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IS 1080:1985 is the Indian Standard (BIS) for design and construction of shallow foundations in soils (other than raft, ring and shell). This code sets out the guidelines for the design and construction of shallow foundations, such as pad footings, strip footings, and masonry foundations in soils. It establishes minimum depths, base dimensioning rules, and construction practices, though it explicitly excludes raft, ring, and shell foundations.
Code of Practice For Design And Construction Of Shallow Foundations In Soils (Other Than Raft, Ring And Shell)
! IS 1080 must be read in conjunction with IS 1904 (General requirements for design and construction of foundations).
! The minimum depth of 500 mm is a baseline; engineers must still ensure that the foundation bypasses topsoil, roots, and loose matter to reach a competent stratum.
! For plain concrete footings, ensure the base projection does not exceed the thickness of the footing to keep the stress dispersion within safe limits.
Eurocode 7: Geotechnical design - Part 1: General rules
Covers limit state design principles for shallow foundations, including bearing resistance and settlement.
IBC 2021, Chapter 18ICC (US)
MediumCurrent
International Building Code, Chapter 18: Soils and Foundations
Provides prescriptive and performance-based requirements for foundation design and allowable bearing pressures.
BS 8004:2015+A1:2020BSI (UK)
MediumCurrent
Code of practice for foundations
Provides UK-specific non-contradictory complementary information for use with Eurocode 7.
BS 8004:1986BSI (UK)
HighWithdrawn
Code of practice for foundations
Was the primary British standard for all foundation types, using an allowable stress design approach similar to IS 1080.
Key Differences
≠IS 1080 uses an Allowable Stress Design (ASD) approach with a global Factor of Safety (typically 2.5-3.0), whereas modern standards like Eurocode 7 use a Limit State Design (LSD) approach with partial factors on actions, materials, and resistances.
≠For eccentrically loaded foundations, IS 1080 restricts eccentricity to B/6 to avoid tension. Eurocode 7 allows for larger eccentricities by using the 'effective area' method, where calculations are based on a reduced foundation width (B' = B - 2e).
≠IS 1080 provides a single empirical formula for settlement calculation based on SPT-N values. Modern codes advocate for more rigorous methods (e.g., oedometer, elastic theory) and focus on checking against project-specific serviceability limits rather than prescribing one calculation method.
≠The treatment of the water table in IS 1080 (via IS 6403) involves applying a simple correction factor 'W''. In contrast, Eurocode 7 and other modern standards incorporate the effect of water by using effective stress principles directly in the bearing capacity and settlement calculations.
Key Similarities
≈All standards are based on the same fundamental soil mechanics principles for bearing capacity, derived from the work of Terzaghi, Meyerhof, and Vesic, using an equation form involving cohesion, surcharge, and soil weight components (Nc, Nq, Nγ).
≈Both IS 1080 and its international counterparts recognize that foundation design must satisfy two primary criteria: ultimate bearing capacity (a strength/safety check) and settlement (a serviceability check).
≈The scope of all standards covers the same conventional shallow foundation types, including isolated column footings, combined footings, and strip or wall footings.
≈All codes, Indian and international, emphasize the critical importance of a thorough geotechnical site investigation to determine the soil parameters that form the basis of the foundation design.
Parameter Comparison
Parameter
IS Value
International
Source
Design Philosophy
Allowable Stress Design (ASD) with a global Factor of Safety.
Limit State Design (LSD) using partial safety factors on loads and resistances.
EN 1997-1
Factor of Safety on Bearing Capacity
Minimum 2.5 (can be reduced by 25% for wind/seismic cases).
Not directly comparable. Partial factors are used, e.g., a resistance factor (γR;v) of 1.4 on bearing resistance for DA1-C2.
EN 1997-1
Minimum Foundation Depth
500 mm below ground level (Clause 7.1).
No absolute minimum specified; depth must be below topsoil, organic matter, and local frost line.
IBC 2021
Permissible Total Settlement (Isolated Footing on Sand)
50 mm (as per IS 1904, referenced by IS 1080).
No single codified value; project-specific. Typically 25-50mm is a common design limit.
General Practice / EN 1997-1
Permissible Total Settlement (Isolated Footing on Clay)
75 mm (for plastic clays, as per IS 1904).
No single codified value; project-specific and dependent on structure's tolerance to movement.
General Practice / EN 1997-1
Eccentricity Limit (e)
Must be less than or equal to B/6 to maintain compressive stress over the entire footing area.
Can exceed B/6; design is based on a reduced 'effective' foundation area A' = L' * B'.
EN 1997-1
Minimum Footing Edge Thickness
150 mm for footings on soil (Clause 11.1.2).
150 mm (6 inches) for footings on soil (governed by structural concrete code).
ACI 318-19
⚠ Verify details from original standards before use
Key Values4
Quick Reference Values
minimum depth of foundation0.5 m below natural ground level
minimum thickness at edge of reinforced footing150 mm