ADUByCity
Verified March 14, 2026

ADU Regulations in Ontario, California

San Bernardino County · CA · Pop. 190,000

Max ADU Size

1,200

sq ft detached

Rear Setback

4 ft

Permit Timeline

60 days

Build Cost

$115,000 – $240,000

Zoning

Allowed ADU Types

✓Detached ADU
✓Attached ADU
✓JADU (Junior ADU)
✓Garage Conversion
Max per lot: 2 ADUs✓ No owner-occupancy required

ADUs permitted by-right per California state law

Source: City of Ontario — Accessory Dwelling Units · Ontario Development Code Section 9-1.06.010

Dimensions

Size & Setback Requirements

Detached

1,200

sq ft max

JADU

500

sq ft max

Attached

50% of primary home, max 1,200 sq ft

Setbacks

front

Same as primary dwelling

side

4 ft

rear

4 ft

Max height: 16 ft

Lot coverage: Per underlying zone

Permitting

Permit Process

Department

Ontario Planning Department

Review Timeline

60 days

Permit Fees

$4,500 – $10,500

Impact Fees

Impact fees waived under 750 sq ft

Required Documents

  • ›Site plan
  • ›Floor plans
  • ›Elevations
  • ›Title 24 energy compliance
  • ›Structural drawings
Visit Ontario Planning Department →

Infrastructure

Utilities & Requirements

Solar

Required

Parking

Not required

Separate Meter

Optional

Fire Sprinklers

See note

Sewer: Inland Empire Utilities Agency; connect to existing lateral
Fire Sprinklers: Not required unless primary structure requires them
Parking: No additional parking required

Financials

ADU Costs in Ontario

Typical Build Cost

$115,000 – $240,000

Cost per Sq Ft

$165 – $230

Monthly Rental

$1,300 – $2,100/mo

Property Value Added

Adds $110,000 – $210,000 to property value

Available Grants & Programs

  • ★CalHFA ADU Grant Program available

Ontario Airport area rental demand supports consistent ADU occupancy

Use the free ADU Cost Calculator →

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Disclaimer: Information is compiled from publicly available municipal codes for general informational purposes only. It does not constitute legal, zoning, or construction advice. Regulations change frequently. Always verify with your local planning department. Last verified: March 14, 2026. Verify with Ontario Planning Department

Explore More

Nearby Cities in San Bernardino County

San Bernardino

Max 1,200 sq ft · $100,000 – $220,000

Fontana

Max 1,200 sq ft · $110,000 – $230,000

Rancho Cucamonga

Max 1,200 sq ft · $150,000 – $310,000

Victorville

Max 1,200 sq ft · $115,000 – $240,000

Rialto

Max 1,200 sq ft · $130,000 – $265,000

Hesperia

Max 1,200 sq ft · $115,000 – $235,000

Ontario Quick Facts

  • Max size1,200 sq ft
  • Rear setback4 ft
  • Permit timeline60 days
  • Build cost$115,000 – $240,000
  • Rental income$1,300 – $2,100/mo
  • Owner occupancyNot required

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Official Source

City of Ontario — Accessory Dwelling Units

Ontario Development Code Section 9-1.06.010

Last verified: March 14, 2026

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ADU rules change often.

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