Understanding Roof Loads
Total Load = Dead Load + Live Load + Snow Load
Dead Load = Material + Sheathing + Framing + Insulation
Live Load = 20 PSF (standard code minimum)
Snow Load = Ground Snow × Pitch Factor × Exposure Factor
Load Types
- Dead Load: The permanent weight of the roof structure itself — framing, sheathing, underlayment, and roofing material. Ranges from 7-25 PSF.
- Live Load: Temporary loads from workers, equipment, and maintenance. Code minimum is 20 PSF for most residential roofs.
- Snow Load: Weight of accumulated snow. Varies dramatically by region (0-90+ PSF). Steeper pitches shed snow faster.