A raised access floor comprises of load bearing floor panels laid in a horizontal grid supported by adjustable vertical pedestals to provide an under floor space for the housing and distribution of services. The floor panels are readily removable to allow quick access to the under floor services.Components of a Raised Access Floor System
The key components of a raised access flooring system can be defined as follows:Floor Panel
This is the horizontal load bearing component of a raised floor. It is normally 24"x 24" square (industry standard module size) but can be 24" metric square.These sizes are nominal sizes and clarification should be sought from the manufacturer as to their stated panel size and tolerances. These floor panels will be supplied as either bare finished to accept a carpet tile finish on site or, with a factory bonded finish.
Pedestal
This is the complete vertical, adjustable supporting structure to the raised floor panels. The pedestals are normally bonded to the sub floor using a epoxy resin based adhesive with mechanical fixings also provided if required. The pedestal assembly provides vertical adjustment of 1½" to allow the raised floor to be installed flat and level despite undulations in the sub floor. The pedestal head provides panel location and also when required a means of fixing the panel to the pedestal head.Stringer
This is a horizontal component that connects pedestals together. It connects to the pedestal head and is used to provide additional lateral support at greater floor height and/or increase the structural performance of the raised floor system.
What are the benefits of using a raised access floor?
Raised access floors are used extensively to provide the following benefits:
1. Quick and easy access to the ever increasing volume of power, data and
telecom services found within a modern building.
2. In speculative buildings premises need to be adaptable for the needs of incoming occupiers.
3. Once occupied offices need to cater for office Churn and lend themselves
to new office organizations and layouts with the redirection of services that implies.
4. Accessibility is a major consideration. People want easy access to the
services for maintenance, rerouting or upgrading with as little disruption as possible to the work process.
1. Quick and easy access to the ever increasing volume of power, data and
telecom services found within a modern building.
2. In speculative buildings premises need to be adaptable for the needs of incoming occupiers.
3. Once occupied offices need to cater for office Churn and lend themselves
to new office organizations and layouts with the redirection of services that implies.
4. Accessibility is a major consideration. People want easy access to the
services for maintenance, rerouting or upgrading with as little disruption as possible to the work process.
What types of raised access floor are available?
There are two basic groups of raised access floor system available each with their own advantages:
1. Gravity held or loose lay products.
Here the floor panels rest on the pedestal head. The panels are held in place by their weight with lateral location providing engagement between panel and pedestal head. These systems allow very quick and easy access to the floor void and the panels can be readily finished with factory bonded finishes.
2. Lock down or screw down products.
In this case the floor panel is screwed or locked directly to the pedestal head thereby holding the panel in place and also providing lateral location. This system provides a very solid and rock free floor with quick and easy access to the floor void. However these systems cannot accept factory bonded finishes.
What is the construction of a floor panel?
There are various basic floor panel constructions that are outlined below along with various attributes of each type.
Steel encased wood-core.
This panel construction comprises of a high density particle board core that is encased by galvanized steel laminated to the particle board by a structural polyurethane or epoxy resin adhesive. This construction type is capable of providing high strength and good fire and acoustic performance. By varying the thickness of the steel sheet and the strength of the chipboard core a wide range of structural performance is available.
Steel/cementitious panels.
Here a structural steel shell comprising of a flat steel top and a profiled steel base are welded together to form a hollow shell. This shell is then filled with a foamed cement based core to give a panel that gives good structural performance in conjunction with excellent fire performance. In certain cases the hollow unfilled steel shell will provide a floor panel that gives suitable structural performance although its acoustic performance is limited.
What are stringers and why use them?
Stringers are introduced for various reasons each with their own specific design.
Snap on stringers.
These snap onto the pedestal head and are used to provide additional lateral support to the raised floor. They are normally introduced at floor heights of 24" and above or for use with floor panels complete with factory bonded finishes. Snap on stringers are normally designed to increase the structural performance of the raised floor.
Bolt on stringers.
These are screwed into the pedestal head and are designed as structural components and as such increase the structural performance of the raised floor system. They will also provide increased lateral stability.
Air plenum stringers.
These stringers are designed only as a means of providing an air seal to the panel joints through the use of a gasket strip. They do not provide any increase to the lateral stability or structural performance of the floor.
Perimeter stringers.
These provide additional support to cut panels around the perimeters if required by the project specification
What is to be the use of the building in which the raised access floor is to be installed?
It is important that consideration is given to the intended use of the building as part of the evaluation process. Raised access floors are used in a wide range of buildings which includes the following:
- General modern offices, any office environment where there is a need for a significant level of computer/telecom equipment.
- Call Centers, office environment set up to handle large scale customer enquiries thereby requiring significant levels of computer/telecom equipment.
- Data processing centers. Large scale computer rooms set up for the processing of electronic data i.e. customer information, financial information etc.
- Telecom switch centers. Old mechanical telephone exchanges now replaced by electronic switch facilities. Also new mobile technology requires new electronic switch facilities.
- Distribution centers. These facilities distribute a vast range of fast moving consumer goods with order processing and such activities handled in a modern office environment.
- Educational facilities, raised flooring used in specific learning areas in schools, universities etc. Also used in library and major archive areas.
- Retail facilities such as major department stores increasingly using raised floors surfaced with special finishes.
The type of area in which the raised access floor will be used will help to define the structural performance required of the raised floor and also the specific type of finish required to the floor surface.
What level of services is anticipated under the raised access floor?
The anticipated use of the basic space in which the raised access floor is to be used will determine the projected level of power, data, telecom, HVAC (Heating, Ventilation and Air Condition) and other services that will be located under the raised access floor. This information can then be used to determine the cavity depth required under the raised floor and hence the finished floor height which will then be used in specifying the raised access floor system.
What are the anticipated structural requirements of the raised access flooring in terms of static loads, rolling loads and pedestrian traffic?
It is important at an early stage in the consideration of a raised access floor that a detailed assessment is made of the likely loadings that will be imposed on the floor surface. These loadings need to be assessed in terms of:
Static loads:
⦁ Uniformly distributed loads
⦁ Point loads
⦁ Dynamic loads:
⦁ Rolling loads
⦁ Vehicle configuration and weight
⦁ Pedestrian traffic:
⦁ Areas of high traffic need to be determined.
This information can then be used to determine the structural requirements of the raised access floor.
What are the site requirements?
The following site conditions are required for the installation of a raised access floor:
⦁ Dry and watertight areas at a temperature above 40° and a humidity below 75 % RH. This is required for both the installation works and also for material storage.
⦁ Sub floor to be in the following condition:
⦁ Free from wet or dry contamination.
⦁ Able to accept epoxy resin pedestal adhesive and if required mechanical fixings.
⦁ Any holes, joint lines etc in higher level sub floors should be sealed in order to prevent floor sealer leaking through to the level below.
⦁ The sub floor should be structurally strong enough to support the raised access floor and the environment it supports. The sub floor is required to be structurally strong enough to allow the storage of raised floor materials prior to installation (note: palletized materials typically weigh 1200 lbs and stand 48" high and are 26" square).
⦁ The surface of the concrete sub floor should ideally be of a medium tamp finish in order to give a reasonably flat surface without inducing the formation of weak surface laitance. A power float finish will normally give an excessively smooth surface which will prevent the dust sealer and the epoxy resin pedestal adhesive obtaining a good key and hence good bond onto the floor surface. In order to achieve a good bond onto a power float finish the subfloor will require to be suitably prepared by mechanical means which will remove weak surface laitance and provide a suitable surface for the application of floor sealer and pedestal adhesive.
General working conditions include:
⦁ Work areas to be free of other trades and their materials.
⦁ Unloading and distribution. Access for elevators and tractor trailors to areas of hard standing directly adjacent to the building entrance or hoist facilities. Access suitable for pallet trucks from elevators and trucks to distribute all materials including a hoist if appropriate to all points of the installation. Any changes in level in the sub floor should be overcome by temporary ramps at a gradient not exceeding 1: 8.
⦁ Adequate power supply to all work areas.
⦁ Adequate safety lighting to all work areas.
⦁ Work areas for the cutting of floor panels by the use of bandsaw.
⦁ Adequate means for the disposal of rubbish and debris.
⦁ Dry and watertight areas at a temperature above 40° and a humidity below 75 % RH. This is required for both the installation works and also for material storage.
⦁ Sub floor to be in the following condition:
⦁ Free from wet or dry contamination.
⦁ Able to accept epoxy resin pedestal adhesive and if required mechanical fixings.
⦁ Any holes, joint lines etc in higher level sub floors should be sealed in order to prevent floor sealer leaking through to the level below.
⦁ The sub floor should be structurally strong enough to support the raised access floor and the environment it supports. The sub floor is required to be structurally strong enough to allow the storage of raised floor materials prior to installation (note: palletized materials typically weigh 1200 lbs and stand 48" high and are 26" square).
⦁ The surface of the concrete sub floor should ideally be of a medium tamp finish in order to give a reasonably flat surface without inducing the formation of weak surface laitance. A power float finish will normally give an excessively smooth surface which will prevent the dust sealer and the epoxy resin pedestal adhesive obtaining a good key and hence good bond onto the floor surface. In order to achieve a good bond onto a power float finish the subfloor will require to be suitably prepared by mechanical means which will remove weak surface laitance and provide a suitable surface for the application of floor sealer and pedestal adhesive.
General working conditions include:
⦁ Work areas to be free of other trades and their materials.
⦁ Unloading and distribution. Access for elevators and tractor trailors to areas of hard standing directly adjacent to the building entrance or hoist facilities. Access suitable for pallet trucks from elevators and trucks to distribute all materials including a hoist if appropriate to all points of the installation. Any changes in level in the sub floor should be overcome by temporary ramps at a gradient not exceeding 1: 8.
⦁ Adequate power supply to all work areas.
⦁ Adequate safety lighting to all work areas.
⦁ Work areas for the cutting of floor panels by the use of bandsaw.
⦁ Adequate means for the disposal of rubbish and debris.
What are the potential timeframes?
The timeframes associated with the installation of a raised access floor are affected by many factors as outlined below:
⦁ The size and shape of the areas into which a raised floor is to be installed.
⦁ The exact specification of the raised access floor that is to be installed.
⦁ General condition of the building.
⦁ Poor quality of sub floor.
⦁ Building program and sequence of installation amongst other works.
⦁ Manufacturing times for raised floor components.
⦁ Obstacles on the sub floor that have to be worked around.
⦁ Availability of work areas.
⦁ Unloading and distribution conditions.
⦁ Availability and approval of necessary information.
Until these factors are suitably assessed for a specific project only then can installation timescales be evaluated. However an indicative installation rate of 300 sq ft per man 8 hr shift would be considered acceptable for an 'average' installation.
⦁ The size and shape of the areas into which a raised floor is to be installed.
⦁ The exact specification of the raised access floor that is to be installed.
⦁ General condition of the building.
⦁ Poor quality of sub floor.
⦁ Building program and sequence of installation amongst other works.
⦁ Manufacturing times for raised floor components.
⦁ Obstacles on the sub floor that have to be worked around.
⦁ Availability of work areas.
⦁ Unloading and distribution conditions.
⦁ Availability and approval of necessary information.
Until these factors are suitably assessed for a specific project only then can installation timescales be evaluated. However an indicative installation rate of 300 sq ft per man 8 hr shift would be considered acceptable for an 'average' installation.
Is it necessary to apply protection to the raised access floor?
Various factors surround the use of protection in relation to raised access floor installations. Generally protection should be used:
⦁ To all installations where the floor panels have a factory bonded finish.
⦁ To all areas where the floor panels will be heavily trafficked prior to the installation of the soft finishes i.e. carpet tiles.
⦁ To areas where the floor panels will not be heavily trafficked prior to the installation of the soft finishes.
⦁ To areas where significant repeated access is required to the floor void for the installation of services.
Generally protection may not be required.
⦁ To all installations where the floor panels have a factory bonded finish.
⦁ To all areas where the floor panels will be heavily trafficked prior to the installation of the soft finishes i.e. carpet tiles.
⦁ To areas where the floor panels will not be heavily trafficked prior to the installation of the soft finishes.
⦁ To areas where significant repeated access is required to the floor void for the installation of services.
Generally protection may not be required.
Materials commonly used for floor protection:
⦁ ¾" Plywood in sheet form
⦁ Hardboard in sheet form
⦁ Fire rated plastic sheet
⦁ Fire rated corrugated plastic sheet
These will be laid on the floor and if required the joints will be taped. ¾" Plywood will provide better protection against heavier levels of traffic.
⦁ Hardboard in sheet form
⦁ Fire rated plastic sheet
⦁ Fire rated corrugated plastic sheet
These will be laid on the floor and if required the joints will be taped. ¾" Plywood will provide better protection against heavier levels of traffic.
What building interface considerations are there?
The raised access floor will possibly interface with the following elements which will require consideration at the design phase:
⦁ Underfloor services
⦁ Thresholds at doorways/elevator lobbies, etc
⦁ Cladding/curtain walling
⦁ Perimeter heating
⦁ Skirting
⦁ Partitioning built off or through the raised floor
⦁ Changes in level e.g. ramps or steps
⦁ Underfloor services
⦁ Thresholds at doorways/elevator lobbies, etc
⦁ Cladding/curtain walling
⦁ Perimeter heating
⦁ Skirting
⦁ Partitioning built off or through the raised floor
⦁ Changes in level e.g. ramps or steps
How level will the installed raised access floor be?
⦁ The raised access floor will be installed level within 1/16" in 10' x 10' area.
Will the raised access floor require to be electrically earthed and how is this achieved?
In most cases due to steel used in its construction the raised access floor will require to be earthed in line with local conditions.
Will the raised access floor require to be electrically earthed and how is this achieved?
In most cases due to steel used in its construction the raised access floor will require to be earthed in line with local conditions.
What happens to the floor panels at perimeters?
At perimeters the floor panels are cut to fit on site by the use of a bandsaw.
Gravity lay perimeter cut panels will be mechanically fixed to the pedestals to provide additional stability. The cut edge of perimeter panels will normally be supported by the use of perimeter stringers or additional pedestals. As a matter of course all cut edges at door thresholds etc will have additional support by the use of perimeter stringers or pedestals.
Gravity lay perimeter cut panels will be mechanically fixed to the pedestals to provide additional stability. The cut edge of perimeter panels will normally be supported by the use of perimeter stringers or additional pedestals. As a matter of course all cut edges at door thresholds etc will have additional support by the use of perimeter stringers or pedestals.
Is the concrete sub floor sealed prior to the raised floor installation?
There are occasions when the concrete sub floor will be sealed with 2 coats of a epoxy resin coating in order to provide a surface that will withstand a lot of traffic during the installation period and provide a totally dust free void. These are normally large and specialised computer/data processing type environments.
How to avoid problems associated with raised access floors?
As the raised access floor performs a critical function within the working office environment, faults with the system can cause problems from simple annoyance through to major disruption. Many faults are rectifiable to a varying degree, however it is essential to consider the following key factors to prevent such occurrences.
Causes:
⦁ Use of inappropriate products and/or solutions
⦁ Use of inappropriate class or grade of raised access floor
⦁ Poor quality products and/or installation
⦁ Raised access floor not lifted and replaced in accordance with manufacturer's instructions.
⦁ Lack of appropriate maintenance.
⦁ Use of inappropriate class or grade of raised access floor
⦁ Poor quality products and/or installation
⦁ Raised access floor not lifted and replaced in accordance with manufacturer's instructions.
⦁ Lack of appropriate maintenance.
Effects:
⦁ Movement, rocking and squeaking of floor panels
⦁ Difficulty in removing and replacing panels
⦁ The floor may require modification in order to perform satisfactorily
⦁ Areas of floor or the complete floor may require replacement
⦁ Possible floor collapse with likely damage and injury.
In order to avoid the problems outlined it is important that the raised access floor be correctly specified at the outset. This specification should include not only the product requirements but also the installation requirements. Once installed the raised floor must be maintained correctly in line with the manufacturer's instructions.
⦁ Difficulty in removing and replacing panels
⦁ The floor may require modification in order to perform satisfactorily
⦁ Areas of floor or the complete floor may require replacement
⦁ Possible floor collapse with likely damage and injury.
In order to avoid the problems outlined it is important that the raised access floor be correctly specified at the outset. This specification should include not only the product requirements but also the installation requirements. Once installed the raised floor must be maintained correctly in line with the manufacturer's instructions.
How should a raised access floor be used?
Raised access flooring panels should only be lifted using the correct lifting device i.e. vacuum lifter or spiked carpet lifter. Panels should be lifted vertically with no hinging movement. Panels should be replaced in a vertical movement ensuring that the panel is seated on the pedestals correctly. Only single rows of panels should be lifted at any one time so as not to leave pedestals independent of panels, as they are prone to damage.
What are the maintenance requirements?
The exact maintenance requirements for any specific installation will be clearly spelled out in the Project Operating & Maintenance Manual. This will take due regard for the products and floor finishes used and also the anticipated loadings on the floor in terms of static loads, rolling loads and pedestrian traffic.
What are the maintenance requirements?
The exact maintenance requirements for any specific installation will be clearly spelled out in the Project Operating & Maintenance Manual. This will take due regard for the products and floor finishes used and also the anticipated loadings on the floor in terms of static loads, rolling loads and pedestrian traffic.
Source: ASM