Convert snowfall depth to water equivalent and calculate weight — useful for roof loading and clearing.
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How This Works
Snow water equivalent (SWE) = snow depth × (snow density ÷ water density). Fresh light snow has density ~100 kg/m³ (very fluffy, 10:1 snow-to-water ratio). Settled snow ~200 kg/m³. Wet snow (near 0°C) ~350 kg/m³. Compacted/icy snow ~500 kg/m³. Roof load in kN/m² = weight in kg/m² × 0.0098.
UK Building Regulations (BS EN 1991-1-3) set snow load requirements at 0.6 kN/m² for most of England and Wales (~60 kg/m²), rising to 1.0 kN/m² in northern Scotland. This equates to roughly 30cm of fresh snow or 17cm of wet snow. Modern well-maintained roofs typically handle UK snowfall safely. Risk factors: older roofs with degraded structure, flat or low-pitch roofs where snow accumulates, and heavy wet snow (March snowfall is often wetter and heavier than winter snow).