How often do we hear about “prefab”: prefab houses, prefab offices, prefab boxes, but also roads, bridges, sheds?
The mode of prefabrication is quite varied, and the differences are not only given by the type or purpose of the artifacts but also by the starting materials.
What are the main types of prefabrication?
The large family of precast can be divided into three major categories: concrete or agglomerate precast, wood precast, and metal precast.
For all of them, the starting point is always the same and originates from the very concept of prefabrication: pre-assembling individual elements in the factory, as finished as possible, which then only have to be assembled and finished at their destination, with great advantages in terms of time and, therefore, economics.
Precast concrete products, which include not only structural elements (piers, beams, lintels, load-bearing elements) but increasingly also exterior and interior elements, are mostly used for large areas-typical the case of industrial plants-and for infrastructure.
Also well known are wood prefabs, which take advantage of the ease of processing the raw material. In Europe this type of product finds use mainly for small structures normally of service such as warehouses, shelters or temporary realizations. In contrast, in the Anglo-Saxon and especially American world this type of construction technique, also due to different cultural legacies, is also widely used in civil and residential construction.
Finally, there are metal prefabs, where the entire structure is built of metal: mainly iron and steel. And if in the beginning metal boxes and prefabs involved the use of simple sheet metal, today, thanks to development, the main element of metal prefabs is the sandwich panel, so called because, just like a sandwich, it is composed of two layers of sheet metal that enclose within them a layer of insulating material-typically polyurethane or mineral wool-which in addition to increasing insulation with the outside gives structure and solidity.
What are the special features of metal prefabs?
The basic philosophy is always the same, but prefabs and metal boxes can be very different depending on their use, where they are to be used and what they are to contain.
An extremely important variable is the thickness of the panels, which can vary from a few tens of millimeters to several centimeters, providing insulations from the external environment that are also important. The material from which the panels are made also changes their characteristics, both in terms of thermal and fire resistance.
Externally, it is possible to create a multiplicity of shapes and surfaces, thanks to the use of special profiles, the extreme adaptability of the panels, which can include openings, doors and hatches, windows and all kinds of finishes, and the possibility of joining or composing several metal prefabs to create even complex structures suitable for any use.
Internally, too, each metal prefabricated unit can be developed as desired, adding or removing walls, fixtures, and fittings, so as to obtain spaces that completely meet requirements.
As needed, then, all metal prefabs can be completed with electrical system, water system, toilets and heating/air conditioning.
What are the main uses of metal precast?
With prefabricated metal technology, a multitude of structures can be built both for the civil sphere – such as housing modules, schools, prefabricated offices, canteens, kitchens, changing rooms – and for the social and third sector (recreational venues, places of worship, gyms, sports venues). Not forgetting facilities for industry and shipbuilding such as field workshops, work camps, prefabricated housing, construction site facilities.
Finally, a particularly interesting application of metal prefabs is that of prefabricated bathrooms, single and also in batteries, with different possible configurations to meet all kinds of needs.
What regulations must a metal prefab comply with?
Like all prefabricated structures, metal boxes and prefabs must meet the requirements of current regulations, which vary according to where they are installed and their different uses.
For example, a metal prefabricated building intended for mountain areas (where significant snow loads are to be expected) will certainly have different structural characteristics than one intended for lowland or marine areas.
Another important variable in terms of the requirements that any metal prefab must meet is the intended use, because different will be the characteristics for prefabricated housing modules or offices than for prefabricated warehouses or metal boxes.
Among the particularities that may vary are, for example, surfaces, required by hygiene regulations, local regulations and safety laws if the structures are intended as workplaces. Other particularities that may vary include fire resistance (according to the various applicable technical regulations) or thermal systems and insulation (ex Law 10, for the Containment of Energy Consumption, and safety in the workplace).
