BIM, defined
Ask ten people in the industry "what is BIM" and you will get answers ranging from "a 3D model" to "Revit" to "a way of working." The most accurate answer is the broadest one: BIM is a process for producing and using a structured digital representation of a building. The model is the artifact; the collaborative workflow around it is the substance.
The word that does the heavy lifting is information. A line in a drawing tells you where a wall is. A wall in a BIM model knows it is a wall — it knows its height, its fire rating, its material layers, its cost, who manufactured its components, and how it connects to the floor and roof around it. Multiply that across an entire building and you have a queryable database that happens to look like a 3D model.
Process, not just software
People often use "BIM" and "Revit" interchangeably. That is a useful shorthand and a misleading one. Software is how you author and coordinate a model, but the value of BIM comes from the discipline of keeping one coordinated model that everyone contributes to and trusts — instead of a pile of drawings that drift out of sync the moment someone makes a change.
This is why the comparison that matters most for newcomers is BIM versus the drawing-based workflows it replaced. We cover that head-to-head in detail in BIM vs CAD. The short version: CAD draws a building, BIM models one.
Who uses BIM, and for what
BIM spans the whole AEC industry — architecture, engineering, and construction — plus the owners and operators who inherit the building afterward. Each role uses the same model for a different job:
| Role | What they do with the model | Typical tools |
|---|---|---|
| Architects | Author the design model, generate drawings and schedules | Revit, ArchiCAD, Vectorworks |
| Structural engineers | Model the frame, run analysis, detail connections | Revit, Tekla Structures |
| MEP engineers | Model mechanical, electrical, and plumbing systems | Revit MEP, Bentley |
| General contractors | Coordinate trades, sequence, estimate, prefabricate | Navisworks, ACC, Solibri |
| Owners / FM | Operate and maintain using the as-built model | CDE + COBie data, FM platforms |
That last row is the one people forget. A model's life does not end at occupancy — a well-built BIM model is handed over to the owner as an as-built record they can use to run the building for decades. The contractor's stake in all of this is large enough that we treat it separately in BIM for general contractors.
The dimensions of BIM (3D to 7D)
You will hear people talk about "4D BIM" or "5D BIM." The dimensions are a shorthand for the kinds of information layered onto the geometric model. 3D is the model itself; each higher dimension adds another data layer:
- 3D — the geometric model: the coordinated shape of the building.
- 4D — time: linking elements to the construction schedule to simulate and sequence the build.
- 5D — cost: tying quantities in the model to pricing for live estimating.
- 6D — sustainability: energy and performance analysis (definitions vary — some teams use 6D for facility management).
- 7D — facility management: the as-built data the owner uses to operate the building.
The numbering above 5D is not standardized — teams disagree on whether 6D means sustainability or facility management — so always confirm what a contract means by a given dimension. We break each one down, with that ambiguity addressed honestly, in BIM dimensions explained.
BIM levels and maturity
"BIM levels" describe how mature and collaborative a project's BIM use is — originally a UK framework that became a global reference point:
| Level | What it means |
|---|---|
| Level 0 | Unmanaged 2D CAD. Paper or digital drawings, little to no collaboration. |
| Level 1 | A mix of 2D and 3D, managed in a shared space, but models are not exchanged between disciplines. |
| Level 2 | Each discipline maintains its own 3D model and shares them in a common format (such as IFC). Coordination happens federated. The most common target on serious projects today. |
| Level 3 | A single, fully integrated shared model with real-time collaboration. Largely aspirational. |
In practice the industry has shifted toward the language of ISO 19650 — the international standard for managing building information — which talks about information management rather than numbered levels. But "Level 2" remains the phrase most owners use when they specify what they expect.
The software landscape
BIM is a category of tools, not one product. The main families:
- Authoring — where models are created: Autodesk Revit, Graphisoft ArchiCAD, Tekla Structures, Bentley OpenBuildings, Vectorworks.
- Coordination & clash detection — where discipline models are combined and checked for conflicts: Autodesk Navisworks, Solibri.
- Common Data Environment (CDE) — where the project's information lives and is shared: Autodesk Construction Cloud (formerly BIM 360), Trimble Connect, Bentley ProjectWise.
- Open exchange formats — IFC, the vendor-neutral model format from buildingSMART, and COBie, the standard for handing over asset data to owners.
Why BIM matters
The payoff of BIM is fewer surprises. Conflicts between trades get caught in the model instead of in the field. Quantities come straight off the geometry instead of being counted by hand. The schedule can be rehearsed before a shovel hits dirt. And the owner ends up with a digital record of what was actually built. None of that is free — BIM demands upfront modeling effort, coordination discipline, and skilled people — but on complex work the alternative is more expensive in rework, change orders, and disputes.
Common questions
From here, the natural next steps are the comparison every newcomer needs — BIM vs CAD — and the data layers that make BIM more than a 3D picture, in BIM dimensions explained. For the broader software picture, see digital solutions for contractors.
- BIM
- Building Information Modeling — the process of creating and managing a shared, data-rich digital model of a building.
- CDE
- Common Data Environment — the agreed single location where project information is collected, managed, and shared.
- IFC
- Industry Foundation Classes — an open, vendor-neutral file format for exchanging BIM models between different software.
- LOD
- Level of Development — a scale (100–500) describing how detailed and reliable a model element is.
- COBie
- Construction Operations Building information exchange — a standard for delivering asset data to owners for facility management.
- ISO 19650
- The international standard for managing information across the lifecycle of a built asset using BIM.
- Federated model
- A combined model assembled from separate discipline models that remain individually owned and editable.