BIM
BIM stands for building information model and is a digital 3D model of a building in which every object (wall, door, column, ventilation duct) is enriched with data on geometry, material, cost, schedule, supplier and maintenance interval. The model is used as a shared working surface throughout the whole construction process, from design through manufacturing and construction to operation and maintenance.
What separates BIM from an ordinary CAD drawing is that every object has a data-defined meaning, not just a line and a colour. A wall knows that it is a wall, which layers it consists of, which fire class it has and which U-value it achieves. That lets the model be used for energy and daylight calculations, quantity take-offs, clash detection between disciplines, cost control and production planning. The standard that ties this together is IFC (Industry Foundation Classes), an open ISO standard (ISO 16739-1) managed by buildingSMART. IFC means that models from different CAD tools (Revit, ArchiCAD, Tekla, Allplan) can be exchanged without loss of meaning.
Statsbygg requires IFC deliveries in all its projects and has, together with DiBK, driven the development of Norwegian BIM requirements since 2008. The Norwegian standards NS 3457 and NS 8360 set classification and naming rules. Maturity is often described in the levels LOD 100 to LOD 500: LOD 200 corresponds to a concept design, LOD 300 a detailed design suited to a building application, LOD 400 production ready, LOD 500 as completed with "as built" data. A BIM programme (BEP, BIM execution plan) in the project defines which level of detail each discipline is to deliver, and when.
In the design phase, the architect, RIB (structural), RIE (electrical) and RIV (building services) consultants use a coordination model in which the discipline models are layered on top of each other and clashes are detected automatically. On site, the model is used for 4D (schedule linked to objects), 5D (cost), machine control (excavators that read BIM directly) and production drawings pulled from the model in real time. In operation, the model can be linked to an FDV system (management, operation and maintenance) as a "digital twin": an architecture for logging defects, planning service and tracking energy use at object level. The model then becomes the basis for decisions across the whole life of the building.
For BREEAM-NOR certification and EU taxonomy reporting, BIM is close to indispensable. Material documentation, greenhouse gas calculation (NS 3720), life cycle cost and energy calculation (NS 3031, linked to energy labelling) all draw their data from the model. BIM has also become a working tool for area calculation of UFA, BYA and use unit.
The difference between BIM and CAD is one of principle: CAD describes geometry, BIM describes objects with data. The difference between BIM and a GIS model is that GIS works with georeferenced objects on the map surface (FKB, matrikkel), while BIM works with detailed building objects with local geometry. In large projects the two are integrated (BIM-GIS) to combine building information with terrain and infrastructure. Tools such as ArcGIS and Esri's CityEngine support that link directly.
Limitations worth mentioning: BIM data is only as precise as what is actually entered. Models that are not maintained when changes are made on site quickly become outdated and misleading. Shared data storage through a common data environment (CDE) under NS 8360 is the precondition for the model retaining any value.
More information: buildingSMART: IFC, Statsbygg: BIM
English: Building Information Modelling (BIM).
Frequently asked questions
What is BIM?
Building information model: a digital 3D model in which every object has data on geometry, material, cost and schedule. Used in design, construction and operation.
What is IFC?
Industry Foundation Classes: an open ISO standard for exchanging BIM data between different CAD tools. Managed by buildingSMART. It lets models be exchanged without vendor lock-in.
What does LOD mean in BIM?
Level of Development: an indication of how detailed the model is. LOD 200 corresponds to a concept design, LOD 300 a detailed design, LOD 400 production ready and LOD 500 as completed with actual data.
What is the difference between BIM and CAD?
CAD describes geometry (lines and surfaces). BIM describes objects with data (a wall knows that it is a wall, with material and fire class). BIM is CAD plus object semantics.
What is the difference between BIM and GIS?
BIM works with detailed building objects, GIS with georeferenced objects on a map (FKB, matrikkel). In large projects they are combined through BIM-GIS integration, so you can see buildings in context with terrain and infrastructure.