Case 1

Good Practices

Design

Recommend surface treatment and protection in accordance with SS 509-2, BS 8221-2 or equivalent. Ensure proper detailing of window, door, and abutment points where water seepage can occur and cause delamination. Design movement joints are recommended on the structural concrete in accordance with BS 6093 or equivalent. As early as 1992, the then Public Work Department (PWD) — now Building and Construction Authority (BCA) — issued a memo discouraging the use of tiles (ceramic and stone tiles bedded with adhesive) on façades of buildings exceeding 4 storeys.

Construction

Sufficiently remove curing agent (used for early stripping of formwork) to ensure proper adhesion on the substrate. Ensure proper substrate preparation (cleaning) prior to application of plaster/tile finishing. Perform quality workmanship on façade through the correct handling and angle of application to prevent delamination and debonding in accordance with BS 8000-0 or equivalent. Lay adhesive and tiles in the sequence according to the manufacturer’s instructions. Adopt the performance requirements for curtain
wall, including safety in accordance with BS EN 12179, ASTM E2270-14 or equivalent.

Tile

Detailing

• Window, door or abutment are points of weakness where tile edges can be exposed and water ingress can occur. Metal cappings or flashings can be used.
• Horizontally tiled surfaces should be avoided and openings should be set back within the elevations.

Structural Frame

• An understanding of the type of structural frame and the amount of movement that could be experienced is needed.
• Structural concrete to which the tiles adhere to creeps under dead load and live loads. Proper movement joints of about 10mm wide, horizontally at every floor level, and at about 4m centers vertically is needed. They should be as deep as the tile and adhesive, and filled with a stable sealant such as polyurethane. Proper movement joints must be incorporated to prevent overall shrinkage of the frame and to allow expansion of the tiling.
• The frame must be regular so that a thin coat of adhesive will be able to adhere tiles to the surface.
• The reinforcement bars within the concrete substrate should be inspected regularly for signs of corrosion as an unstable background would bring about failure of tile covering.

Materials

• The suitability of a ceramic tile for external wall depends mainly on its water absorption rate and thermal expansion.
• The tile bed has to be sufficiently flexible so that it can take the moisture and thermal movement. Cement based polymer latex or resin are suitable for tiles. The grouting material is normally of the same type as tile bed, compatible to the tile bed and the tile.
• Single-fired vitrified wall tiles (glazed or unglazed) are especially suited for external walls subject to thermal shock conditions on tropical climates. The ceramic tile can withstand short-term changes in temperature over a range of 0°C to 150°C because of its microstructural characteristics.
• The tiles shall be fully tested to meet the performance requirements stipulated in the contract before mass installation [5-7].

Construction [7-10]

Movement joints are required in 4.5m intervals in areas in excess of 4.5m of external tiling [2].

Tile joints

• Joints should be filled with a grout of good adhesion and low shrinkage.
• The grout should be reasonably flush with the tile face to ensure adequate thickness.
• It must also be complete and flexible both at the time of installation and after.

Adhesion

• Clean the surface thoroughly to remove foreign particles accumulated on floor. This is to ensure that the bonding of the rendering will not be affected.
• If the bedding material is ordinary cement mortar (Figure 4a), the surface (render) should be damped to prevent any suction of water from screed/ or render. However, if the bedding material is an adhesive (Figure 4b), the manufacturer’s instructions should strictly be followed. These instructions such as surface preparation, mixing and application of adhesives are clearly labeled on the packing.
• The substrate has to be sound and even so that the adhesive will have a stable background.
• The substrate needs to adequately roughened so that the adhesive will bond.
• Concrete is a difficult surface to bond plaster to. It is hard, smooth and dense and will require careful and thorough preparation. Brick infill may be slightly easier. If mechanical roughening of the concrete cannot be adequately achieved then it may be advisable to plaster on to mechanically secured stainless steel mesh.
• The adhesive used should cover the tile completely and should be applied using the correct mix, thickness and consistency. It should also be ensured that retarders or parting oils are removed from concrete faces prior to tiling.
• Tiles should also be lightweight. Tiling should also not be done over existing tiling.
• Cleaning and roughening the surface of substrates is very important to ensure good adhesion of tile bed. It is good practice to limit the rendering layer to 20-25mm. If further thickness is needed use reinforcement in a form of a lath or a wire mesh.

Quality assurance

• On-site tests such as pull out test for anchors can be done to ensure the required strength stated by the specifications is met (Figure 1).