What is BIM
the methodology, not the software

BIM (Building Information Modelling) is a methodology for creating and managing a construction’s information in a three-dimensional model connected to a database. It is used to design, coordinate and detect clashes between disciplines before building, to plan works and costs, and to maintain the asset throughout its service life: each element in the model — a wall, a pipe, an item of equipment — carries its real data (material, dimensions, specifications); it is not just a drawing. In a plant that is already built, BIM also provides a faithful copy of what exists, on which to decide any intervention.

BIM is the methodology; Revit is one of the programs used to apply it. BIM defines how a construction’s information is organised and shared; Revit, from Autodesk, is one of the tools for creating that three-dimensional database model. Put another way: Revit is to BIM what a word processor is to writing. You can do BIM with Revit, ArchiCAD, Allplan or other programs; BIM does not depend on a single piece of software.

The most widespread BIM tools are the modelling programs — Revit (Autodesk), ArchiCAD (Graphisoft), Allplan (Nemetschek) or AutoCAD Plant 3D for industrial facilities — and those for model coordination and review, such as Navisworks or BIMcollab. To exchange models between different programs, the open IFC format is used, a standard that stops the model being trapped in a single piece of software. In the digitisation of existing plants, the laser scanner is added, which captures the real geometry before it is modelled.

A BIM model is the three-dimensional representation of a construction in which each element is an object with associated information, not a mere line or colour. The model knows that an element is a pipe of a specific material and diameter, or an item of equipment with its specifications — it does not merely show its shape. This information makes the model searchable, measurable and isolable by system, and useful for making decisions about the real construction.

BIM modelling is the process of building the model by recognising each element with its real properties, not just its geometry. In new builds, the model is built from the design; in an existing plant, A3D models on the point cloud from the laser scan, reconstructing what the laser measured: structures, equipment, pipes and ducting as they stand, with their real geometry — even non-orthogonal — and their data.

Modelling in BIM means creating each element as an object with data, instead of drawing 2D lines as in traditional CAD. When modelling in BIM you do not “paint” a shape: you define an element that the model recognises (a wall, a valve, a tank) with its properties. In as-built capture, modelling in BIM is faithfully reconstructing, on the scanner’s measurement, the plant that already exists, so that the model matches reality.