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).

IS 15647

: 2006

Timber Formwork for Concrete - Code of Practice

CurrentFrequently UsedCode of PracticeBIMStructural Engineering · Scaffolding, Formwork and Construction Equipment

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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.

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

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.