The concept is actually quite old. By using forming systems, engineers have decreased the weight of floor slabs by creating voids through a variety of techniques for a very long time. But newer systems now make it possible to increase the efficiency of cast-in-place (CIP) concrete construction and reduce overall cost.

Traditional voided-slab forming systems that have been used include waffle slabs, single-direction and double-direction span forming systems, and hollow-core precast slabs. The guiding principle, is that building owners and designers can get the advantages of a thin two-way-spanning flat-plate structure while the structural engineer can lighten the floor by more efficiently using the concrete.


Puffer Units – Void Slab System is used in all applications that require a structural plate together with the need to use less concrete and therefore for a lighter structure.

Puffer Units – Void Slab System is the ideal solution for creating slabs with a large span and/or great load-bearing capacity: it is particularly suited for structures that require considerable open spaces, such as executive, commercial and industrial buildings as well as public, civil and residential structures.It makes it possible to more irregularly distribute the columns, as beams do not need to be created. In the case of yards that are difficult to access or restructuring work, Puffer Units – Void Slab System, due to its stackability, modularity, lightness and maneuverability, can be used to make horizontal structures without the help of handling and hoisting equipment.


We are incorrectly led to estimate the advantage of a slab made lighter with Puffer Units – Void Slab System limiting it to a mere comparison between savings in concrete and the cost of the formwork on the level of the slabs only.

In this way however, as the analysis is immediate and intuitive, it does not account for the various economic, practical and operational advantages provided with Puffer Units – Void Slab System for the entire structure:

  • Less use of reinforcement in the slabs, columns and foundation up to a total of 15% (also in the case of variants)
  • Less concrete is used not only for the slabs but also for the columns and foundations
  • There are seismic advantages related to reduced building weight
  • Slimmer columns and foundations, lower costs related to excavation for foundations
  • Incorporates irregular arrangement of the columns to reflect the architectural freedom of the structure

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