| S.No. | Field / Checkpoint | Reference | Status |
|---|---|---|---|
| A. ELEMENT + POUR DETAILS | |||
| A1 | Element ID + pour date + curing days completed Acceptance: Documented | Per IS 456 Table 7 | OK NC NA |
| A2 | Grade + characteristic strength achieved (cube test 7-day / 14-day) Acceptance: Strength data attached | Per IS 456 Cl. 16.5 | OK NC NA |
| B. DE-SHUTTERING TIMINGS (IS 456 TABLE 7) | |||
| B1 | Side formwork (column, beam side) — 16-24 hrs Acceptance: Per code | IS 456 Table 7 | OK NC NA |
| B2 | Slab soffit (≤ 6m span) — 14 days Acceptance: Strength verified | Cube strength ≥ 50% fck | OK NC NA |
| B3 | Slab soffit (> 6m span) — 21 days Acceptance: Strength verified | Cube strength ≥ 70% fck | OK NC NA |
| B4 | Beam soffit (≤ 6m span) — 14 days; (> 6m) — 21 days Acceptance: Per code | IS 456 Table 7 | OK NC NA |
| B5 | Cantilever — 28 days minimum Acceptance: Per code | IS 456 Table 7 | OK NC NA |
| C. APPROVAL | |||
| C1 | Strength verified vs required + visual inspection Acceptance: Approved by QC + consultant | No surface defects after removal | OK NC NA |
| C2 | Permit to de-shutter issued Acceptance: Permit number assigned | Triple sign | OK NC NA |
Formwork (shuttering) removal is a structurally critical operation — premature removal causes excessive deflection, surface damage, or structural collapse. IS 456:2000 Clause 11.3 specifies minimum stripping times based on concrete grade, ambient temperature, structural element.
The De-shuttering Permit is the formal site-level authorization. Before any formwork strip: 1. Site engineer verifies concrete age vs minimum stripping time 2. Cube test results reviewed (if early stripping requested) 3. Backpropping arrangement verified 4. PMC + structural consultant signature obtained 5. Permit issued; only then crew authorized to strip
Without permit discipline, individual workers / supervisors strip on judgement; collapse incidents result. For multi-storey buildings + cantilevers, mandatory permit prevents 100% of premature-stripping incidents.
Permit content: - Project + member reference (Column C-15 / Slab S-4 / Beam B-12) - Concrete grade + ambient temperature - Pour date + age in days at proposed stripping - IS 456 minimum stripping time per element (cross-reference table) - Cube test reference + 7-day / 28-day strength results - Backpropping plan for multi-storey works - Approval: site engineer + PMC + (for cantilevers) structural consultant - Strip date + crew supervisor + sign-off
IS 456 minimum stripping times (15°C+ ambient, OPC concrete): - Vertical formwork (column, wall, beam side): 16-24 hours - Slab soffit (props left): 3 days - Beam soffit (props left): 7 days - Slab props (≤ 4.5 m span): 7 days - Beam props (≤ 6 m span): 14 days - Cantilever soffit + supports: 28 days
For early stripping: cube test must show ≥ 70% of design strength + structural consultant approval.
1. Premature stripping — formwork removed before IS 456 minimum age; cracking + deflection. 2. No cube test for early stripping — assumption of strength without verification. 3. No backpropping — slab stripped while floor above is being poured; excessive deflection. 4. Cantilever stripped early — most catastrophic failure mode; minimum 28 days for cantilevers absolute. 5. Cold weather not compensated — winter pour stripped per summer schedule; strength inadequate. 6. PPC concrete treated as OPC — PPC needs longer curing + stripping time. 7. No engineer sign-off — strip decision left to crew foreman; no accountability. 8. Visual inspection only — no measurement of deflection / cracking immediately post-strip.
Companion formats: - Formwork Removal Schedule (FMT-SIT-024) — schedule planning - Daily Concrete Pour Register (FMT-SIT-015) — pour records - Curing Register (FMT-SIT-025) — curing duration - Cube test register (cross-reference)
Codes: - IS 456:2000 — RCC code; Clause 11.3 (formwork) - IS 14687:1999 — Falsework for Concrete Structures - IS 4990:2011 — Plywood for Concrete Shuttering - IS 516 Part 1 Sec 1:2021 — Cube compressive strength