SB 9 Lot Splits, Explained for Investors
What SB 9 actually lets you do
California's SB 9 allows, on many single-family lots:
- A lot split into two parcels, and
- Up to two units on each resulting parcel.
Stack those and a single lot can legally support four units — without a discretionary hearing in most cases.
The catches
SB 9 is powerful but conditional. It generally does not apply when:
- The property is in a historic district or a high fire-hazard zone without mitigation.
- The split would displace existing rent-controlled or recently-occupied tenants.
- The owner won't sign the required owner-occupancy affidavit.
The law removes the entitlement risk. It does not remove the feasibility risk — grade, access, and utilities still decide whether it builds.
Does it pencil?
Run the four-unit scenario against:
- Split and survey costs
- New utility connections for the second parcel
- Rent comps for the unit mix you can actually build
If the pro forma clears your return threshold after those, SB 9 is one of the best value-adds in the state right now.