Data & Methodology
How we built this analysis. Every number on this site is traceable to a data source, a zoning code section, or a published study. Download the workbook to check our math.
The buildability estimates on this site and in the BPN dashboard are produced by our zoning rules engine. Base district calculations, CMX-1 adjacency rules, building footprint data, utilization ratios, and the /MIN overlay (reported as gated capacity, not as a modelled unit loss) are all integrated. Results may still be imprecise for parcels with multiple overlapping overlays (/NE, /NCO, etc.), other adjacency-dependent districts (RM-2, SP-*), or nonconforming structures. Phase 2 will add full overlay stacking and the remaining adjacency rules.
Data Sources
Philadelphia Parcel Data
545,796 parcels with zoning classifications, property categories, building descriptions, assessed market values (pre-exemption), and transit proximity flags (500 ft, 1,320 ft, 2,640 ft buffers around MFL and frequent bus stations).
Building Footprints
Actual lot areas and building footprints joined to parcels, replacing average lot size estimates. Used for building envelope calculations and utilization ratios.
CMX-1 Adjacency
10,234 adjacency relationships for 4,894 CMX-1 parcels. 3,712 high-confidence parcels (71%) with clear non-CMX-1 abutting neighbor per §14-203(1). Most restrictive adjacent district standards applied.
Zoning Code Standards
Dimensional standards tables 14-701-1 through 14-701-4. District-level max height, FAR, lot coverage, setbacks, and density rules for all RSA, RSD, RTA, RM, CMX, and RMX districts.
Construction Cost Thresholds
Philadelphia-specific data: $166/sqft (wood frame, 1-3 stories), $171/sqft (wood frame, 4-7 stories), $216/sqft (steel/concrete, 8+ stories). 32% cost spike at the 7→8 story threshold.
Transit Station Data
Housing units permitted within station catchment areas, aggregated by station. Demonstrates existing developer interest and market demand near transit.
Parker TOC Bills
13 MFL stations, 1,320 ft radius, eligible zoning categories, density and FAR bonus structures, parking reductions, and excluded zones.
The Zoning Rules Engine
BPN built a zoning rules engine that implements the Philadelphia Zoning Code dimensional standards for computing maximum building capacity per parcel. The engine processes each parcel through these steps:
Key Assumptions
| Assumption | Value | Rationale |
|---|---|---|
| Station areas | 1,320 ft (¼ mile) from each entrance | §14-513(3)(b)(.1). All 98 Broad Street Line, Market-Frankford Line, and Regional Rail stations in the city; trolley stops not included |
| Underused lot | Building uses under about ⅓ of allowed capacity and is under 20,000 sq ft | Same definition as BPN's Center City District and single-stair analyses; parks, active places of worship, and civic buildings excluded |
| What counts | Underused lots with /TOC-eligible zoning only | Built-out lots are not counted toward either bonus; each lot is counted once where station areas overlap |
| TOC unit bonus | +50% units | §14-513(4)(a) for CMX-1/2/2.5, RM-1 |
| TOC FAR bonus | +30% | §14-513(5)(a)(.2) for CMX-3/4/5, RMX-3; does not apply in /MIN |
| /MIN | Reported as gated capacity | Homes today's zoning allows on underused lots inside /MIN; the /TOC unit bonus there is not counted. No deterrent is modeled |
| Average unit size | 750 sq ft | Converts floor-area bonus square footage to homes |
Limitations
Open for Review
BPN’s zoning rules engine source code and all 13 JSON rule files (covering the full Philadelphia Zoning Code Title 14) are available for review. We welcome corrections, improvements, and questions. Contact us at jon@buildphillynow.org.
Check Our Math
Download the workbook. Review the assumptions. If we got something wrong, tell us — we'll fix it.
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