Buildings have two major classes of systems: Structural and Non structural systems.
A structural system by its intrinsic nature, composition, position, or arrangement, provides a whole that stays stable, in equilibrium, or constant (yet may be mobile like a ship, spacecraft etc.).
The structural subsystems of a building system must exist in the required location or be available at the required moment and duration to achieve the distinctive constancy.
The stability of a building is disturbed, when the structural subsystems are repositioned or removed. Structural systems of a building are conceived for a range of behaviour, of combined profiles of stresses for Tension, Compression, or Torque.
Structural systems of the building seem to be well integrated, because by being together they achieve constancy, which is fundamental to a structure’s being.
NON STRUCTURAL SYSTEMS
Non structural systems of a building apparently have no or very little role to play in the constancy of the building. Subsystems within a building that do not affect the constancy of a building may be called non-structural systems, such as the partition walls, doors, windows, finishes, etc.
Non structural systems though useless in structural sense, are not totally dispensable. Many non-structural systems protect the structural elements, like plaster, walls, claddings etc. Some non=structural systems achieve their own stability by depending or subsisting on the structural systems, such as tensile forms like the stretched net or a sail. Non=structural systems need not be integrated with the structure, so are replaceable or relocatable.
TYPES OF NON STRUCTURAL SYSTEMS used in a building:
1 Protective systems: Ones that cover the structural systems and non structural systems, e.g. plasters, waterproofing, roofing.
2 Filler systems: Those that fill up the gaps or spaces between structural subsystems, e.g. non load-bearing walls, joints.
3 Independent systems: These are complete systems by themselves that independently provide peculiar functionality, e.g. air conditioning, illumination, communication.