Can we reduce the imposed loads on floors when designing columns in multi-storey buildings?

Yes, Clause 3.2.1 allows progressive reduction of live loads up to a maximum of 50% for columns carrying loads from more than 10 floors.

What is the live load to be considered for staircases in a public building?

It ranges from 4.0 kN/m² to 5.0 kN/m² depending on the specific occupancy class, usually higher than the adjacent floor load to account for emergency egress crowding (Table 1).

How is the imposed load calculated for sloping pitched roofs?

For slopes greater than 10 degrees, the load of 0.75 kN/m² is reduced by 0.02 kN/m² for every degree increase in slope over 10 degrees (Clause 4.1.2).

IS 875 Part 2

: 1987

Design Loads (Other than Earthquake) for Buildings and Structures - Imposed Loads

CurrentEssentialCode of PracticeBIMStructural Engineering · Structural Design and Loading

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This code specifies the imposed (live) loads to be assumed in the structural design of buildings. Engineers use it to determine the minimum uniform distributed loads and concentrated loads for floors, roofs, stairs, and balconies based on the occupancy classification of the structure.

Specifies imposed (live) loads for different occupancies and uses in buildings and structures.

Quick Reference Values

residential floor imposed load2.0 kN/m²

office floor general imposed load3.0 kN/m²

assembly buildings without fixed seating5.0 kN/m²

flat roof with access imposed load1.5 kN/m²

flat roof without access imposed load0.75 kN/m²

max live load reduction columns50% for >10 floors

Key Formulas

Imposed Load on Sloping Roof (>10 degrees) = 0.75 - 0.02 * (alpha - 10) kN/m² — where alpha is roof slope in degrees

Practical Notes

Always differentiate between flat roofs with access (1.5 kN/m²) and flat roofs with access only for maintenance (0.75 kN/m²).

Live load reductions are applicable for designing columns and foundations in multi-storey buildings, but are generally not permitted for the design of the floor slab or beams directly supporting the floor.

For industrial structures or plant rooms, always verify the actual weight of the equipment, as Table 1 only provides minimum generic baseline values.