Single-Family Zoning Reform: An Analysis of SB 1120

Today the Terner Center published a new policy brief exploring Senate Bill 1120, proposed legislation in California that would allow for existing single-family homes to be converted into duplexes and for single-family parcels to be subdivided into two lots.

The analysis reveals that 5,977,061 single-family parcels in California meet minimum lot size and historic district criteria to be eligible for a lot split under bill SB 1120. This total represents approximately 92 percent of all single-family parcels examined in our analysis, and the widespread application of SB 1120 has the potential to result in significant amounts of new housing.

While millions of new parcels may be eligible for a lot split, several factors may impact whether or not new housing could actually get built, such as the size and siting of a parcel’s existing single-family home, and whether or not new housing would require the demolition or alteration of housing that has had rental tenants in the last three years. 

The authors also find that the legislation’s design language could substantially limit the number of new homes that are actually created. In particular, a requirement that a lot split result in two equally sized parcels and limited language on how cities could apply their own design requirements on new lots should be amended in order to better achieve SB 1120’s worthy goals. As the bill makes its way through the Assembly in the coming weeks, now is a good time to make these changes.

The authors conclude that SB 1120 is an important tool to create more opportunities for renters and entry-level homebuyers in single-family neighborhoods and to spur the construction of much-needed new housing in California.

Read the full policy brief on the Terner Center website here.