31 October 2017

What is a raised access floor?

A raised access floor system consists of load-bearing floor panels that are laid in a horizontal grid supported by adjustable vertical pedestals. As well as raising the level of the floor this creates a void that can be used for the housing and distribution of services with the panels being easily removable to allow access.

What's the history of raised access floors?

Raised access floors came to prominence in the 1960s and 70s as a way of servicing the IBM computers that were increasingly being installed in office environments. The BBC also made use of such floors to distribute services around offices and studios. By the 1980s office managers wanted more flexibility around working environments and cubicles gave way to open plan offices, requiring greater flexibility and raised access floors met the need to bring power and data up through the floor. In many respects little has changed since the 1980s although what can be found within the void probably has - with increasing requirements for heating, ventilation, data etc.

How is a raised access floor constructed?

Floor panels 

Floor panels are typically 600 x 600mm square and are available in various thicknesses, from around 25mm to 40mm. Thicker panels generally have a denser core and are designed to cope with heavier loadings. Panels are typically steel-encased woodcore or steel shell with a foamed cement-based core; the latter providing excellent structural and fire performance.


Pedestals are available in a range of heights and this variety is particularly useful on refurb projects where you may wish to raise floors above established features or where you need to create deep inspection chambers.

The pedestals are usually bonded to the sub floor using an epoxy resin-based adhesive with mechanical fixings also available if required. The pedestal provides vertical adjustment of around 40mm to allow the floor to be installed flat regardless of any variations in the sub-floor. The pedestal head provides panel location and (where required) a means of fixing the panel to the pedestal head. 

How are floors secured?

Loose-lay or gravity-held systems see floor panels resting on the pedestal head. The panels are held in place by their weight and allow quick and easy access to the floor void.

Lock or screw-down systems see the floor panels screwed or locked into position directly on the pedestal head. This kind of fixing is typically used when overlaying a floor covering - perhaps a vinyl or stone, to ensure there is no movement in the panel.

Steel bar stringers connect to the head of each pedestal to serve as a horizontal connector, usually at a height of around 600mm, providing greater lateral support and increasing the structural performance of the raised floor system. Stringers are available to cope with heavier loadings - perhaps when constructing a server room - and these will typically be made of denser steel.

A raised access floor used on the Old Post Office refurbishment project - home to NBS.

What are the typical applications of a raised floor solution?

Raised floors are common in applications where a range of building services are required. A raised access floor can be used to conceal services around electrical power, data, telecoms, air conditioning or environmental control, fire detection and suppression, water and drainage or security.

They are commonly seen in office environments that rely on significant levels of computer/telecoms equipment such as financial centres, government offices and call centres. Raised floors are also employed in data processing / telecom centres.

What are the advantages of a raised access floor?

One of the key advantages of a raised access flooring system is the quick and easy access to the components that lie beneath allowing for maintenance or re-configuration.

In a modern office environment the layout of partitioned rooms and individual desks can be expected to meet ever-changing requirements - perhaps adjusting spaces to accommodate new people or technologies, or meet the needs of new tenants.

A raised floor provides easy access to the services needed to meet these needs with as little disruption as possible.

What do you need to be mindful of when raising a floor?

In raising the floor existing skirting, plug and networking sockets and features like door and window frames may all need to be adapted to meet the new level of your floor.

Loading requirements also need to be taken into consideration - which areas of your space will see static traffic, which areas will be more dynamic?

When planning an installation, existing columns and curves can be accommodated but are typically cut out on site to ensure an accurate fit. This can add time to your installation schedule. Floor boxes are also typically added on site although, if placement is known in advance, manufacturers can pre-cut these on order reducing waste on-site and reducing time taken for installation and potentially cost too.

What are the alternatives to a raised access floor?

  • Suspended ceilings allow for trunking to be run at high level above the ceiling and for drop-downs to be provided at required locations via service poles. Relocation or maintenance needs to take place at height so the potential disruption in routing services through the ceiling is significant.
  • Pre-cast trunking
  • Skirting and dado trunking

Image: Seeweb - Posa dei cavi elettrici - CC-BY-SA 2.0