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IS 9494:1980 is the Indian Standard (BIS) for concrete formwork - code of practice for safety. This code provides safety guidelines for the design, fabrication, erection, and stripping of concrete formwork. It specifies minimum loads, material requirements, and procedural checks to ensure the stability of temporary structures and the safety of workers on construction sites.
Lays down safety requirements for the design, erection, use, and dismantling of concrete formwork.
Overview
Status
Current
Usage level
Frequently Used
Domain
Structural Engineering — Scaffolding, Formwork and Construction Equipment
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! This is an old standard (reaffirmed in 2018), so manufacturer specifications for modern proprietary formwork systems should also be consulted and may govern.
! The role of a 'competent person' for supervision and inspection, as mentioned in the code, is critical and should be formally assigned on site.
! While this code covers formwork safety, minimum striking times for formwork are primarily specified in IS 456, based on concrete strength development.
BS 5975:2019BSI - British Standards Institution, UK
HighCurrent
Code of practice for temporary works procedures and the permissible stress design of falsework
Focuses on procedural control and safety management of temporary works, including formwork and falsework.
OSHA 1926 Subpart QOSHA - Occupational Safety and Health Administration, USA
HighCurrent
Concrete and Masonry Construction
Provides mandatory safety regulations for concrete formwork construction, inspection, and removal in the US.
AS 3610.1:2018Standards Australia, Australia
MediumCurrent
Formwork for concrete - Part 1: Specifications
Covers design, fabrication, erection, and stripping of formwork, including significant safety and performance requirements.
CSA S269.1-16 (R2021)CSA Group, Canada
MediumCurrent
Falsework and formwork
A comprehensive standard covering design, construction, and safety of falsework and formwork.
Key Differences
≠IS 9494:1980 is largely prescriptive, providing specific guidance on materials like timber and nails. Modern standards like BS 5975 are performance-based, focusing on procedural controls, risk assessment, and design verification rather than specific material types.
≠Modern standards (e.g., BS 5975's 'Temporary Works Coordinator') define explicit roles, responsibilities, and required competencies for personnel. IS 9494 uses more general terms like 'competent person' or 'responsible person' without a structured framework for their appointment and duties.
≠International codes like AS 3610.1 provide detailed formulae and values for calculating construction loads, dynamic effects of concrete placement, and wind loads. IS 9494 offers very general guidance on loads, often deferring to other codes for detailed design.
≠Stripping criteria in IS 9494 are primarily time-based (e.g., a set number of days). Most current international standards mandate stripping based on the concrete achieving a specified minimum strength, verified by testing, which is a more reliable measure.
Key Similarities
≈All standards, including IS 9494, emphasize the critical importance of providing stable foundations or base plates (mudsills) on firm ground to prevent settlement of the formwork structure.
≈The fundamental requirement for adequate diagonal bracing in both longitudinal and transverse directions to ensure stability against lateral forces is a core safety principle shared by IS 9494 and all its modern international equivalents.
≈IS 9494 specifies a multi-stage inspection process (before reinforcement, before concrete, and during concreting). This principle is mirrored in standards like OSHA 1926, which also requires inspections prior to, during, and after the pour.
≈A universal principle across all codes is the prohibition of formwork removal (stripping) until the concrete has gained sufficient strength to support its own weight and any superimposed loads.
Parameter Comparison
Parameter
IS Value
International
Source
Minimum Horizontal Load for Bracing
Not less than 2% of the total vertical load at that level.
Not less than 2.5% of the characteristic vertical dead load.
AS 3610.1:2018
Minimum Construction Live Load (on working platforms)
75 kg/m² (approx. 0.75 kPa) for light duty access.
1.0 kPa for areas accessible to personnel only.
AS 3610.1:2018
Primary Basis for Formwork Stripping
Time-based tables based on ambient temperature and cement type.
Concrete achieving a specified minimum compressive strength (e.g., 15 MPa for many suspended elements).
AS 3610.1:2018
Inspection Stages
1) Before placing reinforcement, 2) Before placing concrete, 3) During concreting.
1) Immediately prior to concrete placement, 2) During placement, 3) Immediately after placement.
OSHA 1926.703(b)(1)
Prop Spacing
Generally recommends spacing not to exceed 1.0 m.
Not specified; determined by design calculations based on loads and member capacity.
General practice in BS 5975 / AS 3610.1
Design Responsibility for Formwork
To be designed by a responsible person, with drawings available on site.
Must be designed and documented by a qualified engineer, with independent design checks for complex schemes.
BS 5975:2019
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Minimum live load on formwork deck200 kg/m2
Minimum concentrated load on formwork deck450 kg
Minimum horizontal load for bracing design2% of total vertical dead load
Factor of safety against overturning1.5
Maximum permissible deflection in formworkspan/270 or 3 mm, whichever is less
Key Formulas
P = wH — Formula for lateral pressure of fresh concrete (where P is pressure, w is density, and H is height of fluid concrete)
What is the minimum live load to be considered for formwork design?+
200 kg/m2 on the plan area to account for workers and equipment, or a concentrated load of 450 kg, whichever produces a greater effect (Clause 5.2.2).
Who is responsible for inspecting the formwork before concreting?+
A competent person must inspect and certify the formwork for conformity with drawings, safety, and rigidity before any concrete is placed (Clause 7.1).
What are the general rules for stripping side forms?+
Side forms for columns, walls, and beams can generally be removed after 16 to 24 hours, ensuring the process does not damage the concrete (Clause 8.3).
What is the design requirement for bracing against horizontal loads?+
The formwork system should be designed to resist a minimum horizontal load of 2% of the total dead load of the structure and formwork (Clause 5.2.3).