Lot Split (Urban Lot Split)

An urban lot split is the mechanism under California's SB-9 that lets an owner divide a single qualifying single-family lot into two separate lots. Each resulting lot can then host housing — frequently combined with SB-9's allowance of up to two units per lot — so a single parcel that once held one house can, in principle, support substantially more homes. The split is generally constrained so the two new lots are reasonably balanced in size (commonly a minimum split of roughly 60/40).

The appeal of an urban lot split is the same as SB-9 more broadly: where a project meets objective standards, it can move through a ministerial, by-right process rather than discretionary hearings, making the outcome more predictable. Lot splits are a building block of gentle density and overlap with the broader goal of enabling missing middle housing in single-family neighborhoods.

Lot splits carry specific conditions. SB-9 ties them to an owner-occupancy intent affidavit, limits how the resulting lots can be further subdivided, and inherits the law's exclusions — for example, certain historic or hazard-area parcels may not qualify. The minimum lot sizes, frontage, and access requirements that the new lots must satisfy are set partly by the statute and partly by local objective standards.

A lot split is a property-line and entitlement action distinct from simply building an ADU, and it interacts with mapping, title, and financing in ways worth professional review. Because eligibility, split ratios, and local standards vary and can change, this is informational only and not legal advice — verify a specific parcel with the local planning department and consult qualified counsel.