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.

Episode Overview

This episode launches a critical three-part series on how to correctly calculate the maximum permitable density of housing for any given parcel in California. Sibley argues this is among the most misunderstood aspects of California housing development—and that getting it wrong (which happens at least 95% of the time) means leaving significant housing capacity on the table. Part 1 focuses on parcels where density is expressed in units per acre, walking through the full calculation from general plan designation through density bonus law and multifamily ADU provisions.

Host & Guest

Host: Sibley Simon — Founder, Workbench (Integrated Real Estate Development, Santa Cruz, CA)

Guest: Chris Hudon — Director of Development, Workbench (25 years of multifamily development experience in Colorado and Utah)

Why This Guest

Sibley specifically brought Chris on for Part 1 because Chris is an experienced multifamily developer—but not in California. His background in Colorado and Utah, where developers rely on local zoning, site constraints, and informal planning department consultations, makes him the perfect stand-in for what most developers do when entering the California market. Chris's fresh perspective highlights just how different—and counterintuitive—California's density calculation system is compared to the rest of the country.

What is SB 79?

SB 79 is California's landmark transit-oriented housing upzoning bill, passed in 2025 after eight years of legislative attempts. The law requires certain jurisdictions to allow mid-rise apartment buildings (typically 4-7 stories) near major transit stops.

Guest: Aaron Eckhouse

Regional Planning Program Director, California YIMBY

Aaron has spent eight years working on transit-oriented upzoning legislation in California, from SB 27 and SB 50 to the successful passage of SB 79 in 2025.

Host: Sibley Simon

Principal and Impact Development Executive, Workbench

Host of The Infill Insiders

Key Takeaways

1. Historic Achievement: First successful statewide transit-oriented upzoning after 8 years of attempts
2. Narrow Victory: Passed by one vote on multiple occasions—every vote counted
3. Political Reality: Bill was trimmed significantly to secure passage; expansion may come if it proves successful
4. Implementation Timeline: Most provisions take effect July 1, 2026; some penalties delayed until January 2027
5. City Options: Jurisdictions can create their own qualifying plans or delay implementation for certain areas
6. Practical Guidance: Developers should focus on sites that can be built lot-line to lot-line to maximize density bonus law benefits
7. Future Cleanup: Expect cleanup legislation to address measurement ambiguities and other technical issues

Key Provisions

• Height Limits: Up to 75 feet in Tier 1 zones (highest), with lower tiers at 65 feet and 55 feet
• Density: Up to 120 units per acre in top tier zones
• FAR (Floor Area Ratio): Up to 3.5 residential FAR in top tier zones
• Distance: Applies within quarter-mile and half-mile radii of qualifying transit stops
• Effective Date: July 1, 2026 for most qualifying jurisdictions

Where It Applies

• Qualifying Counties: Must have 15+ Tier 1 or Tier 2 rail transit stops
• Urban Transit Counties: Sacramento, Alameda, San Francisco, San Mateo, Santa Clara, Los Angeles, Orange (soon), San Diego
• Transit Types: Heavy rail, light rail, commuter rail, and qualifying Bus Rapid Transit (BRT) lines
• City Size Threshold: Half-mile radius provisions only apply in cities over 35,000 population

What It Doesn't Cover

• Most of California (limited to major transit counties)
• Contra Costa County (specifically excluded)
• Santa Cruz County and other non-qualifying counties
• Areas more than a mile walking distance from transit
• Very high fire hazard severity zones (can be excluded)
• Sites with existing affordable or rent-controlled housing (7-year lookback)

Impact Assessment

Potential Benefits

1. Significant Zone Capacity: Creates substantial new housing capacity near transit
2. Climate Goals: Reduces car dependency by enabling housing where people can use transit
3. Transit Ridership: More residents near transit supports system viability
4. Housing Production: Enables "workhorse" mid-rise multifamily in high-demand areas

Challenges & Limitations

1. Geographic Restrictions: Only applies in a small fraction of California
2. Density Bonus Interaction: Complex calculations may limit project feasibility
3. Inclusionary Requirements: 10% very low income requirement plus local inclusionary ordinances
4. Distance Measurement Ambiguity: "Closest edge" language may create disputes
5. Anti-Displacement Provisions: 7-year lookback may block beneficial redevelopment