California ADU Expertsby JBC Design & Build
We design, engineer, permit, and build custom ADUs across Riverside and San Bernardino counties — from Fontana and Ontario to Riverside, Corona, and Temecula. One integrated team, transparent pricing, no contractor juggling.
Riverside is the county seat and the largest city in Riverside County, and it has the housing stock that makes ADUs work: deep lots, detached garages, and single-story homes built when land was cheap and setbacks were generous. A backyard that looks like nothing but grass is often the easiest ADU site we see.
Yes, you can build an ADU on most Riverside properties. Under California state ADU law (Gov. Code §66310 et seq., administered by California’s Department of Housing and Community Development), ADUs are allowed on nearly all single-family and multifamily lots statewide, a detached ADU can generally be up to 1,200 square feet, and your city or county must approve or deny a complete application within 60 days.
JBC Design & Build handles the entire process in the Riverside — feasibility, design, engineering, permits, and construction — so you deal with one team from first sketch to final inspection. Below you’ll find typical costs, timelines, the cities we serve, and answers to the questions homeowners ask most.
Source: California ADU law (Gov. Code §66310 et seq.), California Department of Housing and Community Development (HCD).
Riverside properties tend to have larger yards than coastal LA and Orange County, which often means room for a full detached ADU rather than a small conversion.
Cities like Riverside, San Bernardino, Fontana, and Corona have steady long-term rental demand, so an ADU can generate income and help offset your mortgage.
California’s statewide ADU rules require ministerial (non-discretionary) approval and cap review at 60 days, which keeps Riverside permitting more predictable than it used to be.
In the Riverside, most detached ADUs typically range from the low $100,000s to $300,000+, depending on size, finishes, and site conditions. Conversions and junior units usually cost less because they reuse existing structure. Here is how the three main ADU types compare.
| ADU type | What it is | Typical size | Typical Riverside cost | Typical timeline |
|---|---|---|---|---|
| Detached ADU | A standalone backyard home, fully independent of the main house. | Up to 1,200 sq ft | Low $100Ks – $300K+ | 7–14 months |
| Garage conversion | Converts an existing garage into a legal living unit. | ~400–800 sq ft | Lower — reuses structure | 5–10 months |
| Junior ADU (JADU) | A small unit created within the walls of your existing home. | Up to 500 sq ft | Lowest of the three | 4–8 months |
Ranges are typical estimates for planning only and vary by lot, city, and finishes. After your free feasibility review, we provide clear, fixed pricing with no hidden fees.
Share your Riverside address so we can check zoning, setbacks, and utilities against your city’s ADU rules — and tell you honestly what your lot can build.
Our in-house team designs a custom ADU tailored to your lot, goals, and budget, so the plan fits your property and your numbers.
We prepare engineered plans and submit them to your city or county building department, managing corrections and approvals for you.
One integrated crew builds the ADU from foundation to final finishes — no subcontractor runaround.
We pass final inspection, secure your certificate of occupancy, and hand you the keys.
Riverside pairs a large rental market with older, larger parcels. Homes around the Wood Streets, Victoria and Arlington Heights were platted with room behind them, and many still have an original detached garage — which state law lets you convert or replace without the lot ever feeling crowded. Proximity to UCR and RCC keeps demand for smaller units steady year-round.
“I highly recommend JBC Design & Build Co. Joe and his team have renovated many of my properties and have done an excellent job. Their pricing is very reasonable and they are efficient and fast.”
“I recently had my kitchen remodeled and I wanted to acknowledge JBC Design & Build for the excellent work they did. Joe was very professional and quick in providing an estimate.”
“JBC Design and Build have been doing my architectural designs for years. Very professional and always on time. They also build all of my ADUs in the area. Quality workmanship.”
“Joe and his crew built a multimillion-dollar house that I designed and everything turned out great. Our client was very happy with his work.”
In the Riverside, most detached ADUs typically range from the low $100,000s to $300,000+ depending on size, finishes, and site conditions. Garage conversions and junior ADUs usually cost less because they reuse existing structure. After a free feasibility review, we provide transparent, fixed pricing with no hidden fees.
Yes. Every ADU in Riverside County and San Bernardino County requires a building permit. Under California state ADU law, your city or county must review a complete application ministerially and approve or deny it within 60 days. We prepare the plans and manage the entire permit process for you.
We serve the full Riverside, including Riverside, San Bernardino, Fontana, Ontario, Rancho Cucamonga, Corona, Moreno Valley, Rialto, Redlands, Chino, Chino Hills, Upland, Colton, Jurupa Valley, Eastvale, Menifee, Murrieta, Temecula, Hemet, and Yucaipa.
Design and permitting typically take 3 to 6 months, and construction another 4 to 8 months, depending on size and city. Because we handle design, engineering, and construction in-house, we keep the timeline tight.
Under California state ADU law, a detached ADU can generally be built up to 1,200 square feet, and a junior ADU up to 500 square feet within an existing home. Local rules and lot conditions can affect the buildable size, which we confirm during your feasibility review.
Yes. Riverside ADUs are commonly rented for long-term income and can meaningfully increase property value. Actual rent depends on size, location, and finishes.
Under current California state ADU law, standard ADUs are approved ministerially and do not require the owner to live on site. A junior ADU (JADU) does require owner-occupancy. Rules can change, so we confirm the current requirement for your city during your free review.
In most cases, yes. A permitted, well-built ADU adds livable square footage and potential rental income, both of which support property value in the Riverside market.
Answer a few quick questions and our team will review your lot, check your city’s ADU rules, and send back a no-pressure feasibility snapshot with real numbers.
Get a free, no-obligation ADU feasibility review with real rental and value estimates for your property.
Get My Free Review