ADU Regulations in Fullerton, California
Orange County · CA · Pop. 140,000
Max ADU Size
1,200
sq ft detached
Rear Setback
4 ft
Permit Timeline
60 days
Build Cost
$160,000 – $330,000
Zoning
Allowed ADU Types
ADUs are permitted by right on any lot with a single-family or multifamily dwelling in all residential zones. Fullerton's older R-1 neighborhoods near the two colleges have many lots with underutilized rear yards and detached garages, making them especially well-suited for ADU development.
Source: City of Fullerton — Accessory Dwelling Units · Fullerton Municipal Code Chapter 15.50 (Accessory Dwelling Units)
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 (detached); up to 25 ft if attached or above garage
Lot coverage: Per underlying zone; R-1 typically 40–45%
Fullerton's hillside neighborhoods (e.g., Sunny Hills area) may require additional grading review for detached ADUs. Lots near the Fullerton Transportation Center that are zoned R-2 or R-3 can accommodate up to two ADUs plus the primary structure.
Permitting
Permit Process
Department
Community and Economic Development — Planning Division
Review Timeline
60 days
Permit Fees
$8,000 – $16,000
Impact Fees
Impact fees waived for ADUs under 750 sq ft; school fees assessed by Fullerton School District and Fullerton Joint Union High School District separately
Required Documents
- ›Site plan with lot dimensions, setbacks, and utility connections
- ›Floor plans
- ›Elevations
- ›Title 24 energy compliance
- ›Structural drawings
- ›Grading/drainage plan (if applicable)
Fullerton offers an ADU pre-application consultation at no charge. The Planning Division has published an ADU handout outlining the submittal checklist; available on the city's website. Orange County Fire Authority provides fire/life-safety review.
Visit Community and Economic Development — Planning Division →Infrastructure
Utilities & Requirements
Solar
Required
Parking
Not required
Separate Meter
Optional
Fire Sprinklers
See note
Financials
ADU Costs in Fullerton
Typical Build Cost
$160,000 – $330,000
Cost per Sq Ft
$225 – $300
Monthly Rental
$1,700 – $2,700/mo/mo
Property Value Added
Adds $155,000 – $300,000 to property value
Available Grants & Programs
- ★CalHFA ADU Grant Program available (up to $40,000 for pre-development costs)
- ★Orange County Housing Finance Trust programs
Cal State Fullerton (40,000+ students) and Fullerton College (20,000+ students) create persistent rental demand within walking or biking distance of campus. ADUs targeting the student rental market often achieve occupancy rates above 95%, making them among the most reliable income-producing ADUs in Orange County.
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Fullerton Quick Facts
- Max size1,200 sq ft
- Rear setback4 ft
- Permit timeline60 days
- Build cost$160,000 – $330,000
- Rental income$1,700 – $2,700/mo/mo
- Owner occupancyNot required
Official Source
City of Fullerton — Accessory Dwelling UnitsFullerton Municipal Code Chapter 15.50 (Accessory Dwelling Units)
Last verified: March 14, 2026
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