75 mm Floor Decking Sheets for Heavy-Duty Floor Systems

The key difference is structural depth: the 75MM profile provides a deeper rib geometry than the 50MM, which increases the composite slab's structural depth and its capacity to span longer distances between beams and carry higher imposed loads without propping. The 75MM profile is specified when: (a) structural bay spans exceed the efficient range of the 50MM profile — typically above 4.0–4.5 metres in standard configurations; (b) design imposed loads are elevated — industrial equipment platforms, transfer floors, plant room levels, or high-load storage decks; (c) the structural engineer requires additional composite slab depth to manage deflection under service loads; or (d) the project involves wide-bay construction where minimising the number of secondary beams is a structural and cost priority. For standard commercial office spans and loads, 50MM is typically sufficient; for anything heavier, longer, or more structurally demanding, 75MM is the correct specification.

Crop ends are short sections of decking, or structural details at the ends of deck spans, that are provided to absorb the negative bending moments that develop at the supports of a continuous composite slab. In a multi-span composite floor system, the slab spans between beams and the deck profile carries positive moment (tension at the bottom) in the midspan zone — which is where the deck's composite action is most effective. At the supports, however, the moment reverses — negative moment causes tension at the top of the slab — which must be resisted by top-face reinforcement or a structural detail at the beam. Crop ends address this by providing the correct structural transition at the support zone. The reference design specifies that appropriate crop ends must be provided to absorb these negative moments — and Alfaa PEB's technical guidance covers the correct crop end detailing for your specific structural configuration.

Load capacity depends on the sheet thickness, the concrete topping depth, the span between supporting beams, the slab reinforcement specification, and the crop end detailing — and is determined by the structural engineer for each specific project. As a project planning reference: 75MM composite decks in standard configurations typically achieve imposed load capacities from 5.0 kN/m² for standard commercial applications up to 10–15 kN/m² or higher for heavy industrial, plant room, and high-load storage applications, with unpropped spans typically ranging from 3.0 to 6.0 metres depending on sheet thickness and slab depth. The 75MM profile extends the practical span and load range significantly beyond the 50MM system — and Alfaa PEB supplies sheets to the structural engineer's specification for any design load and span combination.

75MM Flordec sheets are manufactured from hot-dip galvanised or PPGI (prepainted galvanised) steel, providing corrosion protection on both the exposed soffit face and the top surface in contact with wet concrete during Stage 1 construction. The galvanised or PPGI coating protects the deck throughout site exposure, handling, and the construction phase. Once the composite slab is complete, the permanently exposed soffit continues to be protected by the coating for the full service life of the building — requiring no maintenance in standard internal environments. PPGI is specified where an enhanced soffit finish appearance is required, where the service environment warrants additional surface protection, or where a colour-coordinated ceiling soffit is part of the architectural specification. Both options are available from Alfaa PEB to project specification.