IS 875:1987 Part 4 is the Indian Standard (BIS) for design loads (other than earthquake) for buildings and structures - snow loads. IS 875 Part 4 provides guidelines for calculating design snow loads on roofs and structures. It is primarily used by structural engineers designing buildings in high-altitude or snow-prone regions to ensure structural stability against snow accumulation.
Specifies snow loads to be considered in the design of roofs and other parts of buildings in snowy regions.
Shape coefficient µ for sloped roofs, balanced/unbalanced cases and ground-to-roof snow conversion.
| Reference | Value | Clause |
|---|---|---|
| Code applicability — snow load mandatory above | Hill regions and altitudes per IMD ground snow map | Cl. 1 / 4.1 |
| Ground snow load — design value | From IMD map / 50-yr return period | Cl. 4.1 |
| Snow load on roof — basic relation | s = µ · s₀ (µ = shape coefficient) | Cl. 5.2 |
| Shape coefficient µ — flat / mono-pitch ≤30° | 0.8 | Cl. 5.2 (Fig. 1) |
| Shape coefficient µ — pitched roof 30°–60° | 0.8 · (60 − α)/30 | Cl. 5.2 (Fig. 1) |
| Shape coefficient µ — roof slope ≥ 60° | 0 (snow slides off) | Cl. 5.2 (Fig. 1) |
| Drift / unbalanced load — multi-bay roof valley | Up to 1.6 × balanced load | Cl. 5.3 |
| Min snow density (fresh) | 1.0 kN/m³ (~100 kg/m³) | Cl. 4.1.2 |
| Snow density — settled / compact | 2.0–4.0 kN/m³ | Cl. 4.1.2 |
| Snow + wind combination — partial allowance | Reduced wind pressure on snow-covered roof | Cl. 6 |
| Snow load on canopies / overhangs | Same as adjoining roof + drift | Cl. 5.3.3 |
| Snow on parapets / projections — accumulation | Treated as drifted load | Cl. 5.3.4 |
| Conversion — depth (cm) to load (kN/m²) for fresh snow | ≈ 0.01 kN/m² per cm depth | Cl. 4.1.2 |
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Plain Cement Concrete (PCC) | 24.0 kN/m³ | 24.0 kN/m³ | EN 1991-1-1 |
| Reinforced Cement Concrete (RCC) | 25.0 kN/m³ | 25.0 kN/m³ | EN 1991-1-1 |
| Structural Steel | 78.5 kN/m³ | 78.5 kN/m³ | EN 1991-1-1 |
| Common Burnt Clay Brick Masonry | 18.85 kN/m³ | 16.0 - 20.0 kN/m³ (depending on brick density) | EN 1991-1-1 |
| Cement Plaster | 20.4 kN/m³ | 20.0 kN/m³ (for Cement mortar) | EN 1991-1-1 |
| Cast Iron | 72.08 kN/m³ | 72.5 kN/m³ | EN 1991-1-1 |
| Water (Fresh) | 9.81 kN/m³ | 10.0 kN/m³ | EN 1991-1-1 |
| Glass (Sheet/Plate) | 25.1 kN/m³ | 25.0 kN/m³ | EN 1991-1-1 |