Calculate a simplified roof snow load estimate based on ASCE 7-style inputs. Determines structural requirements for snow country buildings.
Last updated: March 2026
ft²
psf
rise:12
*Simplified estimate based on ASCE 7-style inputs: pf = 0.7×Ce×Ct×Is×pg. Omitted factors include drifting, unbalanced loading, and roof-geometry adjustments. Always consult local building codes.
Snow load is the weight of accumulated snow on a roof or structure, measured in pounds per square foot (psf). It's a critical structural design parameter in regions that experience winter snow, as excessive snow accumulation can cause roof collapse or structural failure.
The ASCE 7 Standard specifies how to calculate design snow loads based on geographic location (ground snow load), roof characteristics (slope, exposure, thermal properties), and structural importance. Buildings in high-snow regions require stronger roof framing to safely carry peak snow loads.
Factors affecting snow load include roof slope (steeper roofs shed snow), roof exposure to wind, insulation level (heated vs. unheated), and local climate data. Professional engineers use these calculations to ensure building safety during extreme weather events.
Calculate snow load for a residential home in Minnesota:
The roof must be designed to safely support 49 tons of snow.
Ground snow load (pg) is the maximum snow depth expected on flat ground in your region, converted to weight per square foot. It's determined from historical climate data and published in ASCE 7 and local building codes.
Steep roofs shed snow more easily due to gravity and wind action. Roofs steeper than ~70° usually shed snow entirely (Cs = 0). Gentler slopes retain more snow, requiring stronger framing.
Exposure describes the roof's wind exposure. Exposed, windswept roofs shed snow (Ce = 0.8). Sheltered roofs surrounded by trees retain snow (Ce = 1.2). Normal exposure uses Ce = 1.0.
Heat loss through the roof can melt the bottom layer of snow (lower bound or ice dam formation). The thermal factor (Ct) accounts for this. Most residential buildings use Ct = 1.0.
Yes. Snow load design affects structural safety and must comply with local building codes. Always consult a licensed structural engineer for actual building design and building permit requirements.
This is an educational tool showing ASCE 7 principles. Professional engineering design requires verification against current codes, site-specific data, and approval by local authorities having jurisdiction.
Check ASCE 7 Figure 7-1 (snow load maps), your local building department, or the Automated Buildings' Snow Load Analyzer. Many regions have updated climate-based values.
Complex roof geometries (domes, arches) need specialized analysis. ASCE 7 Section 7.6+ provides methods for non-uniform snow distribution. Professional design is essential.
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