What is composite metal decking?

Composite metal decking is a profiled steel sheet (0.9-1.2mm thick) that acts as permanent formwork for in-situ concrete floor slabs. The deck profile has embossments that create a mechanical bond with the concrete, forming a composite slab that acts as a single structural element. It eliminates the need for traditional timber formwork and propping.

What depth of concrete topping do I need?

The minimum concrete topping above the top of the deck profile is 60mm for fire resistance and structural reasons. Typical total slab depths are: 130mm for TR60 deck, 150mm for TR80 deck. The total depth is the concrete topping minus the deck profile depth above the rib. Check BS EN 1994-1-1 for minimum requirements.

What are shear studs and why are they needed?

Shear studs (headed studs, typically 19mm diameter × 100mm long) are welded through the deck to the steel beam flange. They transfer horizontal shear between the concrete slab and the steel beam, creating composite action. This significantly increases the beam's load-carrying capacity and stiffness compared to a non-composite beam. Spacing is typically 150-300mm.

When does metal decking need propping during construction?

Propping is needed when the beam span exceeds the deck's unpropped spanning capability. For TR60 deck at 0.9mm gauge, the maximum unpropped span is about 3.6m; for TR80, about 4.2m. Propping consists of temporary Acrow props supporting the deck until the concrete has cured to at least 75% of its design strength (typically 7 days).

What mesh reinforcement is needed in composite slabs?

Anti-crack mesh (typically A142 or A193) is placed in the top of the slab to control shrinkage cracking. A142 (6mm bars at 200mm centres) is standard for most office and commercial floors. A193 (7mm bars at 200mm centres) is used for heavier loads or longer spans. The mesh should have 20mm minimum cover to the top surface.

TradeCalculator.co.uk

Metal Decking Calculator — Profile, Studs & Concrete Topping

Calculate composite metal decking requirements: profile selection by span, concrete topping depth, shear stud spacing, and mesh reinforcement for composite floor slabs.

Beam Span

Secondary beam span (deck span direction)

Floor Area

Total floor area to be decked

Deck ProfileProfile depth based on deck span

Imposed Load

3.5 kN/m² office, 5.0 kN/m² retail

How We Calculate This

This calculator determines the composite metal decking specification for a steel-framed floor, including deck profile, concrete volume, mesh reinforcement, and shear studs.