Case 1

Good Practices

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.

Paint

Material

• Avoid vibrant colours that will show traces of discolouration easily. If it is necessary to use such colours, select colours that are more stable and are more resistant to weathering.
• Deterioration/ erosion of pigment may also be due to low quality paint or paint with water sensitive pigments.Use weather resistant paint or paints that are more stable. Application of paint system should follow closely to the manufacturer’s specifications to achieve best results [1-4]
  Use only appropriate coat as recommended by the manufacturer.
• Prepare receiving surface and apply appropriate sealer to protect the paint.Select a colour that is more stable and use an appropriate coating system [5-6].

Sunshading devices

Installation of sun breaking devices can reduce the amount of UV light attacking the painted facade.

Water repellent and surface coating system

Clear water repellents are most effective at reducing the amount of water absorbed by the brick masonry. Thus, they can help reduce staining and fungi growth caused by moisture absorption, particularly on highly absorptive masonry.

Surface preparation is important. The surface on which the coating is to be applied has to be:

• cleaned by grinding, chemical etching or blasting.
• dried by allowing the wall to cure for a few days before the coating is applied. During rainy periods, the walls should be protected with a plastic covering so that the drying is not interrupted.

Other surface protection systems include:

• Impregnation systems:
  • Prevent penetration of water and solutions into brick without hindering the escape of internal moisture from concrete
• Materials used [3]:
  • silicon organic solutions
  • resins
  • oils
• Sealers
  • Heavy barrier against penetrating solutions but may hinder the escape of internal moisture
• Materials used [3]:
  • epoxy resins (EP)
  • polyurethane resins (PU)
  • unsaturated polyester resins (UP)
• Coatings
  • compared to sealers, they provide additional protection against mechanical influence.
  • increased resistance to diffusion of internal moisture
• Materials used [3]:
  • plastic modified cement systems and resins