What is the minimum time to remove formwork from a concrete column?

For vertical faces like columns, walls, and large beam sides, formwork can be removed after 16 to 24 hours. (Clause 11.2)

When can I remove the bottom formwork (soffit) of a 4m slab?

Soffit formwork can be removed after 3 days if props are re-fixed immediately. The props themselves can be removed after 7 days for spans up to 4.5m. (Table 2)

What are the main loads to consider when designing formwork?

The design must account for the dead load of wet concrete, self-weight of the formwork, live loads from workers and equipment, and the lateral pressure exerted by the fresh concrete. (Clause 6)

What is the acceptable tolerance for the dimensions of a concrete beam?

The tolerance for cross-sectional dimensions of members like beams and columns is +12 mm and -6 mm. (Table 1)

IS 10792

: 1984

Recommendations for Formwork for Concrete

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

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This code provides recommendations for the design, fabrication, erection, and stripping of formwork for in-situ concrete structures. It covers materials, design loads, construction practices, tolerances, and minimum time periods before striking formwork to ensure safety and quality.

Provides recommendations for the design, construction, and removal of formwork for concrete structures.

Quick Reference Values

Stripping time for vertical faces (columns, walls)16 to 24 hours

Stripping time for slab soffits (props re-fixed immediately)3 days

Stripping time for beam soffits (props re-fixed immediately)7 days

Stripping time for slab props (span up to 4.5m)7 days

Stripping time for beam/arch props (span up to 6m)14 days

Maximum deviation from vertical for columns/walls±6 mm per 3 m height

Tolerance in cross-sectional dimensions of columns/beams+12 mm / -6 mm

Key Formulas

P = γh — Basic formula for lateral pressure of fluid concrete (where P is pressure, γ is unit weight, h is depth of fluid concrete)

Practical Notes

This 1984 version has been superseded by IS 10792:2022. The new version should be consulted for current projects as it contains updated provisions.

Stripping times are highly dependent on ambient temperature and type of cement. The code specifies values for temperatures above 15°C using Ordinary Portland Cement; adjustments are needed for other conditions.

For multi-story construction, ensure that the supporting floors have gained sufficient strength before being subjected to the load of freshly placed concrete from the floor above.