Case 5

Good Practices

Where possible, panels should be of regular size and shape throughout the facade. This will ensure that joints are aligned and regular.

Expansion joints that are deliberately designed to be out of alignment may cause uncontrolled runoff flow. Streams of runoff flowing along the sides of a vertical joint would deposit the dirt carried along when it spills onto the panel below. Expansion joints both closed and open should be made to be in alignment through the height of the façade. Runoff flow can then be controlled to flow from the top of the façade to the bottom and subsequently be drained off the façade.

Attention must also be paid to workmanship during the construction of these joints so that they are in line. Poor workmanship can sometimes results in joints being misaligned and causes flow to be affected and bring about long streaks of stains beneath where the misalignment had occurred (Figure 1). This may happen on tiled facades where on-site installation is heavy and misalignment resulting from poor workmanship may occur. By encouraging prefabrication and using façade systems that require little on-site installation, such a problem resulting from poor workmanship can be rectified

Design

Specify material and application methods for water repellence of porous masonry in accordance with BS 8221-2, SS 509-2 or equivalent. Throw off water from the façade altogether through an outward projecting sill or overhanging eaves (which incorporate a throat or drip lines on its underside) or provide blocking features such as copings/flashings. Use efficient scupper drains/downpipes to channel water down and away from the façade. To provide drip grooves along the underside of projecting features. Specify a paint system, which is permeable to avoid any paint defects which may cause staining.

Render the detailing for open joints as opposed to butt joints to avoid sealant staining. To use nonbleed sealants so as to prevent staining from silicone oil. Recommend joint designs, which are able to retain rainwater runoff within joints and expansion joints designated to provide vertical runoff carrying dirt down along the façade surface. Specify façade self-cleaning applications (e.g., TiO2, superhydrophobic
paint products, etc.) with due consideration given to site orientation, sunshades and protruding features. To understand the impacts of environmental, material, design and maintenance aspects on rainwater runoff.

See also Staining of Facades

Construction

Paint façade surfaces evenly with no patchiness. The finished texture should be uniform in colour. Ensure proper rendering to control surface granularity and local faults as it influences colour uniformity of the external façade in accordance with ISO 7361 or equivalent. Correct sealant applications to ensure consistent and continuous quality. Avoid misaligned panels of cladding in accordance with BS 8000-0 or equivalent. Refer to the planning of the painting programme, including inspection regime (initial and routine inspections) for buildings in accordance with BS 6150, SS 542 or equivalent.

Use self-cleaning coatings on newly built substrates for increased success in its performance. All construction/repair works on a façade surface should be done prior to application of a water repellent in accordance with BS 8221-2, SS 509-2 or equivalent. For serviceability of exterior façade surfaces, adopt ASTM E1667-95a or equivalent. It is important as it dictates the building’s individual and corporate identity. The correct application of TiO2 coating is crucial to ensure proper adhesion to the substrate. It is also challenging to check the proper application of the coating, especially on high-rise buildings, due to
its transparent property.