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TILE INSTALLATION CONSIDERATIONS

Fourteen organisations, associations and corporations have worked to develop an Australian Standard for ceramic tiling. Standards from Europe and America were reviewed and adapted to suit Australian
conditions and techniques. In 1991 Australian Standard AS3958.1 “Guide to the Installation of Ceramic Tiles” was published. The following year Part 2 “Guide to the Selection of a Ceramic Tiling System” was released. These documents are excellent reference tools and should be included in any architectural or builders library.

Modern construction incorporates a wide variety of substrates. Concrete, timber and particleboard are used for floors, with brick, block, fibre cement sheeting and plaster board being used for walls. Each product has its own characteristics due to loads, chemical action, thermal and moisture movement, and each has different performance expectations. Any change in the surface that tiles are attached to can potentially be transmitted to the tile face – consequentially the substrate is a critical consideration when planning to tile floors and walls.

There are an extensive range of tilling products available – fixatives, cement mortar, cement based adhesives, organic adhesives and epoxy products. Each product is suited to different tiling environments. The surface, tile type and performance requirements of products must
be carefully considered when selecting a fixative.

The substrate must be carefully prepared in accordance with recommended standards. Concrete should be allowed to cure for a minimum of 28 days. Concrete should not have a steel trowel finish. Flexible panel products such as plasterboard must be fixed to properly constructed framing in strict accordance with the manufacturer’s instructions. Dust, wax, grease, release agents or curing compounds must be removed from the substrate and the adhesive manufacturer’s advice should be strictly followed.

The adhesive needs to be applied as directed by the manufacturer. Usually wall tiling must have a final bed thickness of no less than 1.5mm, a 6 x 6 mm notched trowel is usually recommended. Floor tiles are installed with a bed of approximately 4mm using a 10 x 10mm trowel. When correctly used the above trowels lay a thicker bed of adhesive which spreads when the tiles are placed, resulting in the required thickness and coverage – minimum of 85% coverage. No gaps should be left beneath the tiles. Occassionally lift a tile to check correct coverage is being maintained. Only one square metre of adhesive should be spread at a time, and regular checks should be made to ensure the adhesive has not skinned as this will result in an inadequate bond.

Grout lines should be left between the tiles that are a minimum of 1.5mm for wall tiling and 3mm for floors. Plastic crosses or similar devices can be used as an aid, but must be removed prior to grouting.

Ceramic tiles like other building materials go through dimensional changes with climatic conditions. The rate of change varies in each product. Ceramic tiles expand as they age due to moisture expansion as does surfaces like concrete that contracts with time, therefore, the tile layer is placed in compression due to differential movement. Movement joints, appropriate adhesive selection and correct installation reduce the resulting stress, minimising the risk of failure.

There are three types of movement joints required under AS3958.1. Adhesive manufacturers also include these joints in their instructions:

• Perimeter Joints should be provided at internal wall corners, wall and floor junctions, plumbing intrusions, where the tiles about fixtures such as baths, benchtops, or door frames. Where floors
meet walls the tiles can be laid before the skirting is fitted, hiding the joint for a neat finish. In domestic homes perimeter joints are usually all that are required.

• Intermediate Joints should be incorporated into the tiling in a grid pattern, at approximately 4.5metre intervals.

• Construction Joints in the structure must be carried through the tiling. This includes changes in the substrate, i.e. from brick to plaster. All movement joints must go from the substrate to the face of the tiling, be kept free of debris, adhesive etc. and be compressible, flexible and waterproof.

The current Australian standards covering tile installation are:

• AS3958.1 ”Guide to the Installation of Ceramic Tiles”,

• AS3958.2 “Guide to the Selection of a Ceramic Tiling System”.

The key considerations covered by the standards are:

• substrate type

• adhesive – compatible with substrate and tile

• substrate preparation

• adhesive coverage & thickness

• no skinned adhesive

• grout line width

• movement joints