| S.No. | Field / Checkpoint | Reference | Status |
|---|---|---|---|
| A. ELEMENT SCHEDULE | |||
| A1 | Element ID + pour date + grade + span Acceptance: Tabulated | Per project tracker | OK NC NA |
| A2 | De-shutter date (per IS 456 Table 7) Acceptance: Per element type | Per code | OK NC NA |
| B. DEPENDENCY | |||
| B1 | Reshoring schedule (for upper-floor slabs) Acceptance: Per shoring plan | Distribute load to lower floors | OK NC NA |
| B2 | Cube strength verification before each removal Acceptance: Test result attached | IS 456 Cl. 16.5 — 70% fck for major elements | OK NC NA |
| C. APPROVALS | |||
| C1 | De-shutter permit raised for each element Acceptance: Permit log | FMT-SIT-022 process | OK NC NA |
Formwork (shuttering) is the temporary structure that supports fresh concrete until it gains sufficient strength to support its own weight. Premature formwork removal causes excessive deflection, surface damage, or in worst cases, structural collapse. Late removal wastes formwork (kept idle longer than needed), delays construction, and increases hire/depreciation costs.
IS 456:2000 Clause 11.3 specifies the minimum formwork stripping times based on concrete grade + ambient temperature + structural element type. The Formwork Removal Schedule tracks each pour against these mandatory minimums + actual planned removal date.
For ordinary Portland cement (OPC) concrete at 15°C ambient temperature minimum:
| Element | Minimum stripping time | |---|---| | Vertical formwork (column / wall / beam side) | 16-24 hours | | Soffit formwork — slabs (props left) | 3 days | | Soffit formwork — beams (props left) | 7 days | | Props to slabs (spans ≤ 4.5 m) | 7 days | | Props to slabs (spans > 4.5 m) | 14 days | | Props to beams (spans ≤ 6 m) | 14 days | | Props to beams (spans > 6 m) | 21 days | | Cantilevers — main soffit + supports | 28 days |
Adjustments for low temperature: time increases proportionally below 15°C. Multiply by 2 at 5°C; 3 at 0°C.
For PPC / blended cements: add 1-3 days to all minimums (slower strength gain).
For high-strength / accelerated concrete: may be reduced; document with cube test data + design approval.
Per-pour entry: - Pour ID (column / slab / beam reference) - Pour date + concrete grade - Ambient temperature category - Formwork type (column / wall / slab soffit / props / beam) - IS 456 minimum stripping time (auto-calculated from above) - Cube test results (28-day not waited for; use 7-day if available) - Actual stripping date - Sign-off: PMC engineer + contractor + structural engineer (for cantilevers + premium projects)
Use of cube test for early removal: per IS 456 Cl. 11.3.1, if cube tested at intermediate age shows the concrete has achieved 70% of design strength, early stripping is permitted. Cube test certificate must be attached to the schedule.
Backpropping: even when soffit forms are removed, backprops at strategic spacing are typically retained for additional 7-14 days to support live loads during subsequent floor construction.
Sequence for multi-storey buildings: typically 3-floor cycle — current pour at top, backprops 1-2 floors below, formwork fully removed 3 floors below. Sequential strip + relocate.
1. Early stripping cantilever — premature stripping of cantilever soffit (before 28 days) is the #1 cause of structural cracking in cantilever balconies + chajjas. The schedule's mandatory 28-day timer prevents this.
2. Premature column stripping — vertical column form stripped within 4-8 hours causes surface honeycomb + dimensional loss. Minimum 16-24 hours mandatory.
3. No cube test before early stripping — stripping early without verifying concrete strength = guesswork. Mandate cube test + 70% strength verification before any deviation from IS 456 minimums.
4. Insufficient backpropping — full formwork removed; floor above poured; live load causes excessive deflection on the unrepaired floor below. Backpropping schedule is critical for multi-storey work.
5. No temperature compensation — winter pours stripped per summer schedule cause early-age cracking due to inadequate strength gain. Always adjust for ambient.
6. No formwork inventory tracking — formwork not returned to stores promptly; lost / damaged not replaced; costs accumulate.
7. No supervisor sign-off — stripping decisions left to crew foreman. Mandate engineer-level sign-off for all stripping events.
Codes: - IS 456:2000 — Plain and Reinforced Concrete (the primary; Clause 11.3 on formwork) - IS 14687:1999 — Falsework for Concrete Structures — Guidelines (for formwork design) - IS 4990:2011 — Plywood for Concrete Shuttering Work — Specification - IS 10262:2019 — Concrete Mix Design (strength gain curves) - IS 516 Part 1 Sec 1:2021 — Cube compressive strength test
Companion formats: - Daily Concrete Pour Register (FMT-SIT-015) — pour-by-pour log - Curing Register (FMT-SIT-025) — companion curing tracker - Cube test register (QC-CON-REG) — strength data for early-stripping decisions