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IS 1642:1989 Part 2 is the Indian Standard (BIS) for fire safety of buildings (part 2: details of construction). This code establishes the detailed construction practices required to ensure adequate passive fire safety in buildings. It specifies fire resistance ratings for various structural elements, compartmentation rules to prevent fire spread, and construction requirements for walls, floors, roofs, and staircases.
Specifies construction details for fire resistance of building elements, including walls, floors, and roofs.
Quick Reference — Top IS 1642 Part 2:1989 Values
Key fire resistance ratings, minimum element thicknesses, reinforcement cover, and construction details for steel, concrete, and masonry structures.
✓ Verified 2026-04-27
Reference
Value
Clause
Min dimension, RC Column (4h)— Minimum dimension for a 4-hour fire resistance rating.
450 mm
Cl. 5.2.1 (Table 5)
Min dimension, RC Column (2h)— Minimum dimension for a 2-hour fire resistance rating.
300 mm
Cl. 5.2.1 (Table 5)
Min thickness, RC Slab (2h)— For solid reinforced concrete slabs.
125 mm
Cl. 5.2.3 (Table 7)
Min thickness, RC Slab (1h)— For solid reinforced concrete slabs.
95 mm
Cl. 5.2.3 (Table 7)
Min cover, RC Beam (SS, 2h)— For simply supported beams to achieve 2-hour fire resistance.
45 mm
Cl. 5.2.4 (Table 8)
Min cover, RC Beam (Continuous, 2h)— For continuous beams to achieve 2-hour fire resistance.
35 mm
Cl. 5.2.4 (Table 9)
Min cover, RC Slab (SS, 1h)— For simply supported slabs to achieve 1-hour fire resistance.
20 mm
Cl. 5.2.4 (Table 10)
Min cover, RC Slab (Continuous, 1h)— For continuous slabs to achieve 1-hour fire resistance.
International Building Code, Chapter 7: Fire and Smoke Protection Features
Provides prescriptive and performance requirements for fire-resistance-rated construction of building elements, including walls, floors, and openings.
BS 9999:2017BSI (UK)
HighCurrent
Fire safety in the design, management and use of buildings. Code of practice
Offers a risk-based approach to fire safety design, including detailed guidance on structural protection and compartmentation.
EN 1992-1-2:2004CEN (European Union)
MediumCurrent
Eurocode 2: Design of concrete structures - Part 1-2: General rules - Structural fire design
Focuses specifically on the fire design of concrete structures, providing advanced calculation methods and tabulated data, which is a subset of IS 1642's scope.
NFPA 220NFPA (US)
MediumCurrent
Standard on Types of Building Construction
Defines building construction types based on the fire resistance of materials, a concept also used in the IS code framework.
Key Differences
≠IS 1642:1989 is almost entirely prescriptive, providing tables of minimum dimensions and material covers for specific fire ratings. Modern codes like the IBC and BS 9999 allow for performance-based design, where fire engineering principles can be used to demonstrate equivalent safety, offering more design flexibility.
≠The Indian standard is based on research and testing methods from the 1980s. International equivalents like the Eurocodes are regularly updated to incorporate new research on material behavior at high temperatures, advanced calculation models (e.g., for thermal and structural analysis), and more refined testing standards.
≠Modern international codes provide detailed guidance on a wider range of fire protection systems and materials, such as intumescent coatings, modern fire-stopping products for service penetrations, and rated gypsum board assemblies, which are not explicitly covered in IS 1642:1989.
≠The classification of building types in IS 1642 (Type 1 to 4) is simpler than the five construction types (Type I to V, with A/B sub-classifications) defined in the IBC and NFPA 220, which provide a more granular definition of combustibility and fire resistance requirements.
Key Similarities
≈All standards are based on the fundamental principle of compartmentation, which involves dividing a building into fire-resistant compartments using rated walls, floors, and ceilings to contain a fire to its area of origin for a specified duration.
≈Both the IS code and its international counterparts use the concept of a Fire Resistance Rating (FRR), expressed in hours or minutes, to quantify the performance of a building element (e.g., wall, column, floor) when exposed to a standard fire test.
≈There is a common emphasis on protecting openings in fire-rated assemblies. All codes mandate the use of rated fire doors, windows, and dampers, and require fire-stopping for penetrations to maintain the integrity and insulation of the fire barrier.
≈All codes provide prescriptive tables that link the fire resistance duration to the minimum thickness of walls/slabs and the minimum concrete cover for reinforcing steel in structural elements, even though the specific values may differ.
Parameter Comparison
Parameter
IS Value
International
Source
Min. thickness for 1-hour rated reinforced concrete slab
100 mm
89 mm (3.5 inches) for siliceous aggregate concrete
IBC 2021, Table 722.3.2(1)
Min. concrete cover for a 2-hour rated restrained RC beam
40 mm
25 mm (1 inch)
IBC 2021, Table 722.2.1(1)
Min. dimension of a 3-hour rated reinforced concrete column
400 mm
356 mm (14 inches)
IBC 2021, Table 722.2.2.1
Min. thickness for a 4-hour rated solid clay brick load-bearing wall (unplastered)
200 mm
178 mm (7 inches) nominal thickness
IBC 2021, Table 722.3.2
Min. thickness for a 2-hour rated solid concrete load-bearing wall (siliceous aggregate)
160 mm
152 mm (6.0 inches)
IBC 2021, Table 722.3.2(1)
⚠ Verify details from original standards before use
Key Values6
Quick Reference Values
Minimum thickness of load-bearing solid brick wall for 1-hour fire resistance100 mm
Minimum thickness of load-bearing solid brick wall for 4-hour fire resistance200 mm
Minimum dimension of fully exposed RC column for 2-hour fire resistance300 mm
Minimum concrete cover for RC columns for 2-hour fire resistance40 mm
Minimum width of RC beam for 2-hour fire resistance200 mm
Minimum thickness of solid RC floor slab for 2-hour fire resistance125 mm
Tables & Referenced Sections
Key Tables
Table 1 - Nominal Minimum Thickness of Masonry Walls for Fire Resistance
Table 2 - Fire Resistance of Reinforced Concrete Columns
Table 3 - Fire Resistance of Reinforced Concrete Beams
Table 4 - Fire Resistance of Reinforced Concrete Floors