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Snow Load (ASCE 7 Ch. 7)

Flat Roof pf · Sloped Roof ps · Ce · Ct · Is

When to use: Determine design snow loads on a roof per ASCE 7-16 Chapter 7. Start from the mapped ground snow load pg, apply the exposure (Ce), thermal (Ct), and importance (Is) factors to get the flat-roof load pf, then reduce by the slope factor Cs to get the sloped-roof load ps. A minimum snow load pmgoverns for low-slope roofs (θ < 15°).

Site & Roof Parameters
psf
deg
Key Formulas
pf = 0.7·Ce·Ct·Is·pg
ps = Cs·pf
Warm: Cs=1 to 30°, →0 at 70°
Cold: Cs=1 to 37.5°, →0 at 70°
pm = Is·pg (pg≤20) else 20·Is
Sloped Roof Snow Load ps
28.0
psf
Results
Flat Roof Snow pf28.0 psf
Slope Factor Cs1.000 (warm)
Sloped Roof Snow ps28.0 psf
Minimum Snow pm20.0 psf — N/A (θ≥15°)
Exposure Factor Ce1.0
Thermal Factor Ct1.0
Importance Factor Is1.0
Ground Snow pg40 psf
References
ASCE 7-16 §7.3 — flat roof snow
ASCE 7-16 §7.4 — sloped roof Cs
ASCE 7-16 Fig 7.4-1 — slope factor
ASCE 7-16 §7.3.4 — minimum snow