How does SB-9 work in San Diego?

Linda Moore

October 22, 2025 at 03:23 AM

SB-9 (Lot Splits) San Diego, CA

Hi everyone,

I'm a homeowner in San Diego, trying to wrap my head around how SB-9 works with lot splits here in the city. I've read a bit about it, but I could use some expert clarification to make sure I'm on track. My lot is about 8,500 square feet, which I believe meets the minimum requirement for a lot split. However, I'm concerned about how splitting the lot might affect my property taxes and any potential resale value.

I'm working with a modest budget, aiming to keep costs under $200,000 if possible. My main goal is to create additional housing for family members, but I'm also curious about the process for renting out any additional units. Given these constraints, I have a few questions:

1. How does the lot split process work specifically in San Diego? Are there any local zoning laws or regulations I should be aware of that might differ from the general state guidelines?

2. What are the financial implications of a lot split in terms of property taxes? Will my tax rate change significantly if I decide to split the lot and build a new unit?

3. Are there particular design or construction challenges I should anticipate, especially with the city’s permitting process?

I’d really appreciate any insights or experiences from those who've gone through this in San Diego. Thanks in advance for your help!

1 Answer

Lisa Rodriguez

October 20, 2025 at 09:53 AM

Hello and welcome to the forum! It's great to see your interest in taking advantage of SB-9 to maximize your property's potential. Navigating the intricacies of this law, especially in San Diego, can be complex, but I'm here to help break it down for you.

### Understanding SB-9 in San Diego

SB-9, or the California Housing Opportunity and More Efficiency (HOME) Act, allows homeowners to split their lots and build additional housing units with the goal of increasing housing availability. Here’s how this works in San Diego:

1. **Lot Split Process**: In San Diego, your lot must be at least 2,400 square feet to qualify for a lot split under SB-9, which your 8,500-square-foot lot easily meets. The law permits the lot to be split into two roughly equal parcels, with each new parcel no smaller than 1,200 square feet. However, San Diego has its own zoning regulations, so you’ll want to review local zoning maps or consult with the San Diego Planning Department to ensure compliance.

2. **Local Zoning Considerations**: San Diego often requires that any new development maintains neighborhood character, which can affect design and placement of new structures. You will also need to adhere to setbacks, height restrictions, and other design guidelines.

### Financial Implications

3. **Property Taxes**: Splitting your lot and constructing new units can lead to a reassessment of property value, potentially increasing property taxes. However, only the new construction will typically be reassessed at current market value under Proposition 13. The existing home’s tax basis should remain unchanged unless substantial renovations are made. It's advisable to consult with a local property tax advisor to get a more precise estimate based on your specific plans.

4. **Construction Costs**: With a budget of $200,000, you’ll need to plan carefully. Construction costs in San Diego can range from $200 to $300 per square foot, depending on the complexity and finishes. For a modest ADU of approximately 600-800 square feet, your budget might cover the construction costs, especially if you opt for more cost-effective materials and finishes.

### Design and Construction Challenges

5. **Permitting Process**: San Diego’s permitting process is known for being thorough, so factor in time for potential delays. Expect the permitting process to take between 3 to 6 months. Engaging with a local architect or ADU specialist can help streamline this process by ensuring all designs meet city regulations from the start.

6. **Design Considerations**: Consider designs that maximize space efficiency and comply with energy efficiency standards. San Diego requires adherence to Title 24 energy regulations, which could affect design choices, such as window placement and insulation types.

### Additional Considerations

7. **Rental Opportunities**: SB-9 allows homeowners to rent out new units. However, at least one unit on the property must be owner-occupied for a minimum of three years post-approval of the lot split. This could impact your plans if you’re considering renting out both units.

### Practical Steps and Resources

- **Consult Professionals**: Engage a local architect or ADU specialist familiar with San Diego’s regulations. They can provide insights specific to your neighborhood and assist with design and permitting.

- **Explore Financing Options**: Look into local grants or financing options for ADU construction. Programs like CalHFA’s ADU Grant Program may offer assistance.

- **Review Local Ordinances**: Check with the San Diego Development Services Department for the latest local ordinances and guidelines related to SB-9 and ADU construction.

- **Attend Community Workshops**: San Diego often hosts workshops on ADU and SB-9 developments. These can be invaluable for networking and gaining insights from other homeowners who have gone through the process.

### Final Thoughts

Venturing into lot splitting and ADU construction can significantly enhance your property’s value and utility, providing housing for family or rental income. By staying informed and working with local experts, you can navigate the complexities of SB-9 effectively. I hope this information helps you move forward confidently. Feel free to reach out with any more questions, and best of luck with your project!

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Garage Conversion	400-800 sq ft	$80K - $150K	3-6 months	Budget-conscious homeowners
JADU	Up to 500 sq ft	$50K - $100K	2-4 months	Family use, minimal disruption
Attached ADU	600-1,000 sq ft	$120K - $200K	4-8 months	Shared utilities, family proximity
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Permits & Fees: $3K - $15K
Utility Connections: $5K - $20K
Finish Level: $10K - $50K variance
Landscaping: $2K - $10K

Potential ROI

Rental Income: $1,500 - $4,000/month
Property Value Increase: 20-30%
Payback Period: 8-15 years
Tax Benefits: Depreciation allowances
Equity Growth: Long-term appreciation

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Financial Benefits

Rental Income: Generate $18,000-$48,000 annually

Property Value: Increase home value by 20-30%

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Types of ADUs in San Diego, CA

Understanding the different types of Accessory Dwelling Units available in San Diego, CA can help you choose the best option for your property and budget.