Case 1

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Cause of Defects

External wall tiling systems commonly found in Singapore are brick and glazed tile finishes, predominantly on plastered or roughened concrete substrates.

Tile debonding can be traced to one or several of the following reasons:

differential structural movements;
differential movement between the tiles and background; Typical ceramic tiles have a coefficient of thermal expansion ranging from 4 to 8 x 10⁻⁶. The effect of the difference in the coefficients is dependent on whether the cement heats up to the same temperature as the tile, on the duration and intensity of the sunshine, and on the extent of the thermal conductivity into the structure.
improper selection of adhesives
inadequate or defective expansion joints
substrate may not have been cured properly before the installation of tiles
bad workmanship; Too long delay between the application of adhesive and the laying of tiles may also lead to a loss of surface tack resulting in poor adhesion.
harsh tropical environmental conditions of sudden rainfalls, high humidity and high surface temperature of up to 70°C. Such wetting and drying cycles exerts stresses on the tile bed which induces movements of different magnitudes.
poor maintenance procedures to detect possible tile failures
building settlement
contamination of the back of the tile with dust and dirt deposits which form a barrier against proper adhesion between the interfaces.
failure to soak porous tiles before tiling. This results in high suction of the tiles which would remove part of the water from the cement mortar tile bed and affect the bond strength.
In tropical conditions where there is presence of continuous high humidity will result in moisture seeping through into the backing of the tiles. This moisture will reduce the adhesion strength of adhesives by dissolving some of the adhesive compounds and cause the tiles to debond.

Consequences

Tile debonding does not affect the structural integrity of the building but affects the aesthetic value of the façade. Tile debonding and falling off from high levels can endangered lives. The exposed substrate may allow water to enter. Replacement will be troublesome and usually noticeable. Obtaining the same tile to match will also be difficult.

The de-bonding may occur between or within any of the interfaces, between elements or within an element, or a combination of the above. Examination of the failure mode is hence important for devising the optimum remedial action.

Failure mechanism may also follow similar cases as follows:

(a) Tile delamination from the façade at gable end

(b) Tile delamination between adhesive and substrate