COBIAX | Voided can do more

Voided can do more

Solid slabs have a flaw: They are extremely heavy. This extreme weight not only puts strain on the slab itself! It also exerts a great burden on the foundations and the framework of the building.

The X-Zone: the Cobiax secret for maximum load-bearing ability at the lowest weight 

Coca-Cola has its secret formula. Cobiax has its X-Zone: the weight-bearing area between the individual Cobiax void formers. This area is crucial in terms of how much weight the slab can carry. 

At the end of the 20th century most of the weight-bearing structures in the first voided flat slabs had a rectangular shape – long “tubes” inside the block of concrete or even cubical elements. The weak point of these types of construction is still the continuous narrow web, which usually means that additional reinforcement is needed to cope with the shearing forces.

Above: Clearly visible X-Zone on a Cobiax CLS structural former. Below: After extraction of a structural former from a CLS test.

Left: Clearly visible X-Zone on a Cobiax CLS structural former. Right: After extraction of a structural former from a CLS test.

At the turn of the millennium, companies were working on ways to optimise the concrete structure remaining outside the void formers. The aim of void former technology was to manage without any additional reinforcement; Cobiax also carried out research that focused on creating the most ideal X-Zone possible. The solution was to move away from rectangular void formers and develop spherical or ellipsoid-shaped void formers, which formed a concrete structure with webs that widen out upwards and downwards so that they do not require additional reinforcement.

Cross section: The ribbed or cassette slab requires additional shear force reinforcement (red). The Cobiax slab with X-Zone (blue) does not.

Cross section: The ribbed or cassette slab requires additional shear force reinforcement (red). The Cobiax slab with X-Zone (blue) does not.

In the top view, it becomes almost even clearer how small-scaled and thus more complex a void former slab without the Cobiax X-Zone is.

In the top view, it becomes almost even clearer how small-scaled and thus more complex a void former slab without the Cobiax X-Zone is.

Over the decades, Cobiax has continued to optimise the shape of the structural formers to achieve the ideal concrete shape between the modules in terms of structural engineering. 

It is this X-shaped concrete structure that provides the unique stability and therefore safety of Cobiax voided flat slabs. No other void former element that does not have any additional reinforcement achieves such an optimised X-Zone as the Cobiax systems. 

All of the other optimisations in the product lines, such as the two-part design or the assembly-securing elements, are add-ons that have no effect on stability or weight reduction, but mainly provide economic benefits or make them easier to assemble. 

This means that the Cobiax void former systems are the only products on the market that combine the best possible load-bearing ability with maximum saving of resources and particularly economical assembly.

Cobiax technologies have the following approach: they reduce the weight and thickness of the slabs for certain constructions, or they enable larger areas to be spanned, at the same weight.

Although this principle of material reduction in statically unimportant areas of construction has been tried and tested for a long time, and is frequently used (e.g. steel beams and hollow slabs), predominantly, reinforced concrete slabs are still used. In buildings, most of the concrete is used in the slabs.

But the use of concrete, with its high consumption of resources, can be usefully optimised by the implementation of intelligent voided building methods; the Cobiax technology even offers a biaxial load-bearing effect.

The results of these considerations were the hour of birth for the Cobiax technology in 2004.

As a fully precast element, or assembled on site

Traditionally, Cobiax void formers are incorporated into the building process on the construction site (in-situ concrete), according to the construction requirements. But they can also be incorporated as industrially manufactured, fully precast elements, or in a combination with precast elements.

The voids in the concrete slab, which is to be cast later, are inserted in the form of void formers or structural formers, both made out of plastic. The concrete then flows into the correct static structure; the formers keep the voids open.

Maximum conservation of resources

This results in a high weight-bearing slab construction, that not only saves material (concrete), but also enables larger spaces to be spanned at the same weight.
A rough calculation already indicates how efficient building with Cobiax is: one truckload of preassembled Cobiax void formers basically replaces seven truckloads of concrete, and one load of unassembled Cobiax components replaces a whopping 25 truckloads of concrete.

Guaranteed construction design

Advances in building technology should never be at the expense of safety. That’s why many years of research went into the Cobiax technology which, meanwhile, has become an internationally accepted building method. So, construction companies, engineers, architects and builders can be assured that they will reap the benefits of the many advantages of Cobiax voided systems, without the slightest risk in terms of structural stability.


The Cobiax advantage

The Cobiax advantage for architects

Greater design freedom

Cobiax voided flat plate slab systems enable larger areas to be spanned, at the same weight. The architect is released from structural limitations and is able to plan more freely.

Slimmer slabs and walls

A building that is lighter and slimmer overall, can be planned. This not only results in pleasing aesthetics. It also reduces the amount of material required.

Fewer columns

Thanks to the limited weight of the Cobiax slabs, fewer columns are required; additional rooms, with all of the advantages of aesthetics and flexible use, are possible.


Building with Cobiax always means making a commitment to future-oriented solutions in the area of resource conservation and sustainability. Therefore, it is with good reason that buildings that contain Cobiax technologies have won international prizes. By planning with Cobiax, architects clearly underpin their innovativeness and their commitment to modern, contemporary building methods.


The Cobiax advantage

The Cobiax advantage for builders

Reduction of costs

Slabs, walls, columns and foundations can be optimised for the reduced load-bearing capacity – they are lighter and smaller, and therefore cheaper.

Faster construction

Beam solutions often require time-consuming intermediate steps during the building process. With Cobiax technologies, these beam constructions are no longer necessary – building time is reduced and the building can be put into operation sooner.

Considerably increased usability

Columns and beams limit the design possibilities for the entire space. They determine the division of the building into individual rooms or at least dictate the structure of the aesthetic impression. Cobiax technologies avoid these limitations – they enable wider scopes, which offer completely new opportunities for use, as required. In dynamic markets and social models, this flexibility offers considerable economic advantages.

Higher profitability

In many cases, the limited depth required for the slab, means that more storeys become possible. Furthermore, thanks to the thinner walls and the fact that no support columns are required, the usable space increases. All these advantages, added together, increase the profitability of the project considerably.

Social and political reputation

Building with Cobiax makes a substantial contribution towards reducing the CO2 balance of a building, beginning with the building process (up to 20%). The primary energy requirements are up to 22% below those for conventional solid slab building methods. All the Cobiax products consist of 100% recycled post-consumer plastic; even if the building is demolished, environment-friendly waste disposal is guaranteed. Therefore, Cobiax buildings regularly win international prizes for environment-conscious building.


The Cobiax advantage

The Cobiax advantage for engineers


It is decisively easier to keep structural records of the slab building elements and the building as a whole.

Shape Retention

Thanks to the reduced weight of the slabs, distortion of the ceilings themselves is reduced, and the building retains its shape better.

Slimmer building elements

The reduced load enables the use of more delicate, elegant building elements.

Less load for the foundation and the substructure

The limited thickness of the slabs is advantageous for the planning of the foundations and substructures: the foundations have to distribute reduced loads, and can therefore be made smaller; the substructure components can be reduced in size, or they can be omitted entirely (e.g. supporting columns)

Easier earthquake certification

With Cobiax voided flat plate slabs, earthquake certification is easier; the reduced (moving) load is dynamically more tolerant than a conventionally designed building.

Construction companies

The Cobiax advantage

The Cobiax advantage for construction companies

Shorter construction time

With Cobiax slabs, complicated beam solutions and pretensioning of ceilings isn’t necessary. This saves a substantial intermediate step in the construction phase; furthermore, scheduling is more reliable.

Less material required

The concrete required for the slabs is reduced by up to 35%; the material costs drop accordingly.

Simple handling

All of the Cobiax products are easy to lay; the Cobiax CLS technology considerably reduces the need for reinforcement.

Reduction of delivery traffic

Thanks to the reduced need for concrete, up to 35% less concrete delivery trucks are required. This not only facilitates the smooth running of the construction process. It also increases the level of acceptance of the building methods by neighbouring residents and institutions.


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Wider Scopes as an obligation
Cobiax is more than just a brand. The catch phrase “Wider Scopes” extends far beyond the possibilities for modern slab technology. It is a commitment to providing more room for play for people, in the scopes and spaces in which they live and work.
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