Building levels



Defining different building levels is a way to analyse buildings by breaking them down into successively smaller or simpler units, e.g. into elements, components and materials. However, depending on the purpose of the analysis, buildings can be broken down in various ways, e.g. by functional, physical, legal or economic characteristics. Accordingly, a common terminology could not be developed.


Whenever the deconstruction of a building into successively smaller parts is proposed or adopted, further clarification will be indispensable. Only for the levels ‘building’ and ‘material’ could a general definition be found. The levels in-between both vary according to the purpose.

The necessary clarification should not only present the introduced hierarchy and the different levels it includes. Also, the characteristics that determine to which level a certain assembly or part belongs should be defined unambiguously.

Because of the consistent interpretation of their meaning throughout different domains, the use of terms ‘part’ and ‘assembly’ is encouraged. Nevertheless, for both terms it is useful to clarify whereof and of what the considered unit is a part or assembly. After all, every unit can be a part of a larger part and the assembly of several smaller assemblies at the same time. For instance, a window, an assembly of parts such as glass panes and aluminium profiles, is only a part of the building façade.

It is impossible to define unambiguously the however frequently used terms ‘component’ and ‘element’. If these terms would be used for one or more specific purposes, a corresponding definition should be provided in this common language.

Related terms

Building: construction providing space to persons, their activities or belongings. Generally, it is a complicated assembly of building materials.

Material, building ∼: a raw material or bulk product used to construct buildings, e.g. lime, sand, clay and cement, as well as wood, concrete, natural stone and bricks, zinc, glass, stucco, paint and so on.

Part, building ∼: a subdivision of a more complicated entity. It is advised to state of what entity the described subdivision is a part; not just “a part”, but “a part of…”.

Assembly, building ∼: a group of less complex entities. It is advised to state of what entities the described group is an assembly; not just “an assembly”, but “an assembly of…”.

System, building ∼: a group of less complex entities characterised by a specific relation describing how the constitutive parts (can) work together or how they are connected, as in ‘open building systems’.


Haslinghuis E. and Janse H. (1997) Bouwkundige termen: verklarend woordenboek van de westerse architectuur-en bouwhistorie. Primavera: Leiden.

ISO (2013) ISO 15686-11 Buildings and constructed assets, Service life planning – Part 11 Terminology. International Organisation for Standardisation

De Troyer F. and Sarja A. (1998). Open and Industrialised Building, A Review of Approaches and a Vision for the Future. E & FN Spon, London.