Case 6

Cause of Defects

The air exhausted through a louver unit usually contains a high concentration of dirt that accumulates at the top face of each louver panel. For this reason, areas below louver units are often stained.

When there is driving rain, the rainwater that impacts on the louver pane will carry the dirt along with it when it drips from louver pane to louver pane. The irregular runoff flow pattern results in irregular stain marks being formed along the stretch of panel under the louver unit (Figure1 and 2). As compared to other panels on the facade, staining on this panel below the louver unit was more distinct.

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.

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 might become removable.