Introduction

The cladding of buildings is one of the most expressive, inspiring and complex aspects of building design. As the use of the structural frame developed the ensuing separation between structure and envelope led to a growth in the use of many new and different forms of cladding systems. Cladding has to service a number of critical functions in a series of complex relationships:

• protection and security - from the environment, from negative aspects of society
• comfort - light, humidity, sound, ventilation
• expression and celebration
• sustainability - contribution to life cycle costing; maintenance and durability

Many materials and process are used in cladding.

Many materials and processes are used in cladding: stone (in blocks and veneers), concrete, ceramics, steel, aluminium and other metals, glass, and plastics. These materials can be further subdivided by different forming and processing techniques.

A brief analysis of the one bay of the facade of the Hong Kong Shanghai Bank reveals a large number of different materials and processing and fabrication operations, with many of the components manufactured solely for this building. This analysis is by no means comprehensive and doesn't include installation.

Some important cladding terms which are often confused include:

• curtain wall - a non-loadbearing external wall
• rainscreen - comprises a number of layers each with a separate function
• overcladding - the addition of a new skin over the existing

Curtain wall is a general term used to define a non-load bearing external wall, supported from the frame. The precise definition tends to vary. It is most often used in connection with factory produced repetitive elements of framing and panels of glass or opaque materials (LINK section 5.3). In this context the development of curtain walling is almost synonymous with the development of multi-storey framed buildings

Rainscreen cladding defines a multi-layered system that has its origins in traditional and vernacular architecture, for example tile hanging. In contemporary construction each of the each of the layers performs a separate functions with regard to weathertighness, insulation and ventilation.

Overcladding is the addition of a new skin of cladding applied onto the existing cladding, often to increase the thermal insulation, to improve the appearance, to minimise or eliminate further deterioration of the existing building fabric.