How Scoring Works
A rigorous analysis of building quality using 11 weighted dimensions and official SF Department of Building Inspection records.
The Algorithm
Weighted composite with anti-clustering
Anti-Clustering Technology
Ensuring unique, differentiated scores
Data Skepticism
Old or large buildings with zero issues are suspicious — either under-inspected or missing data.
100+ units + 0 violations → -5pts
Neighborhood Adjustments
40+ SF neighborhoods have quality adjustments from -2.5 to +2.5 based on area conditions.
Tenderloin → -2.5pts
Building Fingerprint
Deterministic micro-adjustment ensures every building has a unique score — no ties.
→ ±0.5 point adjustment
Top-End Compression
Scores above 92 are compressed to create spread at the top. Max possible is 98.5.
score = 92 + (score-92)*0.7
Result: 4,977+ unique scores across 154K buildings. No clustering at 100. Score range: 18.8 to 94.3.
Core Principles
Time Decay
Recent violations carry more weight. 90 days = 100% weight, 5+ years = 5% weight. Fixed issues fade but never fully disappear.
Open vs Closed
Open violations have 3-8x more impact than closed ones. Current problems matter most.
Per-Unit Normalization
Large buildings naturally have more violations. We normalize by unit count for fair comparison.
Catastrophic Caps
Extreme cases get hard caps: 1000+ violations → max 20. 80+ open violations → max 20.
Max Score Caps
Any violations? Max 97.5. Many violations? Lower caps: 50+ violations → max 85.
SF Climate Factor
SF's mild climate (50-70°F) means heat issues are weighted 1.8× vs 2.5× for NYC/Boston.
San Francisco-Specific Data
Unique factors integrated into scoring
Rent Control Status
Buildings built before June 13, 1979 are subject to SF rent control.
Seismic Retrofit
Soft-story buildings must retrofit — tracked with dedicated scoring dimension.
Eviction History
Owner Move-In (OMI), Ellis Act withdrawals — integrated into eviction risk score.
Fire Inspections
SF Fire Department inspection history contributes to safety score.
SF Rent Control: Buildings constructed before June 13, 1979 are generally subject to San Francisco rent control ordinance. We flag these buildings so renters know their potential protections. Costa-Hawkins exempts single-family homes and condos.
Grade Thresholds
Maximum possible score is 98.5 — no building can reach 100. This ensures meaningful differentiation at the top.
11 Scoring Dimensions
Tap any category to see details
Data Sources
SF vs NYC Scoring
Key differences in methodology
NYC (18 Dimensions)
- • HPD violations with Class A/B/C severity system
- • 311 complaint integration with serial-complainer detection
- • Landlord portfolio analysis across 70K+ landlords
- • Elevator reliability tracking for high-rises
- • Heat violations critical (harsh winters) — 2.5× weight
- • Rent stabilization tracking via DHCR
SF (11 Dimensions)
- • DBI complaints with Notice of Violation data
- • Sophisticated anti-clustering (fingerprints, compression)
- • Seismic retrofit status (unique soft-story tracking)
- • Eviction history (OMI, Ellis Act integrated into score)
- • Heat violations weighted 1.8× (mild climate)
- • Neighborhood quality adjustments (40+ areas)
Why the difference? NYC has 12M+ detailed housing violations with granular classification. SF DBI data is comprehensive but structured differently. Both systems now use sophisticated anti-clustering to ensure score differentiation — no perfect 100 scores, unique fingerprints for tie-breaking, and top-end compression.
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