Enter Snow Load Inputs
Plotly Graph
Example Data Table
| Project | Pg (psf) | Ce | Ct | Is | Cs | Drift | Roof Area (sq ft) |
|---|---|---|---|---|---|---|---|
| Retail Canopy | 25 | 1.00 | 1.00 | 1.00 | 1.00 | 1.10 | 1,200 |
| School Wing | 35 | 1.00 | 1.10 | 1.10 | 0.90 | 1.15 | 4,500 |
| Storage Shed | 20 | 0.95 | 1.00 | 1.00 | 1.00 | 1.00 | 900 |
Formula Used
Flat roof snow load: Pf = 0.7 × Ce × Ct × Is × Pg
Balanced roof snow load: Ps = Pf × Cs
Design snow load: Pd = (Ps × drift factor) + surcharge
Actual snow load from field measurement: Actual psf = depth in feet × snow density in pcf
Total roof force: total force = load in psf × roof area in square feet
This layout lets you compare code-style design input values with field-observed snow buildup on the roof surface.
How to Use This Calculator
- Enter the project name, ground snow load, and roof area.
- Add the selected exposure, thermal, importance, and slope factors.
- Include a drift factor or any extra surcharge when required.
- Enter measured roof snow depth and estimated snow density.
- Press calculate to view design load, actual load, reserve, and total force.
- Review the graph and export the result as CSV or PDF.
FAQs
1. What does this snow load calculator estimate?
It estimates flat roof snow load, balanced roof load, drift-adjusted design load, actual field snow load, total roof force, reserve load, and utilization percentage.
2. What is ground snow load?
Ground snow load is the site snow weight used as a starting design input. It comes from the governing code map, local authority, or project engineer.
3. Why are exposure, thermal, and importance factors included?
These factors adjust the base snow load for building conditions, environment, and risk level. They help convert raw ground snow information into a roof design load.
4. Why compare design load with actual measured snow?
Measured snow depth and density show what may be sitting on the roof today. Comparing them with design values helps with monitoring and snow removal planning.
5. What does the drift factor do?
The drift factor increases the balanced roof load to reflect localized buildup near higher roofs, parapets, walls, or obstructions where drifting may occur.
6. Can I use this for sloped roofs?
Yes, when you enter an appropriate slope factor. The tool lets you reduce or maintain the flat roof load depending on the roof configuration.
7. What units does the calculator use?
Loads are in pounds per square foot, density is pounds per cubic foot, depth is inches, roof area is square feet, and total force is pounds.
8. Is this enough for final structural approval?
No. It is a planning and screening tool. Final design, checking, and roof safety decisions should be verified under the governing code by a licensed engineer.