Specifications

The Property Services Agency (PSA) Method of Building Performance Specification 'Platform Floors (Raised Access Floors)', MOB PF2 PF2 PS, became the de facto industry standard in the UK for about 20 years until the recent arrival of the BS EN 12825:2001 specification. It consists of performance requirements verifiable by standard testing procedures. Requirements covered include dimensional accuracy, moisture and thermal movement, strength grades, fire safety, floor panel finishes and electrical bonding and continuity. The last edition (March 1992) of the MOB PF2 PS was given the suffix SPU (single project use). It was produced in conjunction with the Access Flooring Association (AFA) and includes changes that affect nomenclature making it more relevant for non-government contracts; the performance requirements and test methods remain unchanged.

The table below shows the structural performance of each of the four grades of raised access floor outlined by this specification along with typical areas of application.

Table 1: MOB PF2 PS/SPU Structural grades and typical uses

In July 2001 a European Standard EN 12825 was approved by CEN as a voluntary specification for private projects and mandatory for public projects. It is anticipated that this standard will become mandatory for all projects across the member states of the EU within 5 years of approval. This specification outlines classifications for raised access floor systems based on their ultimate load; this is the load at which failure occurs. The raised access floor system is tested to its ultimate load under the application of a 25mm x 25mm point load at a predetermined rate until failure occurs. During the application of this load the deflection of the floor panel is measured to produce a graph of applied load against deflection. This information is then used to determine the classification of the floor system. Raised floor systems are classified in terms of ultimate load, safety factor, deflection under working load and dimensional tolerances.

The classification system allows for six classes of ultimate load ranging from greater than 4kN to greater than 12kN. Against each of these six ultimate loads there is a choice of a safety factor of 3 or 2. Further for each of these ultimate load and safety factors three maximum deflections under working load conditions are available namely 2.5mm, 3.0mm and 4mm.

What BS EN 12825 does not intend to do is interpret the classifications or advise which class of raised access floor would be suitable for a specific application. The product application chart shown below gives guidance as to product classification against specific areas of application. These classifications are based upon the ultimate load determined in the manner prescribed within BS EN 12825. Further these classifications are based on a 2.5mm deflection under working load conditions and a safety factor of 3 which, in the opinion of Kingspan Access Floors are best suited for most applications when taking due regard for the UK construction industry and the expectations of raised access flooring with regard to panel deflection etc.

Therefore a typical classification might be outlined as 3/A/3/2 where;-

• 3 is the ultimate load class in excess of 8kN
• A is the deflection under instantaneous working load of less than 2.5mm
• 3 is the safety factor
• 2 is the dimensional tolerances classification 

Proposed BS EN 12825 classifications suited to application areas

This chart shows that the BS EN 12825 offers increased flexibility to the specifier in that application areas can be sub-divided into light, standard and heavy use with different classifications of product accordingly specified. The terms light, standard and heavy in relation to the application areas are an attempt to differentiate between the levels of use across any application area. Specific definitions are difficult to quantify but for general office might be as follows;

• Light, occupancy levels of 1 person/15m2 with one computer per desk, limited number of filing cabinets, small photocopiers etc. Office working hours limited to 9am - 5pm for 5 days per week
• Standard, occupancy levels of 1 person/12m2 with two computers per desk, filing cabinets, general photocopiers etc. Office working hours basically 10 -12 hours per day for 5 days per week.
• Heavy, occupancy levels of 1 person/8m2 with two or three computers per desk, filing cabinets, larger photocopiers etc. Office working hours may be extended up to 24 hours, 5 days per week