I voided slab

I voided slab

The I-voided biaxial slab system is created by using a recycled plastic formwork that was designed to lighten slabs and raft foundations. The I-void form has a box shape and it is elevated by the use of four conic feet. The formwork is not reusable and stays within the slab once cast with concrete.

The I-void form voids the middle of the slab section, it removes only the inefficient concrete. The concrete section becomes a grid of perpendicular I-section beams, with the compression and tension areas untouched. This results in considerable reduction of concrete (30 to 35%), while its inertia stays almost the same. The reduction in load leads to smaller deflections and less reinforcement.

The I-void slab can be reinforced with post tension tendons to provide the ultimate hybrid solution for towers and long spans slabs.


  • Heights of I-void form starts at 13cm all the way of to 40 cm.
  • The I-void forms are stackable on top of each other making it easy to store and handle.
  • They are made out of recycled plastic and designed to withstand 80 kg for labors to set on it.

Product use

  • Towers and high rise buildings of 15 floors and above. The reduction in weight becomes significant on the columns and foundations that leads to cost saving and optimization for the whole structure. Moreover, walls and columns will become smaller, giving more architectural space for each room.
  • Long spans: for spans of more than 10 meters. The longer the span, the thicker and heavier the slab becomes reducing in turn its capacity. The I-void form will lighten the slab and increase its capacity in long spans.
  • Lands with weak soil capacity, a reduction in load will lead to significant cost savings in foundations. In some cases, it will remove completely the need for piles and deep  foundations.


  • Large spans leading to architectural freedom.
  • Flat soffit of slab removes the need for gypsum board and false ceilings.
  • No drop beams are needed even for large spans.
  • Reduction in weight of slab and building.
  • Decrease in seismic forces acting on the building as it is directly proportional to its weight.
  • Smaller column sections and reinforcement.
  • Lower cost of foundations.
  • I -void forms are light, easy to position and to handle.
Quote your project