Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your Corona ADU cost →Building an ADU in Corona costs between $180,000-$320,000 for new construction, with per-square-foot costs averaging $180-$300. 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 $120,000-$250,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & Fees | $2,466 for a garage-to-ADU conversion (plan check $1,383.61 + inspection $1,082.60; $2,684 from Oct 4, 2026 under Res. 2026-085) and up; a new ADU is priced per sq ft as new single-family construction (Table A: $3,611 at 2,000 sq ft, Type V-B) plus 5% General Plan maintenance. |
| Impact Fees | The city's DIF schedule effective 7/1/2026 lists no city impact fee for ADUs except the MSHCP habitat fee, prorated for ADUs of 750 sq ft or more ($4,632 x ADU sq ft / house sq ft); ADUs of 750 sq ft or less are exempt from all impact fees under Gov. Code 66311.5(c). A new attached or detached ADU pays a sewer capacity charge (Development Services rates a secondary unit at 200 gpd x $15.48 = $3,096) and a water capacity charge proportionate to its size or fixture units (CMC 17.85.030(G)); JADUs and conversions of existing living area are exempt (17.85.030(F), 17.85.050(J)). TUMF is paid to WRCOG and school fees to Corona-Norco USD; confirm both with Development Services, (951) 736-2259. |
| 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. We pass your request to up to 5 local builders serving Corona, where we have them — free, no obligation.
Get Corona builder quotes →Permit fees in Corona are $2,466 for a garage-to-ADU conversion (plan check $1,383.61 + inspection $1,082.60; $2,684 from Oct 4, 2026 under Res. 2026-085) and up; a new ADU is priced per sq ft as new single-family construction (Table A: $3,611 at 2,000 sq ft, Type V-B) plus 5% General Plan maintenance.. The review timeline is The city must act within 60 days of a complete application (CMC 17.85.060; Gov. Code 66317 deemed-approval backstop). Published Building Division targets (ADU flow chart, March 2026): first review 10 business days, rechecks 5, plus 2 days processing and 3 days to issue the permit., with plan check: Submit through eTRAKiT with the Building Plan Check Submittal Checklist; structural plans must come from a licensed architect or engineer unless the unit is conventional wood-frame construction of two stories or less; plot easements and overhead-line clearances (GO 95); fire sprinklers only if the main house requires them (CMC 17.85.040(J)); the ADU must match the main house in style, roof pitch, color and exterior materials (17.85.040(I)); a separate entrance is required (17.85.040(G)).. Impact fees are The city's DIF schedule effective 7/1/2026 lists no city impact fee for ADUs except the MSHCP habitat fee, prorated for ADUs of 750 sq ft or more ($4,632 x ADU sq ft / house sq ft); ADUs of 750 sq ft or less are exempt from all impact fees under Gov. Code 66311.5(c). A new attached or detached ADU pays a sewer capacity charge (Development Services rates a secondary unit at 200 gpd x $15.48 = $3,096) and a water capacity charge proportionate to its size or fixture units (CMC 17.85.030(G)); JADUs and conversions of existing living area are exempt (17.85.030(F), 17.85.050(J)). TUMF is paid to WRCOG and school fees to Corona-Norco USD; confirm both with Development Services, (951) 736-2259.. Pre-approved plans: None. Corona publishes no pre-approved or permit-ready ADU plan set on its Building or Planning pages (checked 9/20/2026); ask the Building Division, (951) 736-2250, whether a program under Gov. Code 65852.27 exists. Riverside County's Permit Ready ADU plans are a county program for unincorporated areas and do not apply inside the city..
| 1-Bedroom Rent | $1,800-$2,150/month |
| 2-Bedroom Rent | $2,350-$2,600/month |
| Annual Rental Income (est.) | $23,700/year |
| Payback Period (est.) | 10.5 years |
| Short-Term Rental | No. Rentals shorter than 30 days are prohibited for both the ADU and the primary unit on the lot (CMC 17.85.030(E)); the same 30-day floor applies to a JADU and its main house (17.85.050(C)). |
| Overall ROI Estimate | 6-11% gross rental yield on a $180,000-$320,000 detached build at $1,800-$2,600/mo; roughly 14-30% gross on a $70,000-$150,000 garage conversion; before vacancy, taxes and financing |
A typical ADU in Corona generates approximately $23,700 per year in rental income based on average 1-bedroom rents. At an average construction cost of $250,000, the estimated payback period is 10.5 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: $120,000-$250,000.
3. Pre-approved plans — available in Corona, which can save $3,000-$10,000 in design costs and 2-3 months in review time. See which cities offer pre-approved ADU plans.
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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