Calculating Permitable Density Part 2 of 3: Density Bonus Law and Form Based Zoning

In this second installment of the density calculation series, Sibley Simon walks Serena Collins through form-based density—the method used when local zoning does not specify a units-per-acre standard. The episode explains how developers use Floor Area Ratio (FAR) as the controlling density measure, how to conduct a base density study to convert FAR into a unit count, and how density bonus law then multiplies that count. The discussion also covers strategic use of multifamily ADUs, the role of the Housing Accountability Act in resolving code conflicts, and the critical distinction between entitlement-stage and building-permit-stage decisions.

Guest

Serena Collins – Project Manager, Workbench / New Way Homes

Serena has been with Workbench for 5 years managing project development and capital raising. She specializes in brownfield site cleanup and redevelopment funding and grant writing at both the state and federal level.

Here’s what you’ll learn:

• What form-based density means and when it applies (hint: most commercial corridor and mixed-use zones)
• How Floor Area Ratio (FAR) becomes your controlling density measure
• The base density study process — and why it requires an architect to design a building you’ll never construct
• Why your base density study doesn’t need to be financially feasible (and how to use that to your advantage)
• How to resolve conflicts between your general plan and zoning code using the Housing Accountability Act
• The three density layers: base density + stacked bonuses + multifamily ADU conversions
• A real example of how 5-story zoning can yield an 18-story building

Why This Matters:

• For developers and landowners: The base density study is the single most important step in maximizing your site’s housing capacity under California law. Getting it right — or getting it wrong — can mean dozens of units of difference on the same parcel.
• For housing policymakers: Understanding how form-based density translates into actual unit counts is essential for evaluating whether your zoning code is achieving its housing production goals.
• For multifamily investors: The density math is the feasibility math. Knowing how base density, bonus density, and ADU layering interact tells you whether a site pencils — before you ever write a check.

Coming next: Part 3 covers the alternative density pathways — additional state law methods that may yield even more units, with different tradeoffs. That episode will complete the full 2026 picture of how to calculate the density you have the right to build on any California site.