ADU Before & After in Chino Hills, CA
We’ve completed over 900 ADU projects since 2015, and every one started with a problem someone was living with. Below are representative transformations across the five services we offer in Chino Hills. Each project follows the same protocol: written price before work starts, documented photo record on every visit, and our 365-Day Done Right Promise in writing.
Recent Transformations
Garage Conversion ADU: Double-Car to 480-Square-Foot Rental in Vellano
The homeowner had a 20-by-24-foot garage in Vellano collecting storage bins and holiday decorations. The slab was 4 inches, within range for conversion; here is what that meant for the foundation line item: no new pour required, saving roughly $8,000-$12,000 against a ground-up build. We submitted a 4070 form to Chino Hills Building & Safety for the change of occupancy, ran a new electrical service lateral from the existing panel (upgraded to 400-amp), and installed a wet wall with 2-inch drain lines tied to the main sewer at the front corner of the house. The roll-up door was infilled with framed wall, moisture barrier, and stucco to match the existing elevation. Under Clause 5 (No Surprises), the scope was locked at signing; no door-side upsells, no scope creep. The client received the permit set, a photo record of every rough-in inspection, and a written warranty. Garage conversion ADUs in Chino Hills typically run $145,000-$195,000 all-in, drawings through final inspection.
New Detached ADU: Backyard Studio in Oak Tree Downs
The Oak Tree Downs lot had a protected coast live oak that eliminated about 40 percent of buildable area under Chino Hills Municipal Code Chapter 16.58. We brought in a certified arborist for the tree protection plan, then designed a pier foundation system that avoided root zones entirely. The grade change meant we needed a stepped foundation with retaining walls; we used segmental block rather than poured concrete to reduce vibration during construction. The client wanted a modern line, so we specified James Hardie Panel with a rainscreen assembly for the exterior. New detached ADUs in Chino Hills typically run $220,000-$310,000 all-in, drawings through final inspection, depending on foundation complexity and utility trenching length. The permit set included the arborist report, soils compaction data, and the photo record from every inspection pass.
Junior ADU & Interior Conversion: Attached Studio in Butterfield Ranch
This Butterfield Ranch homeowner had a bonus room over the garage with its own door to the side yard. The catch: junior ADUs in California require exterior access and must be within the existing footprint. We confirmed the room met the 500-square-foot maximum and designed an efficiency kitchen with a 2-burner cooktop and compact refrigerator under counter. The existing 3/4 bath needed ADA-turning-radius revision; we bumped one wall 14 inches into an adjacent storage nook. A critical detail in Chino Hills: junior ADUs can share sewer and water with the main house but require separate electrical metering if the owner wants rental income documentation. We installed a submeter with wireless readout. The client received the revised floor plan, the photo record showing fire-rated drywall at the shared wall, and the written scope under Haven Standard Clause 1. Junior ADU conversions in Chino Hills typically run $85,000-$135,000 all-in, drawings through final inspection.
ADU Site Prep & Utilities: Hillside Lot in Sleepy Hollow
The Sleepy Hollow property had a beautiful view and a brutal building condition. We started with a geotechnical report that identified a shallow groundwater table at 8 feet during spring, which meant standard spread footings would need drainage below grade. Our solution: a combination of drilled piers to 12 feet and a suspended slab with crawl space ventilation. The 180-foot utility run required trenching through the front yard and under the existing driveway; we pulled a separate encroachment permit from the city and coordinated with Southern California Edison for the transformer sizing. Site prep and utilities in Chino Hills typically run $45,000-$85,000 as a standalone scope, though most clients bundle this into a full design-build contract. The documentation package included the geotechnical report, the pier log, the photo record of every footing inspection, and the written warranty for the retaining wall drainage system.
Garage Conversion ADU: Tandem Three-Car to Two-Bedroom in Los Serranos
The Los Serranos homeowner had a deep tandem garage that fit three cars in theory and two in practice. The 10-foot ceiling gave us headroom for a dropped soffit with ducted mini-split supply lines. Because Chino Hills requires replacement parking for any converted garage, we designed a new carport at the driveway’s side setback; the permit set included the site plan showing the 18-by-20-foot covered structure. The existing slab had a crack pattern indicating minor settlement; we specified epoxy injection and a floating LVT floor system rather than tile, which would telegraph any future movement. Two-bedroom garage conversions in Chino Hills typically run $175,000-$235,000 all-in, drawings through final inspection. The client received the full permit set, the photo record from pre-construction through final, and the 365-Day Done Right Promise in writing before anyone picked up a tool.
New Detached ADU: Prefab Coordination in Rolling Ridge
The Rolling Ridge client wanted speed and certainty. We specified an Abodu One unit, which ships pre-finished with MEP rough-in complete. Our role was site prep, foundation, utility tie-in, and finish coordination. The Abodu arrived on a flatbed at 7 a.m.; by 3 p.m. it was set on the pier foundation we’d poured the week prior. The critical path was Chino Hills Building & Safety: modular units require a state HCD insignia plus local foundation and utility inspection. We handled both tracks, including the HCD 433 form for factory-built housing. Prefab and modular projects in Chino Hills typically run $195,000-$285,000 all-in depending on unit specification and site complexity. The client received the HCD documentation, the local permit set, the photo record of crane set and utility connection, and the written warranty covering both factory and site-built components under our single contract.
Want Results Like These?
Every project above started with a free estimate and a written price before any work began, per Haven Standard Clause 1. If you have a written estimate from another firm, we’ll give you a free second opinion. Call (951) 456-4467 to schedule your free estimate. A live person answers calls 24/7, and Nadia Ellery reviews every scope before it goes out.
Written by Nadia Ellery, Owner at Ellery ADU Studio Chino Hills, serving Chino Hills since 2015.