BIM dimensions

Building Information Modelling (BIM) is a very broad term that describes the process of creating and managing digital information about a built asset such as a building, bridge, highway, tunnel, and so on.

Very broadly, the types of building information that might be required in a model can be described as ‘dimensions’. Initially this referred simply to the distinction between 2-dimensional computer aided design (CAD) information and the 3-dimensional information in BIM models, but it then extending to include other information that might be needed to managed the design, construction and operation of built assets.

In general terms, there is a broad consensus that the following dimensions can be included in a model:

2D. Two-dimensional graphical information.
3D. Three dimensional graphical information.
4D. Time and programme information.
5D. Cost information.
6D Facilities management information.

However, there is some ambiguity in these definitions, and alternative descriptions are sometimes used.

In an article in 2018, Richard Saxon CBE (associate director of Deploi: BIM Strategies) suggested that definitions of dimensions were ‘hazy’ and called for conventions to be developed, saying ‘…it should be based on the logic of what a dimension is. It’s not about policy or outcomes, it’s about a particular view of the data in the model.’

He suggested that the first five dimensions were relatively fixed, but beyond that, he proposed:

6D: Operational and maintenance information.
7D: information flowing from the building, explaining this as; ‘The cube of six dimensions define what the built asset is “about”, but the seventh is information “from” the sensors and analytics which increasingly help to commission and run the asset.’