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Frequently Asked Questions
about Raised Access Flooring
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►
What is a raised access floor system?
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.
► What are the key 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.
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► Where is a raised access floor used?
Raised access flooring is used today in a wide range of
situations where there is a significant level of
building services. Examples include:
. Financial and
Insurance offices where there is a need for a
significant
level of computer/telecom equipment.
. National and Local Government
offices, again there is a need for a
significant
level of computer/telecom equipment.
. General administration buildings across the complete
range of industries
where the use of computer/telecom
equipment is
widespread.
. Call
Centers. Office environments set up to
handle large-scale customer
enquires thereby requiring significant levels of
computer/telecom equipment.
. Data
processing centers. Large scale computer
rooms set up for the processing
of electronic data e.g. customer information,
financial information.
. 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.
. Industries requiring clean room facilities such as
electronic and pharmaceutical.
. Light industrial and specialist industries where
flexibility and the use
of under floor services would be advantageous.
► Why use a raised access floor?
A raised access floor is used to provide a means of
creating a void below floor level which is capable of
ensuring building services are available at their
required destination. These services will typically
include the following:
. electrical
power
. data
. telecom
. environmental
control/air conditioning
. fire detection and suppression
. security
. water and drainage.
The use of a raised access floor will allow quick and
easy access to these services for maintenance reasons.
Also in today's modern office environment Churn is a
major issue. That is the number of times that the office
layout has to be modified to cater for changing
requirements brought about by new technology, new
personnel or new tenants to a building.
► What are the benefits of using a raised access floor?
Raised access floors are used extensively to provide the
following benefits:
. Quick and easy access to the ever increasing volume
of power, data and
telecom services found within a modern building.
. The underfloor void or cavity depth is often used as
a large duct for HVAC systems.
. In speculative buildings premises need to be
adaptable for the needs of incoming occupiers.
. 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.
. 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 are the alternatives to using a raised access
floor?
The alternatives are:
. Suspended ceilings. High level trunking runs are
above the ceiling and services drop down at the
required locations through service poles.
However any relocation, maintenance etc is at high level
thus causing major disruption to the office
area.
. Pre-cast trunking. This method was common in the
1970s. Steel trunking is cast into the structural
slab or topping screed along pre-defined
runs. No flexibility to cater for future changes.
. Skirting and Dado trunking. Steel or plastic trunking
which runs around the perimeters of individual
rooms. Adequate for small rooms but very
limited for larger areas, also limited cable capacity.
. Furniture. Specialist furniture which encompasses
in-built service runs. Expensive and limited to
vicinity of furniture runs.
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► What types of raised access floor are available?
There are two basic groups of raised access floor system
available each with their own advantages:
. 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.
. 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 woodcore.
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 enquires 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 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.
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► 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.
► Are there any standards governing the use of raised
access floors?
In August 2001 a European Standard was issued after
several years of consultation between all the European
manufacturers and was adopted as a British Standard in
November 2001, BS EN 12825 . The use of this standard is
increasing as it provides specifiers with increased
flexibility. This specification classifies raised
flooring products by their structural performance.
Installation issues are clarified by the Access Flooring
Association Code of Practice and further clarification
will occur when the National Building Specification K41
adopts this standard.
Other standards regularly in use are:-
CISCA. The
North American specification which often travels with
either the American client or American architects and is
regularly used internationally. This is an industry
driven specification and test method which is based upon
individual component testing.
► What type of surface finishes are available?
The following range of floor
finishes is
available:
Bare finish
Here the floor panel will not be finished with a surface
covering. The surface of the panel will normally be the
epoxy powder coated steel top sheet. This bare finished
raised floor will normally be covered on site by the
application of loose lay carpet tiles.
Factory applied
finishes
The following finishes can be supplied factory bonded to
the appropriate floor panel:
. Vinyl
. Anti static vinyl
. Static conductive vinyl
. Linoleum
. High
pressure laminate
. Rubber
. Carpet
. Wood in various forms
. Marble
. Stone, ceramic tiles.
. Other finishes may be available after evaluation.
► What range of finished floor heights (FFH) is
available?
Using standard pedestals finished floor heights from 3"
to 48" are achievable. Bespoke solutions for lower and
higher options are available.
As a general rule above a finished floor height of 24"
stringers will be introduced to provide additional
lateral stability.
► What is the exact definition of finished floor
height?
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The finished floor height (FFH) is defined as "The
nominal vertical dimension from the specified sub floor
level to the specified finished floor level".
► Why are raised floor voids used as air plenums and
what are the important criteria?
In certain circumstances the available space between the
underside of the raised floor panels and the sub floor
surface (known as the air
plenum) will be used as part of the
building's heating and ventilation system. In these
instances a pressure differential will be created
between the air within the plenum chamber i.e. under the
floor, and the air above the floor in the office
environment.
Product
considerations
In these situations there are certain attributes of the
raised access floor that become important. The leakage
of air through panel joints and at perimeters will need
to be kept within specific parameters for the required
air pressure differential. The air leakage rate through
the panel joint line is dependant on the size of gap
between the panels, which is dependant upon the
manufactured quality of the panel edge detail and also
the quality of the raised floor installation. The air
leakage at perimeters is also dependant upon the
specific detail design and the quality of the
installation.
Air leakage
rates
A typical air leakage rate for a raised floor system
without a finish i.e. carpet tiles, would be in the
region of 0.20 - 0.24 cfm/sq.ft. at a pressure
differential of 0.12 inches of water.
Air seals
Where the permitted air leakage rate through the raised
access floor complete with the required floor covering
is very low, or the specified air pressure differential
is high, the raised floor in its standard form may not
suffice. In these instances the raised floor panels may
be fitted with neoprene or similar gaskets to their
edges in order to form a seal when installed against
other similar panels. Alternatively stringers fitted
with gasket seals may be installed to seal the panel
joint lines.
Type testing
The air leakage rate through a raised access floor can
be determined by laboratory testing in order to give
indicative air leakage rates through both the panel
joint lines and perimeter detail. This can be undertaken
at a project specific pressure differential or across a
range of pressures.
Site testing
Alternatively the raised floor can be tested in its
entirety on site, as part of the installation process.
This on site testing can determine not only the air
leakage through the raised floor but also the leakage
through the floor void via other means e.g. incorrectly
sealed service penetrations through the sub floor slab.
Air outlets and
distribution
The conditioned air within the floor plenum is delivered
into the area above the floor via a range of outlets.
These are usually aluminium grilles of the same module
size as the floor panels. Dampers may be fitted to allow
control of the airflow through individual grilles in
order to achieve localised control to suit specific
local requirements. Perforated floor panels can be used
again fitted with dampers if required as an alternative
to grilles. A further alternative is use of smaller
circular air diffusers fitted into the floor panels,
again fitted with dampers to allow adjustment locally to
suit specific requirements. All of these air outlets are
readily relocated within the raised floor area as
requirements change.
► What is a carpet location system?
Carpet location systems are where the carpet tile is
fitted with small plastic location pips (normally four)
which locate into location holes in the panel top
surface. The carpet tile will be of the same module size
as the floor panel and will be laid on the same grid as
the raised floor panels (major air leakage). This has
the benefit that in order to gain access to the under
floor services the lifting of carpet and floor panels is
kept to a minimum. However many experts would say that
the quality of the finished carpet tile installation is
inferior to a conventional off grid (minimal air
leakage) carpet tile installation. Also the choice of
carpet tile may be significantly limited and incur
additional costs.
► How is a raised access floor installed?
With regard to the physical installation of the raised
access floor within a basic space there are two main
issues:
Finished floor height and level. Within a single floor
area a bench mark will be agreed between the floor
installer and the main contractor. This bench mark will
be directly related to the building bench mark. This
will determine the height to which the raised access
floor will be installed. The raised floor will be
installed level to this BM by the use of rotating laser.
Set out of the raised access floor system. The set out
of the raised access floor is an important aspect in
ensuring that the raised floor operates satisfactorily
throughout its anticipated life span. Depending on the
size and shape of specific floor areas and size and
location of any obstacles on the sub-floor a range of
solutions can be sought. Raised access flooring panels
are cut on site to fit at perimeter walls therefore a
best fit situation can be sought using the appropriate
floor panel module size. Ideally the setting out of the
panels and pedestals can be coordinated by:
. Working in line with other building modules to avoid
regular obstructions.
. Working out from the centre of an area.
. Working to column centers.
Cut panels should ideally be cut just under a full panel
width or a half panel width in order to minimize waste.
Cut panels of less than 6" width should be avoided in
order to maintain structural integrity. When it is not
possible to avoid small cut panels the following
solutions are available:
In-board cutting, the principle of maximizing the size
of a cut panel by additionally cutting the last field
panel adjacent to the perimeter. On certain product
ranges and structural grades oversize panels are
available as an alternative to the above.
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► 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 a 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.
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► 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:
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.
► 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
► 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.
► 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.
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► 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.
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.
► 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.
This
information is copyright © Kingspan at http://www.kingspanaccessfloors.co.uk
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