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IS 1905:1987 is the Indian Standard (BIS) for structural safety of buildings - masonry buildings. 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 — IS 1905:1987 Structural Masonry
Code of practice for structural use of unreinforced masonry. Permissible stresses, slenderness, mortar grades.
✓ Verified 2026-04-28
Reference
Value
Clause
Mortar grade H1 — cement:lime:sand
1 : 0–¼ : 3 (compressive 10 N/mm²)
Cl. 4.2.1 (Table 1)
Mortar grade H2
1 : ½ : 4½ (compressive 7.5 N/mm²)
Cl. 4.2.1 (Table 1)
Mortar grade M1
1 : 1 : 6 (compressive 5 N/mm²)
Cl. 4.2.1 (Table 1)
Mortar grade M2
1 : 2 : 9 (compressive 3 N/mm²)
Cl. 4.2.1 (Table 1)
Mortar grade L1
0 : 1 : 3 (compressive 1.5 N/mm²)
Cl. 4.2.1 (Table 1)
Permissible stress — Class A brick (10 MPa) + H2 mortar
0.7 N/mm²
Cl. 5.4.1 (Table 8)
Permissible stress — Class A brick + M1 mortar
0.55 N/mm²
Cl. 5.4.1 (Table 8)
Permissible stress — Class B brick (7.5 MPa) + M1
0.41 N/mm²
Cl. 5.4.1 (Table 8)
Permissible tensile stress — flexure
0.07 N/mm² (parallel to bed joint)
Cl. 5.4.2
Permissible shear stress — H2 mortar
0.10 N/mm²
Cl. 5.4.3
Slenderness ratio — maximum (load-bearing)
27
Cl. 5.4.1 (Table 9)
Effective height — wall pinned top + bottom
h
Cl. 4.5.1
Effective height — wall fixed top + bottom
0.75 h
Cl. 4.5.1
Effective thickness — solid wall
= actual wall thickness
Cl. 4.5.2
Stress reduction factor (slenderness 12)
0.84
Cl. 5.4.1.1 (Table 9)
Stress reduction factor (slenderness 18)
0.62
Cl. 5.4.1.1 (Table 9)
Stress reduction factor (slenderness 27)
0.30
Cl. 5.4.1.1 (Table 9)
Eccentricity factor — e/t ≤ 1/6
1.0
Cl. 5.4.1.1 (Table 10)
Eccentricity factor — e/t = 1/3
0.45
Cl. 5.4.1.1 (Table 10)
Cement consumption — 230 mm wall (M1 mortar)
≈ 0.034 m³/m² of wall
(typical)
Bricks per m³ — modular brick
≈ 500
(typical)
⚠ Reaffirmed. The Indian working-stress code for masonry. Cross-referenced with IS 4326 (seismic detailing) and IS 13920 / IS 1893 for earthquake context.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
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.
Consolidated list per BIS. For the text of each amendment, refer to the BIS portal link above.
masonrybricksconcrete blocksmortar
International Equivalents
Similar International Standards
EN 1996-1-1:2005CEN (European Committee for Standardization)
HighCurrent
Eurocode 6: Design of masonry structures - Part 1-1: General rules for reinforced and unreinforced masonry structures
Covers general rules for the structural design of unreinforced and reinforced masonry buildings using a limit state design approach.
TMS 402/602-22The Masonry Society (TMS) (US)
HighCurrent
Building Code Requirements and Specification for Masonry Structures
Provides comprehensive design and construction requirements for masonry structures in the United States, including allowable stress and strength design.
Code of practice for the use of masonry - Part 1: Structural use of unreinforced masonry
Provided allowable stress design guidance for unreinforced masonry and was historically influential, sharing a similar design philosophy to IS 1905.
AS 3700:2018Standards Australia (AU)
HighCurrent
Masonry structures
Specifies requirements for the design and construction of unreinforced, reinforced, and prestressed masonry using a limit state design approach.
Key Differences
≠IS 1905 is based on a Working Stress Design (WSD) philosophy, using permissible stresses and a single global factor of safety. In contrast, modern equivalents like Eurocode 6 (EN 1996) and TMS 402 use a Limit State Design (LSD) or Strength Design approach, which employs partial safety factors for loads and material strengths.
≠In IS 1905, the basic compressive strength of masonry is determined from a lookup table (Table 8) based on unit strength and mortar type. Eurocode 6 uses an empirical formula (e.g., fk = K * fb^α * fm^β) to calculate the characteristic compressive strength, allowing for a more continuous and flexible range of material combinations.
≠The approach to slenderness is different. IS 1905 specifies a maximum slenderness ratio (e.g., 27 for a single-storey wall) and applies a 'stress reduction factor' from a table. Eurocode 6 does not set a hard limit but calculates a 'capacity reduction factor' (Φ) based on eccentricity and slenderness, which can heavily penalize very slender walls.
≠Seismic design provisions in IS 1905 are minimal. Detailed seismic design for masonry in India is referred to other codes (like IS 1893). In contrast, Eurocode 6 is designed to be used with Eurocode 8 (Design for earthquake resistance), which provides integrated and comprehensive seismic rules for masonry structures.
Key Similarities
≈Both IS 1905 and its international equivalents base the design compressive strength of a masonry element on the combined properties of the masonry units (bricks/blocks) and the mortar.
≈All standards recognize the low tensile and flexural strength of unreinforced masonry and provide specific permissible values or calculation methods for bending perpendicular and parallel to the bed joints.
≈Both the Indian and international codes require designers to account for the effects of slenderness and eccentricity of loading, applying reduction factors to the wall's load-carrying capacity to prevent buckling failure.
≈The calculation of shear strength in both IS 1905 and codes like EN 1996 is based on similar principles, combining the initial shear strength (cohesion) of the mortar joint with a component related to the frictional resistance from pre-compression (vertical dead load).
Parameter Comparison
Parameter
IS Value
International
Source
Design Philosophy
Working Stress Design (WSD)
Limit State Design (LSD)
EN 1996-1-1
Material Safety Factor (Masonry Compression)
A global factor of safety is embedded into permissible stresses (typically around 3-4).
Partial safety factor (γM) is applied. Value ranges from 1.5 to 3.0 depending on manufacturing and construction control.
EN 1996-1-1
Basic Compressive Strength Basis
Tabulated value based on unit strength and mortar grade (e.g., 0.96 N/mm² for 10 MPa unit & M1 mortar).
Calculated via formula, e.g., fk = K * fb^α * fm^β. Design strength is then fd = fk / γM.
EN 1996-1-1
Slenderness Ratio Limit (Single Storey Wall)
Limited to 27 for walls in cement mortar (1:6) or richer.
No absolute prescriptive limit; capacity is reduced by a factor (Φ) which becomes very small for high slenderness.
EN 1996-1-1
Modulus of Elasticity (E)
E = 550 x Permissible Compressive Stress (fc)
E = K x Characteristic Compressive Strength (fk), where K is a constant (e.g., 1000 for clay units).
EN 1996-1-1
Permissible Shear Stress (at zero compressive stress)
0.1 N/mm² (with a factor of 1.5 increase for in-plane bending)
Characteristic initial shear strength (fvk0) is specified, e.g., 0.1 to 0.3 N/mm² depending on mortar type.
EN 1996-1-1
Permissible Bending Tensile Stress (for wind on wall panel)
0.07 N/mm² for M1 mortar (1:6 Cement:Sand)
Characteristic flexural strength (fxk1) is specified, e.g., 0.1 N/mm² for general purpose mortar with clay units.
EN 1996-1-1
⚠ Verify details from original standards before use
Key Values6
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
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.