CAD
means Computer Aided Design which is so vague as to be virtually indefinable,
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
Modeling 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 Modeling 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 modeling solutions have three
characteristics:
- They
create and operate on digital databases for collaboration.
- They
manage change throughout those databases so that a change to any part of the
database is coordinated in all other parts.
- 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 Modeling
I find it helps to think of BIM as Building
Information Management rather than modeling. 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, and
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.
