corona’s setback variance - the extra distance the city requires between your new ADU and the property line - eats into buildable area on sloped lots. We brought in a geotechnical report that let us design a stem-wall foundation rather than a full flat pad, saving $14,000 on site prep. The Haven Standard written price was $214,000. We specified James Hardie siding and a mini-split system sized for Corona’s 100-degree summer peaks. The photo record shows every drainage layer, every inspection sign-off, and the final walkthrough.
Junior ADU & Interior Conversion: Awkward Bonus Room to Self-Contained Studio in Dos Lagos
The Dos Lagos homeowner wanted to house her mother but needed a self-contained unit. Junior ADUs in Corona can share utilities with the main house, but we recommended a separate meter because Southern California Edison’s baseline allowance is more generous with dual-meter properties. The existing room had one window; Corona’s fire code requires egress from sleeping areas, so we added a second operable window and a hardwired smoke/CO detector tied to the main panel. Written price: $67,000. The 365-Day Done Right Promise covers the permitted drawings exactly - if the finished ADU doesn’t match, we make it right in writing.
Garage Conversion ADU: Two-Car Garage to 520-Square-Foot One-Bedroom in Corona Ranch
The Corona Ranch garage had a 7.5-foot ceiling at the beam - too low for habitability under California’s ADU code, which requires 7 feet minimum but practically needs more for lighting and comfort. We engineered a flush beam replacement that gained 18 inches of headroom without touching the roofline. The oil-stained slab got a vapor barrier, rigid foam, and a floating subfloor system. Written price: $156,000. Nadia Ellery pointed out during the first walk that the existing driveway was 18 feet wide; Corona allows a 16-foot driveway for ADU properties, so we reclaimed 2 feet for a small patio. The photo record shows the beam install, the foam layers, and the final inspection sticker.
ADU Site Prep & Utilities: Unbuildable Slope to Ready Pad in Sierra Del Oro
The Sierra Del Oro property looked unbuildable. The previous contractor had walked away after discovering the fill was undocumented - Corona’s building department requires a geotechnical report for any structure on slopes over 15 percent. We brought in a soils engineer, designed a segmental retaining wall with drainage, and specified a sewage ejector system because gravity flow to the main sewer was impossible. The overhead SCE lines had to be undergrounded for the ADU’s service drop; we coordinated that trench with the sewer and water lines in one pull. Written price for site prep and utilities alone: $89,000. The photo record includes every soils boring log, every wall course, and the final utility sign-off. The client is now building a Cover prefab unit on the pad under a separate Haven Standard contract.
New Detached ADU: Prefab Coordination - Abodu One Module in Trilogy
The Trilogy HOA required architectural compatibility - same stucco texture, same roof tile profile, same paint color family. We specified the Abodu One with a custom exterior package and handled the HOA submittal, the city permit, and the site prep under one contract. The module arrived on a flatbed at 6 a.m.; by 4 p.m. it was craned onto the foundation and weather-tight. Corona’s fire department required a 10-foot access path for emergency vehicles; we designed the landscaping to maintain that width permanently. Written price: $198,000 including the module, site work, and all finish connections. The photo record shows the crane set, the utility connections, and the final HOA sign-off.
Want Results Like These?
Every project above started the same way: a site walk, a written price under Haven Standard Clause 1, and a documented photo record from day one. No call-for-a-quote runaround. No surprise invoices. Call (951) 476-3715 to schedule your free estimate. Already have a written estimate in hand? We’ll give you a free second opinion.
Written by Nadia Ellery, Owner at Ellery ADU Studio Corona, serving Corona since 2015.