Composite Slab Cantilevers

Safety over performance

Maximum slab cantilevers are not entirely based on the performance of the deck or slab.  The figures are based on the safe distance of an arm extended through the edge protection system (assumed to be located on the edge beam top flange) avoiding the risk of working unsafely beyond the edge protection.


This rule is, however, this is subject to the type of edge protection system being used.


When designing cantilevers, the following should be noted;

  • A maximum cantilever length of 450mm (from toe of beam) can be safely installed when the deck spans perpendicular to the support.
  • For cantilevers greater than 450mm, suitable edge protection positioned outside of the slab edge position should be provided to allow safe installation. Please contact the SMD Technical Team as temporary propping may also be required.
  • Decking cannot be cantilevered where the sheet spans parallel to the supporting beam.

Edge trim may be suitable to achieve the desired detail (Refer Fig.4.7b);

  • Cantilevers should be designed and detailed as RC sections by the Structural Engineer
  • Cantilevers in the steel deck cannot be achieved where beams are pre-studded
  • For all cantilevers, the deck and/or trim acts as permanent formwork and not tensile reinforcement

VoidSafe, an alternative void solution

VoidSafe™ Protection System can significantly improve site logistics and access throughout the floor area.

For more information on this topic, see TGN Sections 4.7 and 4.8 specifically relating to this topic.

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By Thomas Rigden GMICE

SMD Technical Design Engineer

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