Frequently Asked Questions

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Q. How are the anticipated loadings on the raised floor determined?
A. All test criteria for raised access floors measure the load on the floor surface measured in kilo Newtons (kN). Consequently the weight of any equipment that is to go onto the raised access floor needs to be converted into kilo Newtons

For example. A piece of equipment has a weight of 500 kilogrammes, what load will it impose on the floor? 1 kg imposes a load or force of 9.81 Newtons due to the gravitational pull of the earth. Therefore a weight of 500 kgs will impose a load on the floor of

500 x 9.81 = 4905 Newtons
1kN =1000 Newtons therefore 4905 Newtons
is expressed as 4.905kN

We now know that this piece of equipment is going to impose a load on the floor of 4.905kN.

However the next issue that must be considered is what area this load going to be spread over. This is a crucial aspect that has significant implications as shown below.

Firstly let us assume that the piece of equipment is 1200mm wide and 800mm deep. It has a flat base over which the weight will be spread. Therefore the load of 4.905kN will be distributed over the area of the equipment base that is

1.2m x 0.8m = 0.96m2

This piece of equipment will impose a uniformly distributed load of 4.905 kN over an area of 0.96m2.

This equates to 4.905kN / 0.96m2 = 5.11kN / m2

A uniformly distributed load of 5.11kN/m2 is within working loads of both light grade and medium grade requirements of the PSA MOB PF2 PS/SPU specification.

However let us consider the situation where the 4.905kN load is imposed on the floor through an area of 300mm x 300mm. This scenario imposes a concentrated load on the floor that surpasses the working concentrated loads of a medium grade floor, which is a load of 4.5 kN over an area of 300mm x 300mm. Consequently under these load conditions a heavy grade floor would be required. This example clearly shows how two significantly different conclusions can be got from the same initial basic piece of information i.e. this equipment weighs 500 kg, what grade of raised access floor do I need?

It is very important that all criteria relating to heavy equipment are obtained before any decision is made as to a raised floor specification.

A further aspect that must be considered with respect to the 500kg piece of equipment is how it is going to be moved into the building and how it is going to be moved across the raised floor. It may be the case that supplementary support is required to specific areas of
the raised floor and/or spreader plates are required on the raised floor surface whilst the equipment is moved into place. If in doubt ask!

Rolling loads need to be considered in situations where the raised floor will be subjected to frequent and repetitive vehicular traffic comprising of heavy equipment imposing high loads on the floor through a small number of wheels. High rolling loads repeated many times over a raised access floor will impose very high loads and stresses within the raised floor.

Consequently the Technical Department must be consulted in order to determine the optimum solution to a given set of circumstances.

Q. What structural grades of raised access floor are available?
A. BS EN 12825 allows specifiers to specify raised access flooring based upon selection by 6 classes of ultimate load ranging from 4kN to in excess of 12kN. In addition there is the selection of 2 safety factors and 3 maximum panel deflections under working load conditions. In order to carry out a meaningful assessment of the requirements of a raised floor system a full assessment of the anticipated loadings on the raised floor throughout its life cycle is essential. The PSA MOB PF2 PS/SPU specification outlines four grades of raised access flooring: light, medium, heavy and extra heavy. In addition it identifies which grade of floor should be used for specific application areas, e.g. medium grade for general office areas.