Code of Practice for
Design Loads (Other than Earthquake)

Overview & Structure

IS 875 provides the criteria for determining the various types of loads that must be considered during the design of buildings and structures. It is divided into five distinct parts: Preamble

• Part 1: Dead Loads — Unit weights of building materials.
• Part 2: Imposed (Live) Loads — Occupancy loads, furniture, movable partitions.
• Part 3: Wind Loads — Pressure based on wind speed zones.
• Part 4: Snow Loads — Based on ground snow load in hilly regions.
• Part 5: Special Loads — Construction loads, crane loads, earthquake loads (reference only).

Part 1: Dead Loads

Dead loads are the static forces due to the weight of the structure itself and permanently attached components. They are calculated using the unit weights provided in Table 1. Cl. 3.1

Common Unit Weights (Approximate)

Finishes:
Tiles/Granite: ~0.5 kN/m² (including adhesive)
Plaster (12mm): ~0.24 kN/m²
Flooring (Mosaic/Ceramic): ~0.15 kN/m²

Part 2: Imposed (Live) Loads

These are variable loads due to occupancy, furniture, and temporary equipment. The values depend on the use category of the building or room. Cl. 4.1

Minimum Imposed Loads on Floors

Reduction of Imposed Loads

For columns, walls, and foundations supporting multiple floors, the total imposed load may be reduced. This accounts for the improbability of full loading on all floors simultaneously. Cl. 4.2

Part 3: Wind Load

This is the most complex part, relying on basic wind speed maps and coefficients for shape, terrain, and height. IS 875 (Part 3)

Design Wind Speed Calculation

Where:

• V_b: Basic Wind Speed (from Map). E.g., Mumbai ≈ 50 m/s, Chennai ≈ 50 m/s, Delhi ≈ 47 m/s.
• k₁: Risk Coefficient (based on design life, e.g., 50 years).
• k₂: Terrain, Height, and Size Factor (depends on surrounding roughness: City vs. Open Country).
• k₃: Topography Factor (effect of hills, ridges, cliffs).
• k₄: Cyclonic Impact Factor (for cyclone-prone coastal areas).

Design Wind Pressure

External & Internal Pressures

Total wind force is calculated as:
F = (C_pe - C_pi) × A × p_d
Where C_pe is external pressure coefficient, C_pi is internal pressure coefficient, and A is area.

Part 4: Snow Load

Applicable only to structures in hilly regions (e.g., Himalayas) where snow accumulation occurs. IS 875 (Part 4)

Snow Load Formula

Ground Snow Load (S₀): Obtained from the map in the code.
Example:
Shimla: ~1.5 kN/m²
Kashmir regions: ~3.0 – 5.0 kN/m²
Delhi/Mumbai: 0 (No snow load)

Shape Coefficient (μ): Depends on roof slope.
Flat roofs (< 10°): μ ≈ 0.8
Sloped roofs (> 60°): μ ≈ 0 (Snow slides off)

Part 5: Special Loads

This part covers loads not covered in other categories: IS 875 (Part 5)

Types of Special Loads

• Construction Loads: Materials stacked during construction, plant equipment, worker loads on formwork.
• Crane Loads: For industrial buildings with overhead traveling cranes (vertical impact, horizontal braking, surge).
• Moving Vehicle Loads: For bridges and car parks (IRC Class AA, A, etc.).
• Liquid/Gas Pressure: For tanks and silos (buoyancy, wave action).
• Temperature Effects: Expansion/contraction forces.
• Earthquake: Referenced here, but detailed in IS 1893.

Crane Load Factors

For gantry girders:

• Vertical Impact: Add 10% to max wheel load.
• Horizontal Surge (Transverse): 5% of max wheel load (electric crane) or 10% (hand operated).
• Longitudinal Surge: 5% of sum of crab weight + lifted load.

Load Combinations

Structures must be designed for the worst-case combination of loads. The primary combinations per IS 456 and IS 800 (aligned with IS 875) are: IS 456 Cl. 36.2

Related Codes

IS 875 is never used in isolation. It works in tandem with: