Creating Accurate IFC Data

Hello everyone,

In this first article, I decided to talk about the IFC issue because of the problems experienced by one of the companies that I gave consultancy. First thing first, IFC in brief :)

When we look at the definition on bimdictionary;

IFC refers to a neutral/open specification (schema) and a non-proprietary 'BIM file format' developed by buildingSMART. Major BIM Software Tools support the import and export of IFC files (also refer to ISO 16739)

In other words, IFC is an open file format that allows model and data transfer between programs from different manufacturers, supporting BIM processes. It can also be regarded as how DXF works within CAD system. In contrast with what is believed here, I think it is more suitable for IFC to be used for collaboration and to support different BIM uses rather than transferring the data from one team to another, for the development process of the design. In other words, to use IFC data to coordinate the models from different disciplines or calculating the cost of the project in progress, rather than using to transfer a model designed in application X to application Y, to create the shop drawings.

It is important to notice that IFC is transferred correctly between programs (By the way, no matter what program it is, the "Export IFC" command does not create miracles unless you are able to properly configure the infrastructure behind it). I want to give you a few examples at this point.

  • When we transfer the Revit model as an IFC format, we realize that many parameters (information) are not transferred at all. When we say that the Revit Parameters are transferred from the IFC transfer interface, both file transfer takes longer, and file size increases. Apart from that, it becomes difficult to work with the IFC file (due to a large number of parameters).

Instead, if you group the parameters you want to transfer, you will get a much more manageable model.

  • Another issue is that the components not going into the proper categories. Now I can hear you all say, "We already define categories in Revit." I have two answers; the first one is that what you are expecting to transfer may not always get transferred from Revit properly, the second one is that you want to transfer the wrong thing to the right place :) A bit complicated? Let me explain with an example.

In the first picture, you see a finished floor as an example. Do you know how an Architectural Floor in Revit is transferred to IFC?

Let me answer, as a Slab! A concrete slab as you all know. However, it is possible to transfer it into the right category when proper arrangements are made in Revit.

As seen in the picture, this not only makes sure that it goes into the right category, it also ensures that the correct parameters are added to this component in IFC. Of course, apart from that, since we also understand what the element actually is, we can have rule-based checks on programs such as Solibri Model Checker, which is no longer a concrete slab, but an architectural floor.

In the second example, an element we created using the wall command can actually become a suspended ceiling component, but this will (naturally) go to the IFC as a wall. However, we can transfer this as a suspended ceiling.

  • I think another very important issue is the classification, despite not being available in Turkey. Thanks to the classification, we can perform, for instance, rule-based parametric checks on our BIM model. This allows all parties to examine the BIM model properly. But on the Revit side, we can only assign a single classification parameter under the name Assembly Code. Of course, we can determine the classification rules in our IFC control program, make this arrangement there, and query our model. But if we can do this in the BIM model itself, why should we do it again? Again, by making the correct arrangements in Revit, we can automatically make multiple classification transfers into the IFC model.

All classifications for the furniture you see in the picture have been transferred from the native BIM model to IFC.

  • Of course, there are other points that require us to do all this right. For example, we want to implement different BIM uses for our project. Let me be a little more clear (I think it will be more suitable to write here because it is a question I face often). The money issue…

  • I think it's best to come to an agreement that Revit, Allplan, Archicad, AECOSim are the systems under the "Design Authoring" section for BIM applications. These, of course, can take model-based, simple, and consistent quantities as tasks. However, I have never found it the proper way to handle the money parameter within these programs. This is the subject of 5D. Money is something that has alternatives and it constantly changes. Quantities too... Let's not go deeper into this subject at all. Depending on the level of detail and the stage of the project, something you can call a brick wall, the amount of water contained in the mortar of the brick wall in the analysis part... Anyways, shortly, I believe it is best to use a separate 5D BIM system for this. And probably this 5D system will also need an IFC model that is correct, high quality (by quality I mean, the model has been checked, meets the project needs according to the given criteria, has accuracy enough and problems have been solved).

In conclusion, no matter which BIM system you need to work with IFC (which is probably necessary to use), you might want to take into consideration what your BIM system, target system, or IFC structure supports or not.


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