Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your Corona ADU cost →Building an ADU in Corona costs between $160,000-$300,000 for new construction, with per-square-foot costs averaging $200-$350. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $70,000-$150,000, while prefab/modular ADUs fall in between at $80,000-$180,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & Fees | Plan check fees set by City Council resolution, paid at submittal — confirm current amounts with Corona Planning & Development, (951) 736-2262 |
| Impact Fees | Waived under 750 sq ft per state law; new attached/detached ADUs pay a water and sewer connection fee/capacity charge proportionate to square footage or fixture units; JADUs and interior conversions exempt |
| Site Prep & Foundation | $10,000 – $35,000 |
| Framing & Structure | $15,000 – $45,000 |
| Plumbing | $8,000 – $20,000 |
| Electrical | $5,000 – $15,000 |
| HVAC | $3,000 – $8,000 |
| Interior Finishes | $15,000 – $40,000 |
Quotes for the same ADU commonly vary 20–40% between builders. Get up to 3 free quotes from ADU builders serving Corona — no obligation.
Get Corona builder quotes →Permit fees in Corona are Plan check fees set by City Council resolution, paid at submittal — confirm current amounts with Corona Planning & Development, (951) 736-2262. The review timeline is City must act within 60 days of a complete application (Chapter 17.85.060; SB 543 deemed-approval backstop applies from 2026), with plan check: Standard Building Division plan-check submittal; ADU must be architecturally compatible with the primary unit (style, roof pitch, color, exterior materials); fire sprinklers only if the primary unit requires them. Impact fees are Waived under 750 sq ft per state law; new attached/detached ADUs pay a water and sewer connection fee/capacity charge proportionate to square footage or fixture units; JADUs and interior conversions exempt. Pre-approved plans: No city pre-approved plan program identified — confirm with the Planning Division (Riverside County's free Permit Ready ADU plans apply to unincorporated areas, not the City of Corona).
| 1-Bedroom Rent | $1,950-$2,250/month |
| 2-Bedroom Rent | $2,350-$2,750/month |
| Annual Rental Income (est.) | $25,200/year |
| Payback Period (est.) | 9.1 years |
| Short-Term Rental | No — rentals under 30 days are prohibited for both the ADU and the primary unit on the lot |
| Overall ROI Estimate | 7-10% annual return (gross rental yield estimate) |
A typical ADU in Corona generates approximately $25,200 per year in rental income based on average 1-bedroom rents. At an average construction cost of $230,000, the estimated payback period is 9.1 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in Corona and varies by market (often less than build cost).
1. Garage conversions save 40-60% vs new construction since the shell already exists. Average cost in Corona: $70,000-$150,000.
2. Prefab/modular ADUs offer predictable pricing and faster timelines. Average: $80,000-$180,000.
3. Pre-approved plans — Corona does not offer a pre-approved/standard ADU plan program yet, so budget for custom architectural plans (typically $3,000-$15,000).
4. State grants — California's CalHFA ADU grant (up to $40K) is currently paused; check calhfa.ca.gov/adu for status and your state for active programs.
5. Get multiple bids — ADU contractor pricing varies 20-40% for the same project. We recommend getting at least 3 quotes.
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