❄️ Snow Load Calculator
Calculate roof snow load for structural design
Typical: 20-50 psf for most areas (check local codes)
Enter 0 for flat roofs
How to Use This Calculator
Enter Ground Snow Load
Input the ground snow load in psf (pounds per square foot) for your area. Check local building codes or use 20-50 psf as typical values for most areas.
Enter Roof Pitch
Input the roof pitch in inches per 12 inches of run. For flat roofs, enter 0. Higher pitches reduce snow load.
Select Building Factors
Choose roof type (heated/unheated/cold), terrain type (sheltered/normal/exposed), and importance factor (low/normal/high).
Calculate and Review
Click "Calculate Snow Load" to see roof snow load in psf and kPa. Always consult local building codes for official requirements.
Formula
Roof Snow Load = 0.7 × Ce × Ct × Is × Pg × Cs
Where: Ce = Exposure Factor, Ct = Thermal Factor
Is = Importance Factor, Pg = Ground Snow Load
Cs = Slope Factor (reduces for steeper roofs)
Example: 30 psf ground load, 6/12 pitch, unheated, normal terrain
Step 1: Ce = 0.9 (normal), Ct = 1.1 (unheated), Is = 1.0 (normal)
Step 2: Pitch angle = arctan(6/12) = 26.6°
Step 3: Cs factor = ~0.67 (reduction for 26.6° pitch)
Step 4: Roof load = 0.7 × 0.9 × 1.1 × 1.0 × 30 × 0.67 = 13.9 psf
About Snow Load Calculator
The Snow Load Calculator is an essential tool for structural engineers, architects, contractors, and builders who need to calculate roof snow loads for structural design. This calculator eliminates guesswork by providing snow load estimates based on ground snow load, roof pitch, and building factors, helping you design structures that can safely support snow loads.
When to Use This Calculator
- Structural Design: Calculate snow loads for roof framing and structural design
- Code Compliance: Verify snow loads meet building code requirements
- Roof Framing: Size rafters, trusses, and beams for snow loads
- Building Planning: Plan roof structures to support expected snow loads
- Renovation Projects: Assess existing roofs for snow load capacity
Why Use Our Calculator?
- ✅ Accurate Estimates: Snow load estimates based on simplified ASCE 7 formulas
- ✅ Multiple Factors: Accounts for ground snow load, pitch, roof type, terrain, and importance
- ✅ Pitch Reduction: Automatically reduces snow load for steeper roofs
- ✅ Time Savings: Instant calculations eliminate manual math
- ✅ Easy to Use: Simple input fields for all relevant factors
Understanding Snow Load
Ground Snow Load: Ground snow load (Pg) is the design snow load at ground level for your area, specified in pounds per square foot (psf). It's based on historical snowfall data and varies by location. Check local building codes for your area's ground snow load.
Roof Snow Load: Roof snow load is typically less than ground snow load due to factors like roof pitch, exposure, and thermal conditions. Steeper roofs shed more snow, reducing the load. The calculator accounts for these factors.
Building Factors: Thermal factors (heated vs unheated), exposure factors (sheltered vs exposed terrain), and importance factors (low, normal, high) all affect snow load calculations. Unheated buildings accumulate more snow, while sheltered areas have different drift patterns.
Important Notes
- Local Codes Apply: Snow load requirements vary by local building codes and ASCE 7 standards
- Consult Engineers: For structural design, always consult a structural engineer
- These Are Estimates: The calculator provides estimates based on simplified formulas—actual calculations are more complex
- Multiple Factors: Actual snow load depends on drift, sliding, local conditions, and many other factors
- Professional Review: For critical structures, consult a structural engineer for official calculations
Frequently Asked Questions
What is ground snow load?
Ground snow load (Pg) is the design snow load at ground level for your area, specified in pounds per square foot (psf). It's based on historical snowfall data and varies by location. Typical values are 20-50 psf for most areas, but can be much higher in mountain regions.
How do I find my ground snow load?
Check your local building codes, ASCE 7 snow load maps, or contact your local building department. Ground snow load varies significantly by location—coastal areas typically have 20-30 psf, while mountain regions may have 100+ psf.
How does roof pitch affect snow load?
Steeper roofs shed more snow, reducing snow load. Roofs with pitches above 70° typically have minimal snow load. The calculator automatically reduces snow load for steeper pitches based on standard formulas.
Why does unheated roof have higher snow load?
Unheated roofs (like unheated garages or sheds) accumulate more snow because there's no heat to melt it. Heated roofs have heat loss that melts some snow, reducing accumulation. The calculator accounts for this with thermal factors.
Are these calculations accurate for all buildings?
These calculations provide estimates based on simplified formulas. Actual snow load calculations are more complex and consider drift, sliding, local conditions, wind patterns, and many other factors. Always consult local building codes and a structural engineer for official requirements.