Autodesk
Revit ifc floor export issue
Hello,
I have an issue with floor quantities exported from Revit to IFC. In Revit the floor was created as a one instance (multiple regions). After exporting to IFC the area of each floor subelements equals to the total area of all subelements together. Any ideas how it can be solved?
This is a known issue in some cases, as the quantities are copied from the main Revit element. In general, we don't really want IFC to be doing calculations - IFC should be reporting what is in the Revit model. In this particular case, IFC export code will need to do some calculations, and it is in our backlog. Ideally, though, if you care about the quantities, it would be best to model the floors separately in Revit - that way, there is a 1-1 correspondence between a Revit element and an IFC entity, which means that the IFC file is more closely aligned to the Revit model. To be clear - Revit should calculate the quantities correctly in the 1-to-many Floor to IfcSlab case. But it is likely better practice to actually split up the floors, which would have the side effect of getting the right calculations.
Shouldn't the floor be exported as one element, instead of separate floors for each region? This way the area and volume will always be correct. I have the same issue btw ...
I believe there was an original intent that an IfcSlab would consist of one connected piece, not a series of unconnected objects. Finding that document from the 2000s is another matter... so you could export it as one element, but it might cause trouble given that conceptually it is really separate things.
It was also addressed in 2018: https://github.com/Autodesk/revit-ifc/issues/48 when the behavior of the exporter changed from R2018 and R2019, from one element, to a collection of separate elements. At the end, the division (for slabs as well as for ceilings) of such regions is necessarily and justified because they are not only conceptually but also physically separate things.
Multilayer slab export is based on MVD specifications. Revit has been certified for IFC2x3 CV2.0 and IFC4 RV1.2. Differences in versions are based on updates/changes due to certification testing and results.
As for the area calculations, there needs to be a determination whether this is due to a value from Revit at export OR if Solibri is doing this upon reading the IFC file.
I have tested this in various programs and I haven't found a way around this. With large complex floors we really need the ability to export floors with multiple boundaries.
Since the choice was made to no longer export multiple boundaries as one element, it should have been complemented with the correct area calculations. This is a regression in functionality and breaks an important feature in Revit. I do agree that the IFC exporter should not calculate, if that is the conclusion, the feature change should be reverted so those subparts not being chopped up but exported as one element, as intended by Revit.
We did some work to clean up quantities so I will expedite this item to see why floors don't behave properly (or report back if they should now).
