3D Building Information Modelling

Building Information Modelling is a way of designing where the model carries the information, not just the geometry. Every element knows what it is, what it is made of and how it relates to what it touches, so the drawings, schedules and quantities are read out of the model rather than drawn separately and reconciled afterwards.

On public works, yes, and the threshold keeps falling. Projects above one hundred million euro have been in scope since January 2024 and projects above twenty million since January 2025, with the mandate widening further to 2027. On private work it is not required, and it is increasingly asked for anyway, because the client benefits are the same either way.

Level 2 is where each discipline models separately and the models are then federated and checked together, to a shared set of standards and naming conventions. What it requires in practice is agreement before modelling starts: who models what, to what level of detail, in what format, and where the files live.

It is an automated check for elements that occupy the same space, run through each other, or leave no room to be installed. Models are exchanged, combined and tested against rules and tolerances, and what comes out is a list of conflicts with a location each. Every one resolved in the model is one not resolved on site with a drill, which is where the saving actually is.

It is the structural, civil and building services models brought together into one coordinated whole, without merging them into a single file. Each discipline keeps ownership of its own model and the federation is what everybody checks against, which is how coordination happens without anyone losing control of their own design.

IFC is the open format models are exchanged in, so a model authored in one package can be read in another. It matters because it is what keeps a project from being locked to one vendor's software, and it is the format clash detection and most client handover requirements are built on.

It is the single place the project's information lives, with one version of each file and a record of who changed what. Without one, coordination becomes a question of whose copy of the model is the current one, which is a question with no good answer once there are three of them.

That is most of the point of modelling properly. Bills of quantities, take off tables, bar bending schedules and CNC files can all be generated from the model, which means they agree with the drawings because they came from the same source. Where the model is complete enough, procurement and cost estimation get a great deal more reliable.