Sheathing in construction

In very general terms, 'sheathing' is a covering or supporting structure that has a similar function to the sheath of a blade; that is, it acts as a cover or case.

In the construction industry, the term ‘sheathing’, or 'sheathing board' can be used to refer to a layer of board or panel material that forms a part of floor, wall and roof assemblies. The outer sheathing board strengthens the assembly, provides a surface for other materials to be applied to and may give some degree of weather resistance.

The materials most commonly used for sheathing include; engineered timber, plywood, gypsum and oriented strand board (OSB).

Floor sheathing is typically a tongue and groove material that carries live loads down to the floor joists beneath. It is generally installed after a floor frame and been built but before the walls have been built up.

Wall sheathing can be structural or non-structural and on external walls can help protect against wind and water penetration.

Roof sheathing is generally structural as it helps to brace the roof frame. A covering is generally applied over the top of the sheathing.

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