Building an ADU is one of the smartest ways to add living space and value to your property. But every project needs to follow San Diego’s ADU regulations—covering size, height, setbacks, parking, and permits. Missing even one rule can cause costly delays or force you back to the drawing board. That’s why understanding the basics before you start is essential.
ADU Sizes in San Diego 2025
- Maximum size: Up to 1,200 sq. ft. for detached or attached ADUs.
- Minimum size: About 150 sq. ft., but it must still meet California’s habitability standards like ceiling height, light, and ventilation.
- Stories & height: You can generally build up to two stories, but once you go higher than 16 feet, more setback requirements kick in.
This means you can create anything from a compact studio to a generous two-bedroom ADU, depending on your lot.
Setback Requirements
Setbacks determine how close your ADU can be to property lines. Here’s the quick version:
- Side & rear yard setbacks:
- For ADUs 16 ft or under, zero-foot setbacks are often allowed.
- For ADUs over 16 ft tall, a minimum 4 ft setback is required.
- Front yard setbacks: You typically must respect the front setback of your zone, though ADUs under 800 sq. ft. may qualify for some exceptions.
- Corner lots / street side: Usually 4 ft, or the base zone’s rule, whichever is less.
If you’re in a fire hazard zone, extra setbacks and fire-rated materials may apply. We’ve seen this come up often in hillside neighborhoods.
Parking Rules for ADUs in San Diego
Here’s the good news: in most cases, no parking is required for ADUs in San Diego.
However, there are exceptions:
- Properties in the Coastal Zone (especially the Beach Impact Area) may still need one parking space.
- Bonus or affordable ADUs outside Transit Priority Areas may also trigger parking requirements.
We always confirm these details early so there are no last-minute surprises.
How Many ADUs Can You Build in San Diego’s Properties?
- Single-family lots: Usually 1 detached ADU + 1 JADU (Junior ADU).
- Multifamily lots: In many cases, you can build more ADUs or convert existing space into multiple units.
San Diego is expanding its ADU allowances, but the exact number depends on zoning and lot size.
ADU Ownership & Rental Rules in San Diego
- Owner occupancy: For standard ADUs, it’s generally not required.
- JADUs: Historically required owner occupancy, but 2025 updates allow more flexibility.
- Separate sale: Thanks to recent reforms, some ADUs can now be condo-converted and sold separately, adding investment potential.
The Typical ADU Timeline in San Diego
From start to finish, here’s what we see on most projects:
- Site analysis & consultation: 1–2 weeks
- Design & plans: 4–8 weeks
- Permit review: 4–10+ weeks
- Pre-construction setup: 1–3 weeks
- Construction & inspections: 8–20+ weeks
Overall, most ADUs take 3–8 months from idea to move-in, depending on complexity and city review times.
Extra Tips from Our Experience [SHEINER CONSTRUCTION]
- Garage conversions: Often allowed to keep existing setbacks.
- Impact fees: ADUs under 750 sq. ft. are typically exempt from many city fees.
- Transit areas & bonus programs: Building near transit can reduce parking requirements and open affordable housing incentives.
- Policy shifts: In 2025, San Diego is rolling back some backyard ADU allowances in dense neighborhoods, so check your parcel before committing.
Conclusion: Build Smart
San Diego’s 2025 ADU rules give homeowners incredible opportunities to add space, rental income, and value—but the details matter. From setbacks and parking to timelines and fees, the difference between a smooth project and a stalled one comes down to knowing the rules.
At Sheiner Construction, we don’t just build ADUs—we guide you through the entire process. From checking your zoning to drawing plans, pulling permits, and passing inspections, we handle the headaches so you can focus on the excitement of adding a new living space to your home.
If you’re considering an ADU in 2025, let’s talk. We’ll help you design a unit that fits your property, your budget, and your vision—while staying 100% compliant with San Diego’s evolving rules.
