Boston Building Demolition Analysis

Data Processing & Cleaning

1. Strict Data Cleaning: Raw permits were filtered for RAZE only.
   • Prefix Filtering: Excluded non-structural permit types (Plumbing, Electrical, Alteration).
   • Context-Aware Keyword Logic: Applied a "Smart Filter" to remove non-building structures (billboards, pools) and stand-alone auxiliary structures (pure garage/shed demolitions). As a "Rescue Logic" preserved records where garages were demolished alongside main residential or commercial structures.
2. Permit Matching Strategy: Building Polygons were linked to clean Demolition Permits using a Nearest Neighbor Spatial Join with a 5-meter search radius (EPSG:26986).
   Matching Pipeline Stats:

   ● Initial Spatial Matches: 667 (Raw)

   ├─ Exact Matches: 455 (78.6%)
   └─ Buffer Matches (<5m): 124 (21.4%)

   ● Excluded: 70 (Outside Zoning Districts / Invalid Year Built, etc)

   ● Final Analytical Dataset: 509 (Valid)
3. Hierarchical Conflict Resolution: Permits were deduplicated by Address first, then matched to structures. Priority was determined by:
   1. Status Rank: Closed > Open.
   2. Date: Most Recent.
4. Geometry Conversion: Post-matching, building footprints (Polygons) were converted to Centroids (Points) for visualization.
5. Geographic Filtering: Data was filtered to include only structures within defined Boston Zoning Districts.
6. Extra Cleaning: Cleaned buildings without built year, foundation & material type info, GFA =0, and ouliers with lifespans ≥ 500 years were removed.

Calculation Logic

• Lifespan Calculation & Filtering: Demolition Year - Year Built.
  • Positive Lifespan (>0 yrs): Represents a complete, valid building lifecycle. Used in ALL visualizations (Maps, Heatmaps, Age Distributions, Boxplots, etc.) to ensure statistical accuracy.
  • Non-Positive Lifespan (≤0 yrs): Indicates rapid redevelopment (e.g., "Demolished & Replaced" in the same year) or data anomalies. These are strictly excluded from all charts except for:
  • The "Demolitions by Year" stacked chart (shown as a distinct dark grey category).
  • The "RAZE Lifespan Summary" statistics badges.
• Current Buildings Definition: Calculated as the total dataset minus buildings confirmed as demolished.
  • Buildings with a RAZE permit and Positive Lifespan are removed from the "Current Age" charts, as they no longer exist.
  • Buildings with a RAZE permit but Lifespan ≤ 0 are retained. These "Demolished & Replaced" records represent the active structure currently on the parcel.
• Status Inference: Derived from DEMOLITION_STATUS. 'Closed' status is explicitly tracked; all others are classified as Open.