External cladding is the outermost envelope of a building and normally carries no loading beyond its own weight plus the loads imposed by rain, snow, and wind, and during maintenance. External cladding thus functions purely as a protective and decorative envelope for the structure and contents of a building.

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The main technical advantage of lightweight external claddings such as timber is that the heavy and bulky masonry wall can be eliminated from the outside of the building. With suitable design a lightweight cladding, when combined with a lightweight roof covering and a lightweight wall structure, can produce very significant weight savings over masonry cladding.

 

This allows the foundation depth of a typical house to be reduced and could offer savings of between 20–40% of the below ground costs. The money saved can then be allocated to increasing the insulation of the building so that, for no additional cost relative to masonry cladding, a much more energy efficient building envelope can be created.

 

Timber cladding offers considerable design flexibility and can easily accommodate both traditional and contemporary styles of building.

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The most common form of timber cladding consists of boards laid vertically, diagonally or horizontally with either overlapping or flush faces. There are variations in board width, surface finish, profile shape, joint design, and colours.

 

The most common type of board cladding is where the boards are laid horizontally. The boards can be used in a simple overlap design, feather or square edged, rebated feather edge, shiplap or tongue and groove design.

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Cladding softwoods are Redwood, Larch, Douglas Fir, and Western Red Cedar. Hardwoods used are Oak, and Sweet Chestnut. Tropical hardwoods that are commonly used for cladding are Sapele, Iroko and Meranti.

 

Specialised woods are also used for cladding such as Thermowood which is a highly durable heat treated chemical free softwood, and Accoya which is a modified wood that has excellent durability and dimensional stability.​