Snow Load Rating

Snow load rating quantifies the weight of snow your roof must safely support without failure. Denver building codes specify minimum snow loads based on elevation and location—typically 30 pounds per square foot at lower elevations and up to 50+ pounds per square foot in foothills and mountains. This load combines with dead load (roof weight) to determine required structural capacity. Roof design, rafter or truss sizing, and support spacing all depend on snow load calculations.

Why It Matters in Colorado

Colorado's heavy spring snowstorms can deposit tremendous weight on roofs. Wet, heavy snow weighs 15-20 pounds per cubic foot—a foot of wet snow over 1,000 square feet weighs 15,000-20,000 pounds. Undersized roofs sag, crack drywall, or collapse catastrophically. Denver has experienced numerous roof collapses during heavy snow years. New construction and additions must meet current snow load requirements even if existing structures were built to lower standards. Flat and low-slope roofs are especially vulnerable and require higher safety factors.

Snow Load Considerations

• Ground snow load: Base measurement for location from weather data
• Roof snow load: Accounts for roof slope, exposure, thermal properties
• Drift loads: Additional load from wind-driven snow accumulation
• Unbalanced loads: One side of roof receives more snow than other
• Rain-on-snow: Saturated snow significantly heavier than dry snow
• Structural design: Rafter/truss sizing, support spacing, connection strength