When can you remove the shuttering from a slab, beam or column? Strip it too early and the slab sags or cracks; leave it too long and the job stalls and you pay extra rent for props and plates. This guide gives the formwork removal periods from IS 456:2000 clause 11.3, explains when they need to be longer, and includes a free calculator that turns your casting date into removal dates.
| Vertical faces (columns, walls, beam sides) | 16 – 24 hours |
|---|---|
| Slab soffit (props re-fixed at once) | 3 days |
| Beam soffit (props re-fixed at once) | 7 days |
| Props under slabs up to 4.5 m span | 7 days |
| Props under slabs over 4.5 m span | 14 days |
| Props under beams & arches up to 6 m | 14 days |
| Props under beams & arches over 6 m | 21 days |
The basic rule behind the table
IS 456 cl. 11.3 says formwork must not be released until the concrete has reached a strength of at least twice the stress it will carry at the time of removal. The day counts in the table are the code’s default way of meeting that rule for OPC in normal temperatures. If you test cubes cured alongside the structure, you can decide stripping from their strength instead of from days alone.
Soffit removal vs prop removal
Many site disputes come from mixing these two up:
- Soffit formwork is the plates or plywood directly under the slab or beam. The code lets you remove it early (3 days for slabs, 7 days for beams) only if props are re-fixed immediately so the member is still supported.
- Props are the vertical supports. They carry the member until it can carry itself, so they stay longer: 7 or 14 days for slabs, 14 or 21 days for beams, depending on span.
If your shuttering system does not allow re-propping, keep the soffit in place until the prop removal period is over.
Free shuttering removal date calculator
When to wait longer than the code table
- PPC, PSC (slag) or fly ash-blended cement: early strength is lower than OPC. IS 456 cl. 11.3.1 says the periods should be modified for other cements. Most PPC is used on house sites, so this applies to most of them.
- Cold weather: strength gain slows a lot in cold weather, for example in hill areas in winter.
- Cantilevers and chajjas: these depend on the back span for balance. Never remove their props early.
- Construction loads on top: if the next floor is being shuttered and cast on top, the lower floor carries wet concrete, workers and stacked material. Keep back-props (reshoring) under the lower slab.
- Poor curing: a slab that dried out early is weaker than its age suggests. See curing of concrete.
How to strip formwork safely
- Remove side forms first (columns, beam sides), then slab soffits, then beam soffits.
- De-prop slabs from the middle of the span towards the supports, and cantilevers from the free end towards the support.
- Loosen props gradually; do not knock them out with a hammer or let plates drop onto the slab below.
- Check for sagging, cracks or honeycombing as soon as the surface is exposed. See honeycombing in concrete.
- Keep curing after stripping: exposed faces dry out fast.
Frequently asked questions
After how many days can slab shuttering be removed?
The slab soffit can come off after 3 days if props are re-fixed immediately. The props stay for 7 days for spans up to 4.5 m and 14 days for spans over 4.5 m (IS 456 cl. 11.3.1, OPC).
When can column shuttering be removed?
Vertical formwork to columns can be removed after 16 to 24 hours.
When can beam props be removed?
After 14 days for beams spanning up to 6 m and 21 days for spans over 6 m, for OPC in normal weather.
Is the removal time different for PPC cement?
Yes. IS 456 says the periods should be modified for other cements and lower temperatures. PPC gains strength more slowly than OPC, so wait longer or strip based on field-cured cube results.
Related guides
- Curing of Concrete
- Concrete Cube Test (IS 516 & IS 456)
- Column, Beam & Footing Size for G+1 / G+2 House
- Cement Bags in 1 m³ of Concrete
Reference: IS 456:2000, clause 11.3 (Stripping Time) and 11.3.1.
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