„TOP 4S“ is a disposable formwork made from recycled polypropylene suitable to create ventilated crawl spaces, cavities and floors in all types of new construction or renovation.

Features and Advantages

„TOP 4S“ an innovative system for building ventilated crawl spaces, floors and roofs and cavities in general. Is a square element 50 x 50 cm, equipped with a versatile joining system by which and element can be modularly overlapped to the next. In the heights H-35 H-40 H-45 H-50 H-55 there is a safety joint that prevents the legs from opening during casting.
On each module there are directional arrows and an assembly diagram showing the correct direction of installation.

With „TOP 4S“ a safe platform which can be walked on is created and over this the concrete is cast.

„TOP 4S“
is generally installed on a foundation of lean concrete of varying thickness depending on the situation. After the laying of a suitable mesh, proceeding with the casting of concrete, many pillars are formed which, once the concrete is cured, determine the actual resistance of the floor, with the uniform distribution of loads over the entire surface. TOP 4S  is used in new constructions or in renovations of residential and industrial buildings.

„TOP 4S“
creates a plumbing space with an appropriate steam barrier for the floor and, properly ventilated by pipes connected with the outside, a vehicle for the disposal of Radon gas.

„TOP 4S“
has a spherical shape, this feature allows the structure to work in an arc (single compression of the concrete), allowing maximum mechanical strength with minimum thickness of concrete, ensuring a considerable saving in materials. The spherical shape of the cap allows for the instant identification of the section of minimum thickness of concrete. In this way, at that section the necessary contraction joints can be made, with the absolute guarantee of control of shrinkage cracks.

TOP 4S is produced in the following sizes:

4,5-8-13-16-20-25-27-30-25-40-45-50-55cm  to meet diverse construction requirements.

  • Speed and simplicity of installation (one person can lay up to 100 square meters per hour)
  • It can be walked on during the work phase
  • Reduces labour time by 80%
  • Saves concrete
  • Adaptation for out of square areas by cutting the elements
  • Natural or forced ventilation across the whole surface
  • Passage of the systems under the floor in all directions
  • Ability to create the foundation beams and slab with a single casting using the FERMOplast or TELEstop accessories.
  • Crawl spaces, ventilated crawl spaces, cavities and floors in residential and industrial buildings which are under construction or being renovated
  • plumbing spaces
  • floating floors
  • urban redevelopment in general (pavements, squares, etc...)
  • sports centres
  • ecological systems and platforms
  • cold rooms, drying rooms, greenhouses, rooms at a constant temperature
  • underground channels
  • roof gardens

Radon Gas

GAS RADON is a radioactive gas, which is colourless and highly volatile, produced by some of the rocks of the earth’s crust and therefore present in different concentrations in all types of terrain. In areas where the ground is particularly rich in this element, closed environments can favour the build-up of high levels of radon which are dangerous to humans. The ventilated crawl space, allowing air flow under the building, allows the release and dispersion of GAS RADON into the atmosphere, thus avoiding it reaching the rooms which are lived in.

Laying method

The joining system of the TOP 4S allows it to be installed quickly and easily. Lay the elements from top to bottom and from left to right, ending one row at a time. The two arrows on each element should be directed upwards and to the right (see picture).

Execution of a ventilated crawl space
  • Preparation of the rolled gravel subbase.
  • Creation of the lean concrete subbase, of variable thickness depending on the overloads and the capacity of the ground.
  • Placement of the rebar for the foundation beams
  • Creation of ventilation holes (for correct functioning the creation of a 125 mm diameter hole every 3/4 ml is recommended, with low entry to the north and high exit to the south) and any placement of pipes.
  • Installation of the FERMOplast accessory (in the case of single casting of foundation beams and slab).
  • Installation of the recycled polypropylene disposable formworks.
  • Installation of the TELEstop accessory (in the case of single casting of foundation beams and slab and/or to avoid cutting the formworks).
  • Installation of electrowelded mesh.
  • Laying of the concrete to create a cap of variable thickness depending on the intended use of the work.
  • Vibration of the concrete layer.


Telestop is a modular system consisting of a stopper and a telescopic extension made of polypropylene that closes the formwork and allows the simultaneous laying of the slab and foundation beams thereby reducing costs. It can be used as a simple stopper or as an extension to avoid cutting the formwork, thereby reducing the laying time. Compared to similar products which are commercially available, it saves concrete, because the extension is the same height as the formwork to which it is coupled.
The telestop system is available for Vespaio 4S H-13 → H-55.


Is a polypropylene sheet that allows the closing of the formwork and enables the construction of the slab and foundation beams with a single laying of concrete (this product can also be used with MAGNUM). Quick and easy to lay, it can be cut with a normal cutter to fit it to the passage of tubes and systems.

Compared with ordinary procedures, it can reduce the foundation construction time by up to 80%.

Safety at work

TOP 4S has been tested at the University of Trieste. Various tests have been carried out including the puching resistance test, to ensure the capacity of the formwork and therefore the safety on site.

The Decree of the Ministry of Public Works of January 9, 1996, 7.2.4 - Resistance to punching says that: “In the absence of a continuous lower formwork during the phase of reinforcement and casting, blocks of any type must withstand a concentrated load, applied at the centre of the upper band of at least 1.5 kN (150 kg).”

Therefore a formwork must withstand a punching load of 150 kg, this is the minimum limit stipulated, because it corresponds to the weight of a person in motion above the formworks. Three punching tests were carried out and the results are as follows: