12.09 Cleaning
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Introduction
Cleaning may be carried out as a routine self-contained exercise or as part of a major refurbishment. This section is primarily concerned with the former aspect.
Cleaning of facades may be required for the following reasons:
- To remove deposits that may cause deterioration. Dirt may contain aggressive substances including chlorides and acids which cause corrosion of metals and deterioration of finishes. They may also be hygroscopic thus retaining moisture and maintaining an aggressive environment for long periods.
- To maintain appearance.
- To preserve function, the commonest example being light transmission of glass.
- To maintain the validity of guarantees. Guarantees for some finishes require regular cleaning to be carried out.
Frequency of cleaning
The frequency of cleaning depend on:
- Environment
- Building design
- Importance of maintaining appearance
- Required life of components
- Economic considerations
- Area involved
- Access
- Material characteristics
The environment will include both large scale factors such as the geographical location and proximity to the coast and local factors such as the presence of industrial pollution and orientation.
The accumulation of dirt on the building surface will be influenced by the design of the building. The flow of rainwater over the building surface can have a natural cleansing action. Overhanging eaves may be desirable for shading and weathertightness but can allow the accumulation of dirt in the sheltered area under the overhang.
Regular cleaning is more likely to be carried out on high profile prestige buildings where appearance is important or on highly visible areas around entrances.
Expenditure on cleaning to preserve the life of the cladding may not be justified if the building will become obsolete for other reasons before the predicted life of the cladding.
Cleaning of large areas of façade at regular intervals is expensive. It may be more economical to adopt a minimum maintenance policy and accept a slightly shorter service life.
Cleaning anodised aluminium window frames in conjunction with window cleaning may be practical whereas cleaning large areas of aluminium cladding panels may not.
Cleaning usually requires access to the outside of the façade, often at considerable height although in some cases windows can be cleaned from inside the building. For many buildings this provides both technical and financial difficulties. For new buildings requirements for access should be considered at the design stage.
Requirements for cleaning vary according to the material concerned. Some materials, notably lead and copper, form a natural patina, which gives a characteristic appearance, is resistant to deterioration and would be lost by cleaning. With these materials regular cleaning is undesirable although in some cases staining may occur shortly after construction due to contamination with other construction materials and in such circumstances cleaning may be necessary. The table below gives an indication of cleaning requirements for materials commonly used in cladding.
| Material | Recommended cleaning regime | Reference | |
| Glass and plastic glazing materials | Regular cleaning required to maintain light transmission and appearance. Failure to clean regularly results in deposits becoming baked on and difficult to remove. Integrity of glazing unlikely to be affected. | BS6262 | |
| Lead Copper Zinc | Regular cleaning not required and can be detrimental due to disruption of patina. | BS6270 Part3 | |
| u-pvc | Regular cleaning helps to maintain surface finish although dirt is unlikely to cause serious deterioration and may provide some protection from ultraviolet. | ||
| Aluminium | Regular cleaning recommended to maintain appearance. The recommended frequency of cleaning ranges from 1 to 6 months depending on severity of exposure. | BS6270 Part3 BS3987 AppE | |
| Organic coatings | Regular cleaning is recommended to maintain the durability of the coating. Manufacturers may require cleaning at intervals of 3 to 18 months depending on environment to maintain the validity of their guarantee. | BS6496 AppA&B BS6497 AppA&B | |
| Stainless steel | Regular cleaning is recommended at intervals ranging from 3 months in polluted industrial areas to 6 months in rural areas. | BS6270 Part3 | |
| Concrete Brickwork | Routine cleaning of these materials is unlikely to be necessary although local cleaning to remove stains and graffiti may be required. General cleaning of these materials may be carried out to remove excessive build up of dirt as part of refurbishment. | BS8221 Part1 | |
| Stone | Although dirt may attack some stones cleaning may also be detrimental. Requirements depend on the type of stone. Polished marble requires cleaning at intervals of about 6 months to maintain the surface finish. | BS8221 Part1 | |
Table: Cleaning requirements for different cladding materials | |||
Cleaning methods
For most materials requiring regular cleaning, the preferred method of cleaning is to wash down with warm water containing mild detergent. The use of a soft bristle brush may be permitted for removal of deposits but more abrasive methods should generally be avoided. This should be followed by rinsing with clean water and wiping dry.
Where simple washing down is not effective, chemical cleaning agents and abrasives may be used. Different chemical cleaners are suitable for different materials and the references in the Table above give guidance on the selection of appropriate methods. Trials of proposed cleaning methods on inconspicuous areas may be required to check their suitability. Protection of adjacent materials may also be required.
Cleaning may involve the use of aggressive chemicals and work at height. The safety of cleaning staff and building users needs to be considered before the work is carried out.