Tile installation on raised access flooring

A raised floor (also known as raised flooring, access flooring) provides an elevated structural floor above a existing substrate to create a for the passage of mechanical and electrical services. Raised floors are widely used in modern office buildings, and in specialized areas such as command centers, Information technology data centers and computer rooms, where there is a requirement to route mechanical services and cables, wiring, and electrical supply. 

Raised flooring can be installed at varying heights from 2 inches (51 mm) to heights above 4 feet (1,200 mm) to suit services that may be accommodated beneath. Additional structural support and lighting are often provided when a floor is raised enough for a person to crawl or even walk beneath.

The raised flooring system shall consist of pedestals adhered to the subfloor using a polyurethane adhesive (or similar appropriate adhesive). The pedestals are adjustable allowing for both accurate levelling of the body of the raised flooring system and levels between the panels. The levelling from one panel to another or “lipping” from one panel to another shall not exceed 0.75mm. 

The pedestals are set out at 600mm centres to facilitate supporting the panel at each corner. A polypropylene gasket is then placed on top of the pedestal and the  raised flooring

system panel placed on top of the gasket thus the panel is supported at all four corners. The heavy grade floor panel is then screwed down to the pedestal head using a M6 self-tapping screw.

This should provide rigid support for an intermediate substrate secured to the top surface of the raised access flooring by fixings at centres not more than 300mm apart.  Once completed this surface should then be sufficiently rigid and ready for the application of floor tiles.

Tiles should not be fixed directly to the panel of raised flooring but shall be installed with an intermediate substrate like:....

 1. Plywood, Grade 3 (as defined in EN6363-3),  should be sealed with sealer coat at back and sides to prevent the ingress of moisture or use Marine grade moisture insensitive wood. 

2. Proprietary tile backer board of a minimum thickness of 6mm.

3. A proprietary uncoupling/reinforcement membrane.

4. Calcium sulfate lapped edge boards

5. When considering installing ceramic tiles installed over resilient acoustic flooring systems, the coefficient of restitution for the tiled finish must be at least 0.55.

In order to achieve this, the tile should, therefore, be a minimum thickness of 11mm and meet the requirements for BS EN 14411.  Further advice may be found in the TTA Technical Document “Ceramic and Natural Stone Floor Tiling to Acoustic System to meet the requirements of The Building Regulations 2000 Approved Document E Resistant to the Passage of Sound 2003”

Tile adhesive selected is able to fully restrain the selected rigid tile finish and thus accommodate the normal stresses associated with the environment to which the tiled installation will be subjected during its life in service. The tile adhesives must conform to BS EN 12004:2007.  The adhesive selected should be deformable (Category S1) and be capable of withstanding a degree of limited movement and deflection. 

If the area is for underfloor or electric undertile floor heating, the adhesive shall be capable of withstanding changes due to thermal influences, the conduction of heat through the background to the tiled finish and any associated movement, coefficients of thermal expansions.

Some of the raised flooring system / floor system will have chequered plates at the top installed for different requirement, lets discuss how to tile on them.

The following is a general guide to the minimum requirements for tile adhesive selected for fixing to steel encapsulated raised flooring systems of common floor tile finishes:

a)  Overlaid with minimum 15mm thickness plywood Grade 3 or C (as defined in BS EN 636): 

1) For ceramic tiles (including porcelain): use a polymer modified S1 adhesive (C1 or C2). 

2) For natural stone use a relatively low water demand, rapid setting, polymer modified  highly deformable S1 adhesive (C1 or C2).

3) For agglomerated stone use a two part, highly polymer modified adhesive (Categories R1, R2, C2F S1) as recommended...for moer details refer to : Tiling with Resin Agglomerated Tiles.

b) Proprietary tile backer board.

1. For ceramic tiles (including porcelain): Use a highly polymer modified (C2) adhesive or a highly polymer modified deformable adhesive (C1 S1 or C2 S1)

2. For natural stone: Use a relatively low water demand, rapid setting, polymer modified adhesive (C1 or C2).

3. For agglomerated stone use a two part, highly polymer modified adhesive (Categories R1, R2, C2F S1)

c)  Calcium Sulfate Overlay Lapped Systems: use of either a C1 or C2 adhesive with S1 performance.

d)  Uncoupling membranes - Contact tile adhesive manufacturer.

The selection of grout should be based on traffic load and service requirements. Either class CG2 or RG type grout conforming to BS EN 13888 should be used. 

Movement joints  

a. In all cases perimeter movement joints should be installed.

b. Intermediate movement joints should be installed so bay sizes are no greater than 100 sqm.

c. Where underfloor heating systems are installed intermediate movement joints should

be more frequent, 

c.1 Bay sizes no greater than 40 sq. metres in area for ceramic and natural stone tiles and 25 sq. metres. 

c.2 In area for resin agglomerated tiles. 

The panels formed should be square to rectangular with a length to width ratio of no more

than 8 x 5 metres.

d. Any movement joint in the raised flooring system should be brought through the tiling.

Many thanks to : google.com, Doc88.com, The Tile Association.. from where the details were collected.