Overview
Decking sheets, also known as composite metal decks or profiled steel decks, are widely used in modern construction for slab systems in residential, commercial, and industrial buildings. When topped with concrete, the decking sheet acts as both a formwork during construction and as reinforcement in the composite slab system, enhancing overall structural efficiency.
1. Design Principle
Decking sheet with concrete forms a composite floor slab, utilizing the high tensile strength of steel and the compressive strength of concrete. The profiled steel sheet provides the tensile reinforcement and also supports the wet concrete until it hardens.
2. Components of Composite Decking Slab
- Profiled Steel Sheet: Galvanized steel with embossed patterns for bond with concrete.
- Concrete Layer: Usually M25 or higher grade depending on structural requirement.
- Mesh or Reinforcement Bars: Placed over the decking sheet to control shrinkage and enhance flexural strength.
- Shear Studs (optional): Used in high-load areas to ensure composite action.
3. Common Decking Sheet Profiles
- Depth: 50mm, 75mm, or 100mm
- Thickness: 0.8mm to 1.2mm
- Width (Cover): 600mm to 1000mm (varies by manufacturer)
- Span: Typically up to 3.5m without temporary supports
4. Design Loads
As per IS 875 (Part 2) and IS 456:2000
- Live Load: 2 to 5 kN/m² depending on usage
- Dead Load: Self-weight of slab and finishes
- Construction Load: Temporary loading during concreting
5. Material Specifications
Decking Sheet
- Material: Cold rolled galvanized steel (IS 277 or equivalent)
- Yield Strength: 250–550 MPa
- Coating: Zinc (minimum 120 GSM)
Concrete
- Grade: M25 or M30 (based on structural requirements)
- Slump: 75–100 mm for pumped concrete
Reinforcement
- Welded wire mesh or TMT bars (Fe500/Fe550)
- Minimum shrinkage reinforcement: 0.12% of slab cross-sectional area (as per IS 456)
6. Construction Details
- Decking sheets are laid over steel or RCC beams.
- End laps are typically 150–200 mm, side laps fastened using self-drilling screws or shot pins.
- Temporary props may be used for longer spans until concrete gains strength.
- Concrete is poured over sheets, properly compacted and cured.
7. Advantages
- Quick installation reduces construction time.
- Acts as formwork—no need for separate shuttering.
- Reduces dead load compared to traditional slabs.
- Better fire resistance with fire-rated concrete topping.
- Cost-effective for large-span floors.
8. Code References
- IS 456:2000 – Plain and Reinforced Concrete Code
- IS 875 Part 1 & 2 – Load calculations
- IS 277 – Galvanized Steel Sheets
- ACI 318 / BS 5950 / Eurocode 4 – For international projects
Sample Cross-section Dimensions
| Parameter | Value |
|---|---|
| Deck Sheet Depth | 75 mm |
| Sheet Thickness | 1.0 mm |
| Concrete Thickness | 125 mm (overall) |
| Mesh Reinforcement | 8 mm @ 150 mm c/c |
| Concrete Grade | M25 |
Application Areas
- Multi-storey office buildings
- Shopping malls
- Mezzanine floors in warehouses
- Parking garages
- Residential slabs with large span
Conclusion
Composite deck slabs using decking sheets and concrete offer a reliable, economical, and fast-track construction solution. Proper detailing, material selection, and adherence to design standards ensure structural integrity and long-term performance.