(Mis)understanding BIM :-

CAD means Computer Aided Design which is so vague as to be virtually undefinable, yet we all inherently know what CAD means. The context we use it in helps to define it. BIM, on the other hand, has very little context at this point and when it does it is often confused and unclear.

What is BIM and why is the industry so confused? To answer that question it is probably easier to first define what BIM is not.

BIM is not 3D

3D alone does not give you a Building Information Modelling solution. Consider a Sketchup model - a representation of a building, project or component in 3D. There is no added intelligence to give you any “data” about the project. To understand what each element represents it is necessary for the person using the model to interpret the geometry. As soon as you add the model into Google Earth it suddenly inherits additional project information: where it exists spatially. The model has now become “BIM” (albeit simply).

Conversely, BIM does not have to be in 3D. It is quite possible to have a BIM model in 2D alone. A simple example is the use of a line and arc to represent a door. As with the Sketchup example above the lines and arcs have to be interpreted as a door. Once those elements have been put on a doors layer (e.g. A-G322-G-Door in the AEC CAD Standard) they now have added intelligence; building information that tells someone using the file what those elements represent. Taking that further the elements could be part of a block or cell with attributes (tags) added to them. This is a simple 2D Building Information Modelling concept.

BIM is not Revit

Autodesk have got a powerful marketing machine… For years now I’ve heard people tell me how they would do something in “CAD”. “What software?” I always reply. “CAD, you know, Autodesk CAD”. The same thing appears to be happening with BIM. The terms BIM and Revit are becoming interchangeable. Be aware that Revit, whilst being a BIM solution, is not BIM. Even if you use Revit you can use it without being BIM at all.

BIM is not a single database or “single building model”

This is one of the main confusions with regard to adopting BIM. A lot of people believe BIM has to be a single database from which every party extracts their information in the format they require. Even some software manufacturers describe BIM as having to use a single database in order for it to be BIM:

“Building information modelling solutions have

    three characteristics:

(1) They create and operate on digital databases

    for collaboration.

(2) They manage change throughout those databases

    so that a change to any part of the database is

    coordinated in all other parts.

(3) They capture and preserve information for

    reuse by additional industry-specific

    applications.”

Or

“The idea behind a building information model is

    that of a single repository. Every item is

    described only once. Both graphical

    documents—drawings—and non-graphical

    documents—specifications, schedules, and other

    data—are included. Changes are made to each item

    in only one place.”

It is better to think of BIM as a series of models. You may have an architectural model (in 3D), you may have a structural model (in 2D). Each of these models may be made up from a series of DGN or DWG references to allow individual access to a package of work. BIM doesn’t have to be any different to existing CAD in terms of processes and data management.

BIM is not Project Lifecycle Management

For some reason as soon as BIM is mentioned the assumption is made that “it’s only BIM if everyone in the team, from conception to facilities management is involved”. While well-managed data will improve the flow of information through the design, construction and post-construction phases, this is not a definitive requirement of BIM. Far from it; I would always recommend anyone starting down the BIM road to consider only their internal benefits in the first instance. Understand where the production “bottlenecks” occur and see if there is a BIM solution that can address them. It may be drawing or schedule production, or the dynamic linking of the two together, or any number of design processes that can be improved internally. Only once you have developed a sound working method for your project can you start to consider the rest of the office. Only once you have developed sound working procedures for your office can you start to consider the implications of including other collaborators into the equation. Take it one simple step at a time; there are an infinite number of shades of grey between black and white.

BIM is not Building Information Modelling

I find it helps to think of BIM as Building Information Management rather than modelling. Just like CAD isn’t only vector-based lines, arcs and circles, but is instead a mix of vector elements, raster images, printer configurations, plot styles or pen tables, Word files, spreadsheets, and a whole host of other hybrid formats and data, so is BIM. It’s not a single piece of software, it’s not a database, it’s not a 3D model, it’s not a particular phase in a project - although it can be all of these things.

So what is BIM?

In simple terms BIM is the management of project information, both the construction of that data and the iterative process of exchanging it. BIM is the added intelligence to project data that allows anyone to interpret that data correctly, removing the risk of assumptions. BIM is the process by which the right information is made available to the right person at the right time.