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
Related on InfraLens
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 concrete terms
Concrete Mix Design
Proportioning of cement, water, aggregates per IS 10262
Concrete Grades (M15-M80)
M20=20 N/mm² characteristic strength at 28 days
Water-Cement Ratio (w/c)
Mass of water to mass of cement. 0.40-0.55 typical.
Concrete Cover
Min concrete from rebar to surface (15-50mm per exposure)
Concrete Curing
Min 7 days for OPC, 10 days for PPC, 14 days for sulphate-resistant
Slump Test / Workability
25-150mm slump per application (IS 1199)
Cube Test (Compressive Strength)
150mm cube compressive strength test at 7/28 days (IS 516)
Concrete Admixtures
Plasticizers, accelerators, retarders per IS 9103