Raised access floors

Specifications

For many years, the primary specification for raised access floors was the PSA MOB (Method of Building) Standard PF2147. First published in 1982 it was subsequently amended and re-released in conjunction with the Access Flooring Association in 1992. It set basic performance criteria for various types of floor and gave 4 different grades of floor according to specific end use. The standard was onerous and exacting in terms of installation and tolerances, although some manufacturers claimed that it resulted in floor systems that were over-engineered. Floors designed to the MOB standard required independent testing.

Latterly, specifiers have been able to select raised floors according to BS EN 12825148, which published in 2001. This gives a greater range of options but differs from the MOB standard in a number of important respects; for example, floors designed to BS EN 12825 do not require independent testing and there are no specified tests for humidity and temperature effects on chipboard cores. Some manufacturers offer products complying with either standard.

The two documents are similar in some respects, but while there are only 4 grades under the MOB guide (PSA MOB PF2 PS/SPU, see the first table) there are theoretically 72 different possible combinations of performance standard under the European standard (BS EN 12825), see the second table ). Technically therefore, the risk of making an incorrect specification choice under BS EN 12825 is much greater. Furthermore, the two documents do not interrelate.

Features of a raised access floor specified to PSA MOB PF2 PS/SPU 1992

Grade and identification colour Use Uniformly distributed loading
Light General office accommodation without heavy equipment Not less than 6.7kN/m2
Medium General office accommodation where it is expected that heavy office equipment will be in use, data preparation rooms, educational accommodation and public areas Not less than 8kN/m2
Heavy Computer rooms, telephone exchanges, public areas and control rooms Not less than 2kN/m2
Extra heavy Computer rooms with heavy equipment and other special uses Not less than 2kN/m2

Possible combinations of panel specification under BS EN 12825:2001

Class of element Ultimate load at the point of failure Classes of deflection Classes of safety factor Classes of panel deviation in size
1 ¡Ý 4kN A, B or C, i.e. deflection of 2.5mm, 3mm or 4mm respectively Class 2 or Class 3 (take ultimate load and divide by safety factor to give working load) Class 1 and Class 2 (different allowances for thickness, dimensions, etc. with Class 1 being more onerous)
2 ¡Ý 6kN
3 ¡Ý 8kN
4 ¡Ý 9kN
5 ¡Ý 10kN
6 ¡Ý 12kN