Case 4

Cause of Defects

1. Designing and installing fixtures on a façade without considering the effects that they will have on the façade may yield adverse results. These fixtures when installed to protrude on a façade allow dirt to settle on its horizontal surfaces. The degree of stain formation due to protruding fixtures will depend on the width of protrusion of the fixture and the presence of corners created between the fixture and the façade.
2. The more the fixture protrudes from the façade, the larger the horizontal surface area for dirt to settle so that when runoff flows over the protrusion, the dirt will be washed off from the fixture and redeposited on the façade as stains. The protruding fixture causes staining in a much similar way as that of a ledge.
3. The method of fastening by which the fixture is attached to the façade has a large effect on the intensity of staining. Fixtures such as lighting and signage can be attached to the façade with clearance left in between the two or be fixed directly to the façade without clearance. In the former, disruption of even and regular runoff flow on the façade will be minimized and dirt that gathers on the protrusion cannot be washed onto the façade. However, the clearance left between the fixture and the façade must be wide enough to prevent debris and large dirt particles from collecting within the clearance gap. The mechanism by which stain marks form around signage can also be illustrated in Figure 1.
4. The horizontal and sloping surfaces present on the letterings are areas where more dirt can be retained. Stain streaks can originate either from the extreme vertical sides of the lettering or from behind the lettering. This is because of the different methods of attachment. In the former, the lettering was fixed directly to the façade without clearance between the façade and the lettering and thus dirt gathered on the lettering was washed onto the façade. In the latter, the lettering was not in direct contact with the façade and stains begin at the attachment points with no dirt from the lettering being washed onto the façade. Staining in the latter case would thus be less intense as shown in Figure 2.

Staining on a facade has a lot to do with the pattern of rainwater runoff, which in turn is dependent on the facade configuration, colour, texture, as well as the “roughness” and “water absorption” properties of the materials used:

Consequences

Staining if left unchecked results in loss in aesthetic value of the building. Long-term deposition of dirt stains on the facade may result in high cleaning costs and sometimes, the stains will be unremovable.