Case 1

Good Practices

Dampness

Prolonged dampness on a facade is determined, among other, the following:
(1) Rainwater runoff pattern
(2) Water absorption coefficient and texture of the material

Water absorption affecting staining
Source: Flow and Changes in Appearance, 1996

For more information on staining issue on facade, please visit “Staining of Facades“.

Design

The material selection for exposed surfaces, and their regularity and surface texture should be detailed to
prevent moisture retention. Areas prone to high moisture exposure shall be made impervious with adequate waterproofing systems. Also such surfaces should be without impediments (e.g. built-in cabinet, fixed equipment/services) to ensure access for inspection and to ensure ease of cleaning. Access for adequate cleaning should be provided in accordance with BS 8221- 1, SS 509-1 or equivalent. Ventilate to prevent moisture retention on floor/wall/ceiling. For natural ventilation, opening > 5% of floor area. For mechanical ventilation, air exchange rate > 20 air changes per hour, in accordance
with “CP on Environmental Health”.

Construction

Exterior surfaces of porous building material (e.g., cellulose, brick, stone, cement rendering) can develop biological growth. Avoid such growth as much as possible with treatments of anti-algae/anti-fungus solutions and allow to dry before painting/repainting (SS 652: B.5.2.1). Improve ventilation and remove sources of dampness to dry out the substrates as thoroughly as possible during painting works in
accordance with BS 6150, SS 542 or equivalent. Ensure access ducts are connected to the mechanical
ventilation system. The exhaust system shall dispel the air directly outdoors.

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 to accommodate moisture and thermal movements. 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.

Construction

General sequence of work 

External tiling works should commence at an appropriate level and proceed downwards. The sequence of commencing from top down will prevent contamination of completed tiling at lower levels from works above. It also allows for quicker dismantling of scaffolding because if the tiling work commences from the lower levels, the scaffolds cannot be removed until the tiling works at the upper levels are completed.

For multi-storey construction, some form of deflection of the building can occur at lower levels as the building increases in height as loading increases accordingly. Hence, by selecting an appropriate level to commence tiling, movement due to deflection at the lower levels can be accommodated before tiling works begins.

Actual tile installation process

The steps involved in the installation of a tiled façade are given below. Good practices during each of the step will be necessary for the entire tiling system to function properly. Inappropriate practices at any one step can lead to the failure of the entire tiling system even though the rest of the steps are performed correctly.

Treat the tiles with fungicide before installation. This can prevent growths of biological agents on tiles. Apply a coat of water repellent to the tiled surface so as to minimise water adhesion to the tiles.