Gulf Construction Online - Raised access floors uncovered

Ceilings, Floors & Partitions

Raised access floors uncovered

To many architects and designers today a world without raised access floors would be like a major office development without an elevator or an atrium, Kingspan Access floors charts out the development of raised access floors across the years.

01 February 2006

Raised access floor systems, which give maximum flexibility for the installation of a myriad of services to equipment and workstations, have gained such popularity over the years that they are being specified in every new headquarters building being built in the UK and also on many refurbishments of older structures.

Conceived in the early 1960s, when huge mainframe computers were created, access flooring allowed extensive cabling to provide incoming electrical supplies/signal wires (both in and out) plus ventilation to provide conditioned air to protect internal switchgear.
The first raised floors were very simple structures, consisting of timber sheets supported on timber joists or similar materials, but this type of construction was both structurally unsound and offered no method of access into the void. Gradually, it progressed into full access raised flooring using square panels made of plywood or chipboard.
In the late 1970s discussions with designers revealed a catalogue of problems that had occurred with raised access floors, including instantaneous or progressive collapse, and it was concluded that most of them could have been eliminated if these products had been manufactured and installed in accordance with a recognised performance specification, with each system being subjected to a rigid test regime and appropriate quality control procedures.

The Big Bang
In the late 1980s, the Big Bang (electronic data and information transfer, desk to desk) occurred which demanded numerous work stations to have desk-mounted PCs and telephones that all called for power supplies plus data and voice cables at a level never previously seen.
Raised access floors now became more sophisticated as they incorporated understructure able to cope with the demands of the construction industry – was able to be adjustable and lockable to specific heights and levels.
Despite all of this experience and professional development, the raised floor was still being installed on a concrete slab, which was first levelled and finished, sometimes with a screeds or similar, therefore the installation/construction programmes/periods remained relatively slow.
It should be noted that before raised floors, the method of construction was to simply lay a concrete slab, apply a sand cement screed, allow this to fully cure and then install broadloom carpet.

Programme issues
As raised flooring systems became more sophisticated, it became clear that there was no longer any need to lay a sand-cement screed as the final finish ready to receive soft finishes/carpets had actually become a totally flat and level surface, that is the top of a raised access floor.
These developments came at the beginning of the fast-track construction management revolution and from this point it was a very simple exercise to demonstrate that:
•  Casting and curing of the concrete slab: did not offer the possibility to change;
•  Application of a wet sand / cement screed: Across an average area, this might involve one week’s time to install and at least one further week to cure;
•  Installation of a raised access floor: required not more than three to four days for a similar area.
These very basic studies proved that the use of a raised access floor not only provided a cable management system and a flat and level platform for carpets but could also reduce construction programmes by at least two weeks per floor (that is, the period required to lay and cure a wet sand cement screed).
Where the raised access floor incorporated a carpet, this was shown to also save the period normally set aside to separately apply a carpet.
In addition to these straightforward issues we must also consider the additional weight that must be taken into account where sand/cement screeds are used with subfloor trunking systems rather than raised floors.

Fast track
The professional teams, who had cut their teeth on mainframe computer rooms, began to ask the question “why can’t we lay some of the basic service runs across a clear and uninterrupted concrete slab to speed up the delivery of the final building?” The simple answer given was that by adopting a different programming sequence, the electrical services would become damaged by the other trade contractors dragging mobile towers across the services to erect suspended ceilings etc.
The professional teams then concluded that if the basic service runs were installed first and then the raised access floors were laid, the other trade contractors could use the raised floor as a working platform whilst the same raised access floor could act as a form of services protection.
Adoption of this sequence again provided time-scale advantages in handing over a completed building in reduced periods, without the need for expensive protection systems.

Further ventures
The traditional method of introducing conditioned air into the office environment was to pass air through ducts installed through the suspended ceiling and down through grilles into the working space. However, as basic physics demonstrates, warm air rises and therefore it is necessary to force the air down from the ceiling – which is less economical than to allow the conditioned air to rise from a low-level distribution system
Again, the professional teams reviewed how they had taken air to mainframe computers and they began to design systems that either installed ductwork within the raised floor void or, more recently, used the actual raised floor as a plenum. The latter option shows considerable initial cost savings over the alternative option as the ductwork itself is eliminated. These systems not only provide environmental advantages from the reduced energy costs but they also allow the air to be delivered to exactly the location needed, for example computers, windows (to reduce condensation), people etc.

Churn rates
The initial costs of a raised floor, especially if programme advantages are ignored, are higher than those with a building with screeds and perimeter cable management systems etc.
However, with the modern style of office development based around open plan offices with workstations, there are high turn rates – constant changes in desk layout and services, which require the initial cable management design to be substantially modified on a regular basis Churn.
Every time these cable management systems need to be modified, the raised floor option offers considerable “churn” cost savings.
• To alter or amend the services with a raised floor requires the simple lifting of a panel, introduction of new cables and then the replacement of the same panel.
• With traditional cable management systems, such as subfloor trunking, it is necessary to either scabble the concrete slab and introduce a new piece of trunking before making good the slab. The alternative is to run the cables over the surface of the floor, which can result in trip hazards and also possible damage to the cables themselves (this can cause equipment failure and even electrical shocks!)