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IS 15647:2006 is the Indian Standard (BIS) for timber formwork for concrete - code of practice. This code provides guidelines for the design, fabrication, erection, and stripping of timber formwork for concrete structures. It covers material specifications, design loads, permissible stresses in timber and plywood, and safe practices for erection and removal, including minimum striking times.
Provides guidelines for the design, construction, and removal of timber formwork for concrete structures.
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
! Always check the condition of timber and plywood for defects like knots, splits, and decay before use, as these significantly reduce load-bearing capacity.
! Ensure props are adequately braced in both longitudinal and transverse directions to prevent buckling, a common cause of formwork collapse.
! The striking times in Table 2 are 'suggested minimums' for ordinary Portland cement at ambient temperatures above 15°C. These must be increased in cold weather or when using blended cements or admixtures, with the final decision guided by concrete cube strength.
Both provide comprehensive guidance on the design, materials, construction, and safety of concrete formwork.
BS 5975:2019British Standards Institution (BSI), UK
HighCurrent
Code of practice for temporary works procedures and the permissible stress design of falsework
Both are codes of practice for temporary structures supporting concrete, though BS 5975 has a broader procedural focus.
AS 3610.1:2018Standards Australia, Australia
HighCurrent
Formwork for concrete - Part 1: Specifications
Both provide detailed specifications for the design, fabrication, erection, and stripping of concrete formwork.
EN 12812:2008European Committee for Standardization (CEN), Europe
MediumCurrent
Falsework - Performance requirements and general design
Both cover structural design of temporary supports, but EN 12812 focuses on the falsework (support system) rather than the form face.
Key Differences
≠IS 15647 primarily uses a permissible stress design (working stress) method for timber components, whereas modern standards like AS 3610 and BS 5975 increasingly incorporate or are used alongside limit state design principles.
≠BS 5975 mandates specific procedural roles like the Temporary Works Coordinator (TWC), which are not explicitly defined in IS 15647, making the UK standard more procedurally rigorous for site management.
≠Calculation of lateral pressure from fresh concrete in IS 15647 is based on prescriptive tables (Table 2) dependent on temperature and pour rate, while ACI 347R provides detailed formulas that account for more variables like admixtures and cement type.
≠Material specifications in IS 15647 reference Indian timber species and grades (e.g., from IS 883), which differ significantly from the timber species (e.g., Douglas Fir, Southern Pine) and grading rules (e.g., NDS) referenced in ACI 347R.
Key Similarities
≈All standards are fundamentally based on ensuring the formwork system has adequate strength to resist all imposed loads (vertical and lateral) and sufficient stiffness to maintain the concrete's shape within specified tolerances.
≈All codes require consideration of a common set of loads, including self-weight of forms and concrete, construction live loads (workers, equipment), and lateral pressure from fresh concrete.
≈Guidance on formwork removal (striking or stripping) is a key component in all standards, linking removal times to concrete strength gain, span, and the type of structural element.
≈All standards emphasize safety during the erection, use, and dismantling phases, including requirements for adequate bracing, foundations, and access for workers.
≈The concept of specifying and controlling deflection to ensure the quality of the final concrete finish and structural integrity is a common serviceability requirement across all standards.
Parameter Comparison
Parameter
IS Value
International
Source
Minimum Construction Live Load (deck)
2.0 kN/m² (for normal working area)
2.4 kN/m² (50 psf) for workers and equipment
ACI 347R-14
General Deflection Limit for Flexural Members
Span / 270
Span / 270 (for surfaces where finish is of consequence)
AS 3610.1:2018
Verticality Tolerance (up to 3m height)
±6 mm (as per referenced IS 456)
±6 mm (±1/4 inch per 10 ft)
ACI 117-10 (referenced by ACI 347R)
Horizontal Wind Load (Minimum)
Not less than 1.0 kN/m² of the vertical projection
Not less than 15 lbf/ft² (0.72 kN/m²), but requires calculation based on local codes (e.g., ASCE 7)
ACI 347R-14
Permissible Stress Increase for Wind Load
25% increase in permissible stresses for timber
Load combinations are used (Limit State Design), no direct stress increase factor is applied in the same way.
BS 5975:2019
Re-propping Requirement
Permitted, but loads on supporting slabs must be carefully checked.
Permitted, with detailed guidance on load distribution and checking capacity of supporting floors (backpropping).
AS 3610.1:2018
⚠ Verify details from original standards before use
Key Values6
Quick Reference Values
Maximum permissible deflection for formwork membersspan/270 or 5 mm, whichever is less
Minimum live load on formwork from workers/equipment1.5 kN/m²
Minimum concentrated live load on formwork2.0 kN
Minimum striking time for slab soffits (props refixed)3 days
Minimum striking time for beam soffits (props refixed)7 days
Permissible bending stress for Sal wood (Group B, inside location)16.1 N/mm²
Tables & Referenced Sections
Key Tables
Table 1 - Permissible Stresses for Timber
Table 2 - Suggested Minimum Time Before Striking Formwork
Key Clauses
Clause 5 - Materials
Clause 6 - Loads
Clause 7 - Design
Clause 11 - Striking of Formwork (Removal of Forms)
What is the minimum time to remove formwork for a concrete slab soffit?+
3 days if props are refixed immediately. For complete removal of props, it is 7 days for spans up to 4.5m and 14 days for spans over 4.5m (Table 2).
What live load should be considered for formwork design?+
A minimum uniformly distributed load of 1.5 kN/m² for workers and equipment, or a minimum concentrated load of 2.0 kN at any unfavorable point (Clause 6.2.2).
What is the maximum permissible deflection for formwork supporting wet concrete?+
The lesser of span/270 or 5 mm for members (Clause 7.3).