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Maximising Metal Decking Formwork: Key Design Considerations for Enhanced Safety and Performance

Metal decking formwork is widely used in modern construction for its versatility from civil applications and sacrificial formwork to concrete slabs with full composite action.

The best use of metal decking formwork is for composition applications where it brings significant structural efficiencies to the build. The integration of the metal decking formwork with the concrete and other steel elements forms a composite system that supports heavy loads and enhances structural integrity.

Whilst it’s crucial for a product to be certified and compliant with relevant building codes, it’s equally important to have a comprehensive understanding of composite action to realise the full potential of metal decking formwork.

Here’s some of the design considerations for composite slabs.

Load Capacity.

The load capacity determines its ability to safely support the anticipated weight throughout its service life without experiencing structural failure.

The load capacity hinges on many factors, including:

  • Steel Strength.
    The strength of the steel the metal decking is manufactured from is a primary factor in its load bearing capacity. High-tensile steel is often used for metal decking formwork, especially for composite slabs, for its increased load bearing capabilities.
  • Decking Profile.
    Different profiles of metal decking formwork perform differently and directly impact the load-carrying capacity too. Metal decking profiles that have deeper ribs typically offer greater strength and stiffness enabling them to support heavier loads.
  • Structural Layout.
    The spacing and configuration of the supports like the beams and joists also directly impacts the load capabilities. It’s essential to have adequate support to distribute the loads evenly to minimise deflection.
  • Connection Methods.
    The way the decking ties into the supporting structure also affects the load capacity. Properly designed and installed connections offer greater structural stability and integrity under load.


Engineers meticulously calculate the load capacities based on these factors to ensure the composite slabs can withstand the anticipated construction loads, live loads, and environmental loads. By accurately assessing load capacities, designers can create structurally sound and resilient buildings that meet performance requirements and regulatory standards.


The span refers to the distance between the supports that the metal decking formwork is installed on. It’s a key factor that impacts the structure’s strength and stability.

Longer spans cover more distance but need a heavier gauge steel, whereas a shorter span covers less distance and therefore can use lighter metal decking materials.

To design the most efficient structure would be to find the perfect balance between the two. If the spans are too long, you’ll pay more for heavy gauge materials and if they’re too short you might end up using more supports and increasing labour costs.

Fire Resistance.

Fire resistance in construction materials is non-negotiable, especially for metal decking formwork. In the event of a fire, the metal decking acts in holding up the structure to prevent collapse.

There are fire-resistant coatings that can be applied to the decking surface to help it withstand the heat and slow down the spread of the fire.

Many products, including metal decking formwork, undergo comprehensive fire testing to ensure they meet the strict fire resistance standards. The fire ratings ensure that the products can withstand specific fire conditions for a set amount of time.

When construction professionals focus on the right design considerations, they can make the most out of metal decking formwork and boost safety, durability and performance in their construction projects.

BlueDeck Composite™ by FTI Group.

The FTI BlueDeck Composite™ metal decking system has achieved complete compliance, providing users with a sense of confidence and assurance. BlueDeck Composite™’s adherence to the following standards has been confirmed as compliant.

• AS/NZS2327 for Comprehensive Composite Action
• AS/NZS1397 for Metallic Coated Steel Products
• Fire Rating to AS/NZS1530

The BlueDeck Composite™ Design Guide also outlines formwork design, composite slab design and fire design with all relevant detailing needed to design a more efficient structure. Download your copy here.

For further information on BlueDeck Composite™, you can get in touch with FTI Group at 1300 751 701 or explore their website at ftigroup.com.au.

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You can trust Fast Tread®
to be compliant with:

• AS/NZS1657:2018
for fixed platforms, walkways, stairways, and ladders
• AS/NZS1428.1:2009
for design for access and mobility
• AS/NZS1170.1:2002
for structural design actions
• AS/NZS3990:1993
for mechanical equipment
• AS/NZS4100:1998
for steel structures
• AS/NZS4991:2004
for lifting devices
• AS/NZS1554.1:2011
for structural steel welding
• AS/NZS4761:2001
for steel reinforcing materials

Compliance assured for your peace of mind. For more information, contact our design team.