TN 21.23 The Installation of Resin Agglomerate Stone Tiles

INTRODUCTION
Resin agglomerated tiles have become increasingly a popular choice of floor finish, as they offer a cost-effective alternative to natural stone. These tiles are manufactured in an array of colours and are ‘engineered’ to have some improved mechanical and physical properties such as scratch resistance and flexural strength.
A resin agglomerate stone tile is a composite material, based upon the use of recycled natural stone aggregates or stone pieces which are then bound together at the manufacturing stage using a synthetic resin. The resin bound stone is then formed by vibration and compression under vacuum into large blocks. These blocks are then allowed to cure before being sawn into slabs, calibrated to the correct size and thickness, polished, then accurately cut into the required tile sizes.
The agglomerated stone to resin binder ratio has a direct affect upon the physical, mechanical and performance properties of the tiles. For example, use of quartz or granite agglomerates produce in general a harder wearing tile with increased resistance to acidic chemicals when compared with those based on marble agglomerates. Two main types of polymer resin binder are used in the tile manufacture and these are either epoxide or polyester. The ratio of resin binder to agglomerates varies from 5% to 7% (with 95% to 93% Agglomerate). The higher the percentage of resin present; then the greater the abrasion resistance is reduced. This is especially evident with increases in the Coefficient of Thermal Expansion of the tile.
THERMAL MOVEMENT
Materials may undergo dimensional changes when subjected to heat fluctuation. This is known as the Coefficient of Thermal Expansion. When considering the tile, the tile adhesive and the substrate, the Coefficient of Thermal Expansion for a typical constructional sub-floor such as concrete or cement; sand screed is like a cementitious based tile adhesive.
However, a resin agglomerated stone has a higher Coefficient of Thermal Expansion C.T.E) in comparison. In simple terms the resin agglomerated stone has a high modulus of rupture (bending strength) and is being ‘restrained’ by the tile adhesive. However due to heating and cooling cycles, a relatively small amount of heat expansion and contraction can exert a high level of stress on the restraining layer i.e. the tile adhesive. The larger the tile dimensions, the greater the amount of dimensional changes caused by thermal expansion as temperature increases.
N.B Consult the resin agglomerate stone supplier regarding the suitability for application onto underfloor or undertile floor heating.

MOISTURE MOVEMENT
It is important to note that resin agglomerated stone tiles do have varying degrees of moisture sensitivity which means that these tiles can be susceptible to differential moisture expansion. This can often lead to a potential ‘curling’ of the tiles. The Tile Association (TTA) technical document on Tiling with Resin Agglomerated Tiles recommends that:
“Cementitious floor screeds to receive resin agglomerated tiles should be completely cured and tested to ensure that they have a moisture content of not more than 2% by weight or 75% relative humidity using the appropriate test equipment and also that an appropriate adhesive is chosen” (Clause 3.5 Moisture Sensitivity).
Simply put, the use of a cementitious based tile adhesive or screed will introduce moisture directly beneath the resin agglomerated stone tile which may be taken up slowly by the tile. Some loss of moisture will occur whilst the tile joints remain unfilled, however this process will be slower. The tiles are available in various size formats including large formats (i.e. with one edge length 600mm or greater) up to typically 1200mm x 1200mm. The larger the tile in size, the more likely that moisture will become trapped at the tile/adhesive interface. In the case of some resin agglomerated tiles, this will increase the risk of curling of the tiles away from the tile adhesive bed. The correct selection of tile adhesive is, therefore, essential.
TILE ADHESIVE SELECTION
British standards code of practice BS 5385: Part 5 and floor tiling Design and installation of terrazzo, natural stone and agglomerated stone tile and slab flooring – Code of Practice offers the following recommendations in BS 5385: Part 3;
“To avoid moisture from the adhesive bed distorting resin-based agglomerated stone, reaction resin adhesives, or quick drying low alkalinity cement-based adhesives should be used”.
Dependent upon the background substrate to which the tiles will be fixed, use BAL RAPID FLEX ONE with BAL ADMIX AD1 (Diluted 3 parts water: 1 part BAL ADMIX AD1 by volume) may be used for floors and walls.
Where the resin agglomerate stone is especially moisture sensitive use of a suitable reaction resin tile adhesive such as BAL ABSOLUTE GROUT.
GROUT SELECTION
Joints between the resin agglomerated stone may be filled with either:
BAL MICROMAX3 ECO with BAL ADMIX GT1 (Diluted 2 parts water: 1 part BAL ADMIX GT1 by volume).
or
BAL ABSOLUTE GROUT.
Note; Check the potential risk of staining by applying grout to a few tiles in a small trail area. If discolouration occurs or difficulties are encountered with cleaning off (the surplus grout), apply BAL PROTECTIVE SEALER and repeat the trial. Alternatively, contact the manufacturer or supplier of the tile for sealing advice.

MOVEMENT JOINTS
BS 5385: Part 5: Design and Installation of terrazzo, natural stone and agglomerated stone tile and slab flooring – Code of practice gives advice on the location of movement joints.
Section 11 Agglomerated stone, clause 11.4 Movement joints gives additional advice as follows;
“11.4.1 General the type and positions of movement joints in agglomerated stone flooring should be as described in Clause 8, but resin based units require movement joints at a higher frequency that take into account their greatly increased coefficient of thermal expansion. NOTE Resin based flooring units can have a coefficient of thermal expansion more than three times that of cement terrazzo and natural stone”.
“11.4.3 Perimeter joints Where flooring abuts restraining surfaces such as perimeter walls, columns, kerbs, steps and plant fixed to the base, perimeter joints should be installed unless the distance between restraining surfaces is less than 2 m”.
“11.4.4 Intermediate joints Very large floors should be divided into bays by incorporating type C joints (see Figure 4) at not more than 10 m intervals subdivided into smaller bays by stress-relieving joints 3 m to 5 m apart”.
The Tile Association (TTA) technical document on Tiling with Resin Agglomerated Tiles
Advises that: “In normal conditions movement joints should be installed at bay sizes not exceeding 36m² and for underfloor heating not more than 25m²”.
TECHNICAL ADVISORY SERVICE
For free expert guidance on the use of BAL products, or any aspect of ceramic tiling with BAL products, contact the BAL TECHNICAL ADVISORY SERVICE on 01782 591120.
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NOTE
The customer must verify the suitability of any information, opinion, recommendation or advice (“information”) provided by the Company for the particular application for which any goods are intended to be used and the Company accepts no liability (whether in contract, tort or otherwise) whatsoever for any loss, damage or expense arising from the misuse of any information it supplies, nor for the use of any information in or for applications which are unsuitable or inappropriate. Building Adhesives Ltd operates a continuous research and development programme and reserves the right to alter or to update information from time to time.

“Note: Any advice, opinion or information is given to assist the use of the Company’s products on the basis that the user will ensure its suitability for the application intended. In particular the Company cannot accept liability for loss or damage which may arise from incorrect use of its products or from poor workmanship. The Company operates a continuous research and development programme and reserves the right to update information without notice.”