CONCRETE
Formwork Stripping Time (Removal Schedule)
Minimum time before formwork can be safely removed per IS 456 Cl. 11.3 — depends on member type, climate, and concrete strength.
Also calledstripping timeformwork strippingshuttering removal timeis 456 formwork removaldeshuttering time
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CODES
Definition
Formwork stripping time per IS 456 Cl. 11.3 (Ordinary Portland Cement, no admixture): vertical surfaces (walls, columns, sides of beams) = 16-24 hours; soffit of slabs (props left under) = 3 days; soffit of slabs (props removed) = 7 days; soffit of beams (props left under) = 7 days; soffit of beams (props removed) = 14 days; props to slabs spanning ≤ 4.5 m = 7 days; props to beams + slabs spanning > 4.5 m = 14 days. For mineral admixed cements (PPC, PSC) or cold weather, extend by 50%.
Typical values
Vertical surfaces (walls, column sides)16-24 hours
Soffit of slab (with props)3 days
Soffit of slab (no props)7 days
Soffit of beam (with props)7 days
Soffit of beam (no props)14 days
Props to slab ≤ 4.5m7 days
Props to beam/slab > 4.5m14 days
PPC/PSC cement+50% time
Where used
- Site formwork cycle planning
- Cube test schedule (release strength)
- Re-shoring decisions
Acceptance / threshold
Per IS 456 Cl. 11.3 — stripping permitted only when concrete attains sufficient strength to carry its own weight + construction loads (typically 70-100% of design strength for soffit forms).
Site example
M25 slab cast Monday morning: vertical sides strippable Tuesday morning (24 h); slab soffit strippable Thursday IF props retained (3 days); props removable next Monday (7 days).
Frequently asked
When can formwork be removed?
Per IS 456 Cl. 11.3 with OPC: walls/sides 16-24 h, slab soffit (props left) 3 days, slab soffit (no props) 7 days, beam soffit (no props) 14 days. Add 50% for PPC/PSC cement.
Why are props left under slab soffit longer than the shuttering?
After 3 days the concrete supports its own weight but not full construction load. Props redistribute load until 7-14 days when concrete reaches near-design strength.
Related terms
Laitance
Weak, porous layer of cement fines and water on concrete surface. Must be removed before next pour to ensure bond.
Formwork / Shuttering
Stripping time: slab 7d, beam soffit 14d, column 16-24h
Creep Coefficient of Concrete (θ)
Ratio of creep strain to elastic strain under sustained load — per IS 456 Cl. 6.2.5.1 — depends on age at loading and humidity.
Concrete Curing
Min 7 days for OPC, 10 days for PPC, 14 days for sulphate-resistant
Self-Compacting Concrete (SCC)
Highly fluid concrete that flows under its own weight, fills formwork, and consolidates without vibration.
High Strength Concrete (HSC)
Concrete with characteristic strength above M60. Requires silica fume, low w/c (<0.35), and quality aggregate.
RCC (Reinforced Cement Concrete)
Concrete with steel reinforcement. Per IS 456:2000.
Honeycomb in Concrete
Voids in concrete from poor compaction or formwork leakage. Repair with grouting; severe cases require demolition.
Creep & Shrinkage (Concrete)
Time-dependent deformation of concrete under sustained load
fck (Characteristic Strength)
5% probability lower limit at 28 days