What is the maximum allowed slenderness ratio for a load-bearing wall?

For walls using cement mortar (not leaner than 1:6) in buildings more than one storey high, the ratio is 27. For taller buildings or different mortars, the limit varies (Clause 5.3.1).

How do you calculate the permissible compressive stress in a masonry wall?

It is calculated as fc = ks * ka * Kp * fb, where fb is the basic stress from Table 9, ks is the stress reduction factor from Table 10, ka is the area reduction factor, and Kp is the shape modification factor from Table 11 (Clause 5.4.1.1).

What is the minimum thickness for a load-bearing wall?

The thickness should not be less than 1/20th of the floor-to-floor height (Clause 6.1.1). For single-storey buildings, thinner walls may be permitted under specific conditions (Clause 6.1.2).

Does this code cover earthquake-resistant design for masonry?

Yes, Clause 10 provides special requirements for buildings in seismic zones, which supplement the main Indian seismic code, IS 1893.

IS 1905

: 1987

Code of Practice for Structural Safety of Buildings - Masonry Buildings

CurrentEssentialCode of PracticeBIMStructural Engineering · Masonry and Bricks

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This is the fundamental code of practice for the structural design and safety of unreinforced masonry buildings. It outlines the requirements for materials like bricks and mortar, details design considerations such as slenderness and stability, and provides methods to calculate permissible stresses. The code also includes special provisions for constructing masonry buildings in seismic zones.

Provides guidelines for the structural design of load-bearing and non-load-bearing masonry walls.

Quick Reference Values

Maximum slenderness ratio for a load-bearing wall (>1 storey)27

Maximum slenderness ratio for a masonry column12

Minimum thickness for single storey load bearing wall1/20th of the storey height

Minimum average compressive strength for common building bricks3.5 N/mm²

Permissible tensile stress (bending) for M1 mortar0.07 N/mm²

Permissible shear stress for M1 mortar0.1 N/mm²

Key Formulas

Permissible Compressive Stress (fc) = ks * ka * Kp * fb — Clause 5.4.1.1 (where ks=Stress Reduction Factor, ka=Area Reduction Factor, Kp=Shape Modification Factor, fb=Basic Compressive Stress)

Practical Notes

This code is for unreinforced masonry; for reinforced masonry design, refer to IS 4326.

Pay close attention to the definition of 'effective height' and 'effective length' of walls, as it is crucial for calculating the slenderness ratio correctly (Clause 5.2).

The permissible compressive stress is a function of multiple factors (basic stress, slenderness, eccentricity, area, shape); ensure all factors from Tables 9, 10, and 11 are considered.