How big can an ADU be in Fontana?

Detached ADUs in Fontana can be up to 1,200 sq ft. Attached ADUs: 50% of primary home, max 1,200 sq ft. JADUs up to 500 sq ft.

How much does it cost to build an ADU in Fontana?

Build costs typically range $110,000 – $230,000, or $160 – $230 per square foot.

Verified March 14, 2026

ADU Regulations in Fontana, California

Q: What are the setback requirements for ADUs in Fontana?

Front: Same as primary dwelling. Side: 4 ft. Rear: 4 ft.

San Bernardino County · CA · Pop. 215,000

Max ADU Size

1,200

sq ft detached

Rear Setback

4 ft

Permit Timeline

60 days

Build Cost

$110,000 – $230,000

Zoning

Allowed ADU Types

✓Detached ADU

✓Attached ADU

✓JADU (Junior ADU)

✓Garage Conversion

Max per lot: 2 ADUs✓ No owner-occupancy required

ADUs allowed by-right per California state law

Source: City of Fontana — Accessory Dwelling Units · Fontana Municipal Code Chapter 30

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

Fontana's newer subdivisions often have HOA restrictions — check CC&Rs before applying

Permitting

Permit Process

Department

Fontana Community Development Department

Review Timeline

60 days

Permit Fees

$4,500 – $10,000

Impact Fees

Impact fees waived under 750 sq ft

Required Documents

›Site plan
›Floor plans
›Elevations
›Title 24 energy compliance
›Structural drawings

HOA approval is separate from city permits and not required by law, but recommended

Visit Fontana Community Development Department →

Infrastructure

Utilities & Requirements

Solar

Required

Parking

Not required

Separate Meter

Optional

Fire Sprinklers

See note

Sewer: Fontana Water Company service area; connect to existing lateral

Fire Sprinklers: Not required unless primary structure requires them

Parking: No additional parking required

Financials

ADU Costs in Fontana

Typical Build Cost

$110,000 – $230,000

Cost per Sq Ft

$160 – $230

Monthly Rental

$1,300 – $2,100/mo

Property Value Added

Adds $100,000 – $200,000 to property value

Available Grants & Programs

★CalHFA ADU Grant Program available

Inland Empire labor costs keep construction affordable relative to coastal cities

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 Fontana Community Development Department

Explore More

Nearby Cities in San Bernardino County

San Bernardino

Max 1,200 sq ft · $100,000 – $220,000

Ontario

Max 1,200 sq ft · $115,000 – $240,000

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

Fontana Quick Facts

Max size1,200 sq ft
Rear setback4 ft
Permit timeline60 days
Build cost$110,000 – $230,000
Rental income$1,300 – $2,100/mo
Owner occupancyNot required

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Official Source

City of Fontana — Accessory Dwelling Units

Fontana Municipal Code Chapter 30

Last verified: March 14, 2026

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ADU rules change often.

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