At present, the regulatory framework relating to the raised floor system is under discussion and approval at Uni. The standard document, currently under examination, starts from a document drawn up by Assofit (National Association of Technical Finishing Entrepreneurs) which formed the basis for the discussion of the work started at Uni by the GL13 working group of the SC4 Construction subcommittee, which represents the Italy in the Cen Technical Committee in charge of preparing the European standard on raised floors in accordance with the European Directive 89/106.
The work focuses in particular on the analysis of the fundamental requirements indicated by the European directive, determining the necessary characteristics and methodologies to verify them.
This legislation – applicable only to those flooring systems which, thanks to the removable panels, provide full access in any position – also represents a valid guide for those, designers and / or users, who are interested in the raised floor product.
For this reason we believe it is very useful to anticipate some contents of the standard, in particular those relating to the general parameters of mechanical resistance, electrical resistance, fire behavior and acoustic characteristics. In fact, the consideration of these parameters constitutes the first evaluation criterion to verify the reliability of the raised floor product.
General regulatory parameters
There are significant parameters for the choice of a raised floor which can be summarized in a series of requirements placed on the product by the market. Initially, the rules were dictated by the historical users of raised floors, ie companies in the information technology sector of American origin or large national bodies. To date, as the product is not recognized, the legislative arguments developed concern the construction field in general, including the EEC Directive 89/106 which indicates the essential requirements for construction products:
This value is measured and expressed exclusively by the resistance to the concentrated load. The resistance values are expressed as a function of an “arrow” and therefore of the bending that the technical floor undergoes under a certain load. The reference arrow is 2.5 mm (regardless of the type of construction material, a panel is accepted which, subjected to a certain load by means of a 25 mm square punch, does not have a deflection greater than this measure). It is also necessary to consider the concept of “stabilized” bending, ie the prolonged load resistance of the raised floor system in its complexity. It is also customary to express the safety factor 2, a parameter that serves to verify that the panel does not break when tested with a load equal to 2 times the load of normal use.
At European level, floors tend to be divided into four categories of capacity:
The progressive need to equip the tertiary office with electronic equipment requires, for their proper functioning and also for the safety of people, that the raised floor has an adequate level of electrical resistance. The values must be between 1.5 × 105 ohms and 2 × 1010 ohms on average. Within this delta, a raised floor can be considered antistatic. Floors intended for rooms other than EDCs may have slightly higher electrical resistances.
It must be considered that, regardless of the composition of the panel, the antistaticity of the raised floor is determined by the walking surface and therefore by the covering. Roofing materials with antistatic behavior include: linoleum, antistatic pvc, plastic laminates. The degree of electrical resistance of wood and stone, on the other hand, depends on the type of surface treatment. We mean conductive floors that have values from 1.5 × 105 up to 1.5 × 107 ohms. They have particular uses in environments with very sophisticated electronic equipment. To ensure conductivity, not only the coatings but also the structural core of the panels must be conductive. The core of the panel can be made either in a conductive wood conglomerate, for example with the addition of graphite, or in a wood conglomerate made conductive by a bridge that guarantees the passage of electrostatic charges from the top to the bottom of the panel. The same goes for inert materials.
Behavior to fire
This concept summarizes three fundamental requirements:
* fire resistant
* reaction to fire
* fire load.
The characteristic of fire resistance is evaluated on the basis of three parameters:
The tests and certifications indicate how many minutes the floor maintains its characteristics unaltered. The reaction to fire expresses the behavior of a raised floor subjected to an attempted ignition (ignition of a flame) from the outside. The lower the value – which is expressed in classes – the better the fire behavior of the material.
The problem of the fire load is not always studied in depth, which, on the other hand, is a fundamental and complex aspect, since the calculation of this value must take into account all the materials present in the environment. Over the years, the trend of a very high REi certification request has been valid; tendency derived from the behavior of designers to make requests that are oversized compared to real needs. Instead, currently, an attitude of critical revision of the concept of fire behavior prevails, no longer analyzed by individual components but according to an overall logic.
The specific legislation is being studied: for the moment we rely on the tests carried out in the related sectors (partition walls, roof coverings). From tests carried out in the specific sector, using different types of coatings and panels, it appears that the level of noise in the environment, mainly due to foot traffic, varies not so much according to the composition of the panel but rather according to the surface coating. The height of the structure also affects the transmission of noise in the environment, directly proportional to the internal subdivisions of the plenum, which is why the “rumble effect” remains mostly a prerogative of open spaces.
The floor subjected to foot traffic generates a more or less intense noise depending on:
In essence, the noise is related to the mass in an inversely proportional way, that is, the increase in the mass of the raised floor corresponds to a decrease in the noise caused. If, therefore, the need for acoustic comfort is the priority for the client, it may be a good rule to use a panel in inert mineral conglomerate. It is understood that this choice involves costs of a certain level and in any case a careful evaluation also of the covering finish.