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BIM Overview

Do you want to know more about BIM (Building Information Modeling) or have you ever wondered what it means? AG Jack Ward summarises the HUGE subject…


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 building, bridge, highway, tunnel and so on.

The range of BIM ‘maturity levels’ are categorised as:

Level 0: Unmanaged CAD (Computer Aided Design).

Level 1: Managed CAD in 2D or 3D.

Level 2: Managed 3D environment with data attached, but created in separate discipline models.

Level 3: Single, online, project model with construction sequencing, cost and lifecycle management information.


In the UK, the Government Construction Strategy published in May 2011, states that the ‘…Government will require fully collaborative 3D BIM (with all project and asset information, documentation and data being electronic) as a minimum by 2016′. This will represent a minimum requirement for Level 2 BIM on centrally-procured public projects from April 2016.


This requirement for the adoption of BIM in the public sector has led to an increase in uptake, meaning that the UK now ranks alongside Singapore, USA and Scandinavia (in particular Finland) in terms of BIM usage. Adoption of BIM in the UK is most common among architects and larger contractors, whilst there is less take up by services engineers, facilities managers and smaller contractors.

Characteristics of BIM

Fundamentally, the purpose of BIM is to ensure that appropriate information is created in a suitable format at the right time so that better decisions can be made throughout the design, construction and operation of built assets. It is not about creating a 3D model for its own sake, and it is not an add-on process. BIM is fundamental to the way a project is set up and run.

It centres around the creation of employer’s information requirements (EIR), which define the information that the employer wishes to procure in order to be able to develop and operate the built asset. Setting this out in a contract document ensures that appropriate information is created in a suitable format at the right time.

Very broadly, building information that might be required is categorised as:



4D (including time / programme information)

5D (including cost information)

6D (including facilities management information)

At level 2, building information models are likely to comprise a series of federated models prepared by different design teams, including model files, documents and structured data files containing non geometric information about the facility, floors, spaces, systems and components. Together these create a digital replica of the built asset that starts by representing design intent, but by handover, reflects what has actually been built and installed.

The creation of a geometric model as part of this process allows buildings to be conceived collaboratively and tested virtually, before they are built and operated for real. This should reduce the problems that are encountered in construction and occupation. See clash avoidance for more information.

These models are created from a series of objects. Each object is defined only once and then placed in the model in multiple locations as required. If the object is then changed, these changes will appear throughout the model. This makes models automatically consistent and reduces errors. See parametric modelling for more information.

The common data environment (CDE), is the single source of information for the project, used to collect, manage and disseminate documentation, the graphical model and non-graphical data for the whole project team. Creating this single source of information facilitates collaboration between project team members and helps avoid duplication and mistakes.


According to the NBS National BIM Report 2015, the most popular drawing tools are:

  • Nemetschek Vectorworks 29%
  • Autodesk Revit (Architecture/Structures/MEP) 25%
  • Autodesk AutoCAD15%
  • Autodesk AutoCADLT 13%
  • Graphisoft ArchiCAD 8%
  • Other 7%
  • Bentley Microstation 3%
  • Bentley Building Suite (Architecture/Mechanical/Electrical/Structural) 1%
  • Trimble Sketchup(formerly Google Sketchup) 1%
  • Nemetschek Allplan 0%


Jack Ward

Building Surveyor