Orange County ADU Regulations by City
Every Orange County city has slightly different ADU requirements. Use this guide to understand your city's specific rules for size, height, setbacks, and permits.
Note: Regulations change frequently. This guide reflects 2024-2025 rules but always confirm with your local planning department. We handle all permit research as part of our design-build service.
Quick Reference Table
| City | Max Size | Height | Setbacks | Parking | Estimated Permit Review Time |
|---|---|---|---|---|---|
| Anaheim | 1,200 sq ft | 18 ft | 4 ft rear/side | 1/bedroom max | 4-6 weeks |
| Buena Park | 1,000 sq ft | 15 ft | 4 ft rear/side | 1 space (exemptions available) | 4-6 weeks |
| Costa Mesa | 1,200 sq ft | 18 ft | 4 ft rear/side | None near transit | 4-6 weeks |
| Fountain Valley | 1,000 sq ft | 18 ft | 4 ft rear/side | 1 space (exemptions available) | 4-6 weeks |
| Fullerton | 1,200 sq ft | 16 ft | 4 ft rear/side | 1 space (exemptions) | 4-6 weeks |
| Garden Grove | 1,200 sq ft | 16 ft | 4 ft rear/side | 1 space (exemptions near transit) | 4-6 weeks |
| Huntington Beach | 1,200 sq ft | 16 ft | 4 ft rear/side | None near transit | 4-8 weeks |
| Irvine | 1,200 sq ft | 16 ft | 4 ft rear/side | 1/bedroom (transit exempt) | 4-6 weeks |
| Santa Ana | 1,000 sq ft | 16 ft | 4 ft rear/side | 1 space (many exemptions) | 2-4 weeks with pre-approved plans |
| Stanton | 1,000 sq ft | 16 ft | 4 ft rear/side | 1 space (exemptions available) | 4-6 weeks |
| Tustin | 1,200 sq ft | 16 ft | 4 ft rear/side | 1 space (exemptions) | 4-6 weeks |
| Westminster | 1,200 sq ft | 16 ft | 4 ft rear/side | 1 space (transit exemptions) | 4-6 weeks |
| City of Orange | 1,000 sq ft | 16-25 ft | 4 ft rear/side | Standard | 4-8 weeks |
| Laguna Beach | 850-1,000 sq ft | 16-18 ft | 4 ft + 25 ft from bluff | Standard | 8-12 weeks |
| Rancho Santa Margarita | 800 sq ft | 16-25 ft | 4 ft rear/side | Standard | 4-6 weeks |
| Mission Viejo | 1,200 sq ft | 16-25 ft | 4 ft rear/side | 1 space (exemptions) | 4-6 weeks (plus HOA) |
| Lake Forest | 1,200 sq ft | 16-25 ft | 4 ft rear/side | Standard | 4-6 weeks |
Detailed City Requirements
Anaheim
2 stories allowed. Historic property districts have additional design standards. Standard residential zones allow straightforward ADU construction.
Special Considerations:
Buena Park
1 story only. Standard compliance with efficient permit process.
Special Considerations:
Costa Mesa
Recently updated ADU ordinance (2024) following HCD review. More flexible than before.
Special Considerations:
Fountain Valley
ADU-friendly city with efficient permit process. We've completed multiple luxury ADU projects here including the featured Pelican ADU.
Special Considerations:
Fullerton
No impact fees for ADUs, making it one of the more affordable cities to build in.
Special Considerations:
Garden Grove
One of our most active markets. Garden Grove has embraced ADU development with reasonable permit timelines and standard requirements.
Special Considerations:
Huntington Beach
Coastal Zone permits required for beach-adjacent properties. Recent ordinance updates have streamlined the process.
Special Considerations:
Irvine
All residential zones eligible. HOA review may be required in master-planned communities. Clear guidelines and efficient permit process.
Special Considerations:
Santa Ana
One of the most ADU-friendly cities in OC. Pre-approved ADU plans available NOW, cutting permit times significantly.
Special Considerations:
Stanton
Standard compliance city with efficient permit process.
Special Considerations:
Tustin
Old Town Tustin has historic district considerations. Otherwise standard process.
Special Considerations:
Westminster
2 stories allowed. Great city for ADUs with straightforward permit process. We've built numerous ADUs and JADUs here including the Cumberland ADU + JADU project.
Special Considerations:
City of Orange
Unique design requirements: ADUs must use at least 2 exterior colors plus 3 architectural elements from approved list.
Special Considerations:
Laguna Beach
Strictest requirements in OC due to hillside terrain and coastal location. All properties require Coastal Development Permit.
Special Considerations:
Rancho Santa Margarita
Interprets state ADU law strictly. However, state law allows 2 ADUs on single-family properties regardless of local limits.
Special Considerations:
Mission Viejo
Master-planned community with strong HOAs. City permits are straightforward but HOA review adds time.
Special Considerations:
Lake Forest
Standard ADU regulations following state law. Efficient building department.
Special Considerations:
California State ADU Law Baseline
California state law sets minimum standards that all cities must follow. Cities can be more permissive but cannot be more restrictive than these baseline requirements:
Cities cannot prevent ADUs of at least 800 sq ft on any residential lot
Rear and side setbacks cannot exceed 4 feet for detached units
Cities must allow ADUs at least 16 feet tall
Cities must approve or deny complete ADU applications within 60 days
Cities cannot require minimum lot sizes for ADU eligibility
No parking required within 1/2 mile of public transit
Effective 2025, cities cannot require owners to live on-site
Building in the Coastal Zone?
Properties in Newport Beach, Huntington Beach, and Laguna Beach often fall within California's Coastal Zone, requiring a Coastal Development Permit in addition to standard building permits. This adds 30-60 days to the permit timeline and may include additional design requirements around height, materials, and view protection.
We have extensive experience navigating Coastal Zone requirements and can determine if your property is affected during our free consultation.
Not Sure What Your City Allows?
Our team knows Orange County ADU regulations inside and out. Get a free property assessment and learn exactly what you can build.