# Snow Load Calculator

Steeper roofs hold less; above 60 degrees the shape coefficient is zero — but not at valleys and parapets.

- Page: https://jianzhujisuan.com/en/snow-load
- Category: Structural Design (https://jianzhujisuan.com/en/c/structural-design)
- Chinese version: https://jianzhujisuan.com/zh/snow-load.md
- Data checked: 2026-10-25

## Quick result

With the default inputs (Ground snow load sk 1.0 kN/m², Roof pitch α 35 °, Exposure coefficient Ce 1.0, Thermal coefficient Ct 1.0, Plan roof area 100 m²): **Roof snow load 0.667 kN/m²**

## Inputs

| Parameter | Type | Default | Unit | Note |
|---|---|---|---|---|
| Ground snow load sk | number | 1.0 | kN/m² |  |
| Roof pitch α | number | 35 | ° |  |
| Exposure coefficient Ce | number | 1.0 | — |  |
| Thermal coefficient Ct | number | 1.0 | — |  |
| Plan roof area | number | 100 | m² |  |

## Formula

- **Shape coefficient**: μ1 = 0.8 (α ≤ 30°)
- ****: μ1 = 0.8(60 − α)/30 (30° < α < 60°)
- ****: μ1 = 0 (α ≥ 60°)
- **Roof snow load**: s = μ1·Ce·Ct·sk
- **Total weight**: S = s × plan area

## Worked example

1.0 kN/m² ground snow, 35° pitch, Ce 1.0, Ct 1.0, 100 m² plan: μ1 0.667, roof load 0.667 kN/m², 66.7 kN total (about 6.8 tonnes), equivalent to roughly 333 mm of settled snow at 200 kg/m³.

## Questions

### How do I calculate roof snow load?

s = mu1 x Ce x Ct x ground snow load. mu1 follows the pitch: 0.8 up to 30 degrees, 0.8(60 − alpha)/30 between 30 and 60, and zero above 60 where snow slides off. Ce is exposure and the EN recommended value is 1.0; the 0.9/1.2 banding is ASCE 7 Table 7.3-1, so do not mix it with the EN default. Ct is thermal and likewise 1.0 by the EN recommendation. Multiply by the plan area, not the sloped area. At 1.0 kN/m² ground snow and 35 degrees, mu1 is 0.667 and the roof carries 0.667 kN/m².

### Does a steep roof mean no snow load?

For the main structure yes, but not locally. A zero coefficient above 60 degrees assumes a clean sloping plane, yet snow slides and piles up: valleys, the low side of stepped roofs, the sheltered face of parapets and around rooftop plant all drift. Local load there can be two to three times the base value and codes require the drift height to be calculated from the roof geometry. Melt-and-refreeze also raises density from about 200 to 400 kg/m³, doubling the weight at exactly the point where it can no longer be cleared — the usual sequence behind light roof collapses in snowy regions.

## Related tools

- [Wind Load Calculator](https://jianzhujisuan.com/en/wind-load): Pressure goes with velocity squared; height enters through the exposure power law.
- [Seismic Base Shear Calculator](https://jianzhujisuan.com/en/seismic-base-shear): Estimate the period, get the coefficient, multiply by seismic weight.
- [Bolt Capacity Calculator](https://jianzhujisuan.com/en/bolt-capacity): Shear or bearing, whichever is lower, governs — above 9 mm plate it is usually shear.
- [Punching Shear Calculator](https://jianzhujisuan.com/en/punching-shear): A column punching through a slab is a race between the perimeter ring and the load.

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