How would one change the thickness of all these IfcWallStandardcase in this IFC file from 38mm to 40mm?
Would solidify yield trustworthy results? And how to check if all the walls are 38mm in the first place?
Wall thicknesses may be parametrically defined using IFC material layer sets. If the wall type has a material layer set, just change it there and all walls will follow suit.
@Coen I opened your IFC file, the walls are not 'typed', that is, they are not attached to an ifcwalltype definition. So I don't think you can change them globally like you're asking.
I'm not sure this would work, but you might be able to create a new ifcwalltype, and apply that new type to the geometry of the existing walls. The spring point, however, by which the grows/shrinks might be inconsistent, however.
That file, produced in Revit 2011 (That's old!) is technically invalid since as @theoryshaw says the walls do not belong to a wall type.
That said the walls do share layers akin to how types should share layers. So in theory you should be able to edit the model and have it "just work".
However, that model has a lot of junctions, and the current wall geometry generation functions ... needs a lot of improvements. So it fails on some math cases. It's been on the TODO list for a while to do a big rewrite of this aspect of the code and @qwiglydee was meant to start on an aspect on it a month or so ago but unfortunately there were complications outside our control.