Two different laws, two different goals
SB 9 (effective 2022) lets single-family homeowners split their lot and build a duplex on each resulting parcel. ADU law lets you add up to two units (ADU + JADU) to an existing single-family property without splitting the lot.
Both are powerful — but they answer different questions.
Choose ADU when you want to:
- Add rental income while keeping one property title
- Avoid lot-split surveying, easements, and HOA disputes
- Move quickly (4–9 months total)
- Spend less upfront (a property-specific written estimate for typical detached ADU)
Choose SB 9 when you want to:
- Eventually sell off the new lot separately
- Build up to 4 total units on what was one lot
- Maximize total density on a large lot
- Are willing to invest in survey work and slower permitting
Costs side by side
| Path | Typical Cost | Timeline | Units Added |
|---|---|---|---|
| ADU + JADU | Property-specific written estimate | 6–9 months | 2 |
| SB 9 lot split + 2 duplexes | Property-specific written estimate | 12–18+ months | 3–4 |
Can you stack them?
In some cases yes — you can build an ADU first and pursue SB 9 later, though it becomes complex. Consult an attorney before planning a combined strategy.
Get a real assessment
Book a free site evaluation and we will tell you whether SB 9 or ADU (or both) makes sense for your property.
Frequently Asked Questions
Can I do both SB 9 and an ADU?
Yes in some cities, but it is complex and many cities have not fully harmonized the two ordinances. Legal review required.
Which is faster: SB 9 or ADU?
ADU is dramatically faster. SB 9 requires lot splits, surveys, and often longer plan checks.
Does SB 9 cost more than ADU?
Yes — significantly. SB 9 typically requires a property-specific written estimate in survey, legal, and infrastructure costs before construction.
Are SB 9 lots smaller than the original?
Yes — the new lots are typically half the original parcel size.
Do HOAs block SB 9?
HOAs cannot block SB 9 in eligible single-family zones, the same as ADUs.
Related Vision ADU Resources
- Detached vs Attached ADU: Which Is Right for Your Property? (California 2026)
- JADU vs ADU in California: Cost, Rules & When to Choose Each (2026)
- Garage Conversion ADU Permits in California (2026 Step-by-Step)
- ADU Setback Requirements in California (2026 State Minimums + City Rules)
- ADU Contractor in Pasadena
- ADU Contractor in Santa Monica
- Los Angeles County ADU Builder
- Orange County ADU Builder
- Inland Empire ADU Builder
- 2026 ADU Cost Calculator
- All Vision ADU Service Areas