All the Building Information Models (BIMs) created during Build LONDON Live were submitted as IFC (Industry Foundation Class) files as well as in their native file formats.
The teams used more than 50 multi-discipline applications, and of these over 90% had IFC capability and were interoperable.


Interoperability implies that a BIM created by CAD system ‘A’ can be opened by CAD system ‘B’ and in this context interoperability has been available and working for many years via DXF, DWG and IFC. The majority of CAD applications (in 2010) can read all three file formats, and in almost all cases when models are exchanged the defined layers will be transposed.


With DXF/DWG file exchange, the intelligence defined as attributes for construction parts such as windows, walls, doors, components etc. is lost when the file is exchanged between different CAD vendors. But with IFC, the information defined in the BIM is transportable between applications. It is the interoperable retention of intelligence that sets IFC apart from other file formats.

However, the importance of interoperability is the ability to exchange and merge data between disciplines within the chain, more so than simply being able to swap data between the one architectural modeller and another.


Interoperability between CAD systems continues to improve in terms of robustness and functionality. At the base level it is now possible for any CAD system to read/open an IFC file from any other CAD system as a context model. At an advanced level it is now possible through interoperability to read in IFC objects from Modeller A and have them available as parametric parts in Modeller B.

Tekla structures are an exemplar of the rule with a tool that converts the IFC objects imported in reference models into native Tekla objects. Nemetschek Allplan is able to parameterise IFC's from a number of modellers including ArchiCAD and EliteCAD AR.

The image above shows how a Revit BIM was exported (by team Ryder) as an IFC and then imported into EliteCAD AR. Not only has all the intelligence been retained, but EliteCAD's parametric routines can be applied to the parts. True interoperability.

Interoperability spans the disciplines making it possible for any of the architectural modellers used during BLL2009 t to read IFC data from any of the M&E or structural modellers, and vice versa.


On any given project, fewer than 5% of the stakeholders involved will have access to a 3D CAD system, and even less will have the knowledge of how to use one. When 2D drawings were the primary means of communication this was not an issue, but now that more projects are being created in 3D, specialist viewers are required to view the design and engineering.

There are many excellent IFC viewers available that are free to download and use at no cost whatsoever. However, none of them has the ability to merge more than one file (model) together, and since a BIM will consist of several disciplines (architectural/structural/M&E), this is a notable limitation.

Other 'viewers' convert IFC's into a bespoke file format that can be opened using the developer’s free-to-use viewers. Although there is no cost of use and they may be widely and freely distributed, there is normally a high cost of publishing:

These viewers offer substantial added value by enabling the IFC file to be used for advanced applications such as time-lining (4D), clash detection, intelligent model checking and for quality presentations. Most importantly, Navisworks and Solibri allow a number of IFC's to be appended into a single multi-discipline model, without which a full BIM cannot be viewed.


One of the benefits of IFC and interoperability is that clients can own and use their data without being tied to one software vendor, engineering company or design consultant. IFC also affords a migratory path should a client wish to change from one system to another.

Interoperable software - Build LONDON Live

BIM in Graphisoft (top) exported to IFC

BIM in Revit (top) exported to IFC

BIM in EliteCAD (top) exported to IFC

BIM in Allplan (top) exported to IFC