Formulas from the Slovenian national annex
| Zone | Characteristic snow load on the ground sk [kN/m²] |
|---|---|
| A1 | sk = 0.651 · [1 + (A/728)²], but at least 1.2 kN/m² |
| A2 | sk = 1.293 · [1 + (A/728)²] |
| A3 | sk = 1.935 · [1 + (A/728)²] |
| A4 | sk = 2.577 · [1 + (A/728)²] |
| M1 | sk = 0.289 · [1 + (A/452)²] |
A is the altitude in metres. In the Alpine region the annex requires at least 1.2 kN/m², which only matters in zone A1. Because the altitude is squared, the values grow very quickly in high mountains – for buildings high up (mountain huts, cable car stations) check the annex and local snow data carefully.
Snow load on the roof: s = μ₁ · Cₑ · Cₜ · sk. For a monopitch or duopitch roof the shape coefficient is μ₁ = 0.8 for pitches up to 30°, decreases linearly to 0 at 60° (μ₁ = 0.8 · (60 − α) / 30), and is 0 above 60° – if snow can slide off freely. Snow guards or parapets keep μ₁ at 0.8 or more.
Not included: drifting at parapets and steps, snow overhanging the eaves, unbalanced load on duopitch roofs (μ₁ on one side and 0.5·μ₁ on the other), and exceptional snow. The national annex uses Cesl = 2.0 for exceptional snow only above 1500 m.
Source: SIST EN 1991-1-3:2004/A101:2008, the Slovenian national annex to Eurocode 1, part 1-3. Check that you use the valid edition.
For learning and quick checks only. Real structures must be designed by a licensed engineer according to the valid standards.