What is a raised access floor?
A raised access floor, also called a computer floor, is a demountable floor that sits some distance above the structural floor. It consists of loose panels or tiles laid in a grid on adjustable supports (pedestals). In Dutch it is called a verhoogde vloer. The void between the structural floor and the raised floor is called the plenum, just like the space above a dropped ceiling.
What is a raised access floor for?
- Concealing services: electrics, data, cooling and heating run beneath the floor instead of through the room.
- Access: you lift a panel out with a suction lifter and can reach the cables straight away. This lets you move workstations and equipment without breaking anything open.
- Air distribution: in server rooms and data centres, cool air is blown through the plenum and perforated panels exactly where the heat is produced.
- Levelling height differences: because the pedestals are adjustable, the subfloor does not need to be flat. Useful in renovation and conversion projects.
Build-up
A raised access floor consists of pedestals glued or screwed to the structural floor, sometimes with connecting rails (stringers) between them, and panels made of, for example, calcium sulphate, chipboard or steel. The panels are often 600 x 600 mm and can be finished with carpet, vinyl or another top layer. It is a dry floor: there is no drying time as with a screed.
Application
You see raised access floors in offices, server rooms, control rooms, laboratories, cleanrooms and plant rooms. In homes, a similar solution is sometimes used to conceal pipes or raise a bathroom floor, although that is usually called a floating or raised timber floor.
Tips and points of attention
- Check the load capacity: choose panels and pedestals for the load of heavy cabinets or equipment, not just for foot traffic.
- Fire safety: if the plenum runs beneath a fire-resisting or smoke-resisting wall, that separation must also be continued within the plenum.
- Allow for the height: the floor uses up building height. Work with the clear height that remains afterwards.
- Earthing: with computer floors, the pedestals are often earthed to discharge static electricity.
Related terms
- Plenum
- Suspended ceiling system
- Screed
- ESD floor
- Dropped ceiling
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