Building Information Modelling (BIM) covers geometry, spatial relationships, light analysis, geographic information, quantities and properties of building components, project management and post-construction facilities management.


BIM data can be used to illustrate the entire building life-cycle, from cradle to cradle, from inception and design to demolition and materials reuse; quantities and properties of materials, which can be easily extracted from the model; and the scope of works, including management of project targets and facilities management throughout the building’s life. Furthermore, systems, components, assemblies and sequences can be shown in relative scale to each other and, in turn, relative to the entire project.

The Government’s Industrial Strategy, published in early 2013, states that £40 billion of public money is spent on Centrally Funded Public buildings, every year. From this, millions of pounds are lost through poor integration and not learning from past mistakes. The strategy suggests that:

  • 30% of the construction process is rework
  • 60% of the labour effort is wasted
  • 10% loss is due to wasted materials
  • 3-5% of the construction turnover is wasted due to loss of interoperability.

It follows that construction information is, therefore, often:

  • Inaccurate
  • Incomplete
  • Ambiguous.

By 2025, Government is aiming to maximise efficiency in the construction industry through legislation and best practices aimed at:

  • Lowering costs
  • Speeding delivery
  • Lowering emissions
  • Increasing exports.

Early BIM demonstration projects have already achieved savings of around 20% during the construction phase, with some on course to make 33% savings over the life of the building; future projects are targeting even greater savings.

However, BIM goes beyond simply switching to new software. It requires changes to the definition of traditional architectural phases, more data sharing than architects and engineers are used to, and a willingness to embrace partnering in an approach that collects all project related information digitally. BIM is able to achieve this by modelling representations, specifications, and the critical paths of actual parts and components used in the construction process, representing a major shift from traditional computer aided design.

The interoperability of the model requires that drawings, master building specifications, standards, regulations, manufacturer product specifications, cost and procurement details, environmental conditions (emissions data), critical paths, clash detection and submittal processes all work together. The whole process is about disparate information resources feeding into a central store of digital documentation, which then becomes the heart of the building information model.

BIM is far more than 3D CAD modelling; it is a rich information source containing geometric, visual, dimensional, and process information. If the software is the interface to a building information model; rich information content is its body and soul. Managed BIM will reduce the information loss associated with handing a project from design team, to construction team and to building owner/operator, by allowing each group to add to, and reference back to, all information they use/create during their period of contribution to the BIM model. To put it simply, without the embedded information, BIM is little more than 3D pictures.

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How does BIM work?

Building Information Modelling can, of course, still produce drawings, but the process is no longer focussed on lines, shapes and text boxes; it is now based on data sets that describe objects virtually, mimicking the way they will be handled physically in the real world. The real difference that BIM offers, however, is that it is a truly interoperable system, offering full integration, allowing the inputs of the various professionals and specialists involved in every stage of the life-cycle to work together, without data or process conflict.

Depending upon the perspective of approach to BIM, it can relate to lots of different things:

  • To an engineer – energy consumption
  • To a contractor – buildability
  • To a client – useable space
  • To a manufacturer – product maintenance, servicing, product performance.

On a technical level Industry Foundation Classes (IFC or ifcXML) is an open specification for Building Information Modelling; they are effectively an object-based file format tied to a specific data model. IFC was originally developed by building SMART to facilitate interoperability in the architecture, engineering and construction industries, and forms a commonly used collaboration format in BIM projects.

Green Building XML (gbXML) is a schema specifically focused on green building design and operation and is used as the input in several energy simulation applications; gbXML powers a number of building energy simulation tools available to the market.

BIM for existing buildings

Laser surveying and cloud points can replace the need for traditional 2D surveys, delivering accurate models of existing buildings and infrastructure as 3D models. This can also be achieved faster, with a greater accuracy than traditional methods reducing overall project costs.

3D laser scanning has been around in the offshore sector for many years, creating accurate ‘As-Built’ models of oil rigs and plant facilities. However it is only in the last couple of years that the technology has been cost effective to use in the built environment sector.

While there have been attempts at creating a BIM for older, pre-existing facilities; trying to model a standing building or structure requires numerous assumptions about building design standards and codes, construction methods and materials available at the time of construction. These factors should be borne in mind before undertaking a 3D survey of an existing structure.

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