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 (via difference-in-differences deterrent modeling) 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 |
|---|---|---|
| Average unit size | 750 sqft | Conservative for multi-family; actual range 500-1,200 sqft |
| Average lot sizes | Varies by district | RM-1: 1,200 / CMX-2: 2,000 / CMX-3: 8,000 / CMX-5: 25,000 sqft |
| Redevelopment rate | 5% of candidates/year | Consistent with observed rates in transit-proximate Philly neighborhoods |
| Cost cliff threshold | 8 stories | Type V/III wood → Type I steel/concrete (32% cost spike) |
| CMX-5 cliff exemption | Yes | Already building 12+ stories at 1,200%+ FAR; bonus is pure gain |
| Near-term candidates | Vacant + parking + ≤33% utilized | Assessed market value (pre-exemption), OPA category codes, and building descriptions |
| Floor-to-floor height | 10 ft (residential) | Industry standard for story count derivation |
| TOC density bonus | +50% units | Per HOME II §14-513(4)(a) for CMX-1/2/2.5, RM-1 |
| TOC FAR bonus | +30% | Per HOME II §14-513(5)(a)(.2) for CMX-3/4/5, RMX-3 (except /MIN) |
| Mixed-income bonus | +25% units (moderate) | Per §14-702(7) Table 14-702-5; additive, not compounding |
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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