I decided to write this post for a certain family member of mine in the construction industry who needs to be able to talk about BIM/Revit, but doesn’t really need to know all the little in’s and out’s of it. So here’s my list:
- Understand the differences between BIM and Revit – What is BIM? What is Revit? I tried to explain this by saying BIM is to CAD as Revit is to AutoCAD. I really thought that would have cleared it up but, alas, it didn’t. So, first I’ll say that BIM, or Building Information Modeling, is the overall process of creating a three dimensional database, in the form of a model of information that pertains to the design of a building. Notice a few things in that definition: first, I used the words that make up the BIM acronym. Here’s the sentence again: BIM is the overall process of creating a three dimensional database, in the form of a model of information that pertains to the design of a building. Second, notice that I never used the word Revit. Under this BIM umbrella, there are many software applications that lead to an efficient design of space. While Revit just so happens to be one of them, it is just that, one of them. Revit can certainly be considered the main application under the BIM umbrella, but other applications are designed to perform certain functions which Revit either has minimal functionality to do, or, cannot do at all. For example, other BIM applications include Ecotect and Green Building Studio which are designed to test the efficiency of a design with regards to the environments impact on it and it’s impact on the environment. Navisworks, another BIM application, brings building information models from various disciplines together in a single environment to see how the physically interact allowing designers to make necessary adjustments before construction begins. And there are more but, for the moment, see the image below to understand it a bit better.
- Be aware that there’s more than one discipline version of Revit – If you have a keen eye, you’ll notice in the image above that I list Revit three times with different disciplines. This isn’t wishful thinking, there are three different discipline versions of Revit. Each one has tools geared to that particular discipline. Fortunately, however, all three have been designed to speak the same language and therefore a model created in one can be inserted into the modeling space of the others. The typical process of multiple disciplines working together in Revit is as follows:
- The Architect will begin building the design model in Revit Architecture.
- At an agreed upon time, the Architect will send his model to the Structural and MEP Engineers.
- Each discipline will link the architecture model into their own work space within the discipline version of Revit of their choice (i.e. Revit MEP or Revit Structure). When I say link, I mean that they are telling their own discipline versions of Revit to connect to the model that the architect sent and show it graphically within the same space.
- Once linked in, each discipline will begin their own work inserting, for the Structural Engineers, beams, trusses and columns and, for MEP Engineers, ducts, pipes and electrical connections.
- Next the engineers will send their individual models back to the Architect (without the model that the Architect originally sent to them).
- The Architect will link each model into his architecture model, and they will show up in their correct locations. Additionally, all objects that the engineers created will contain all original information inserted within them.
This process will continue on a regular schedule allowing each discipline to continually have up-to-date information.
- Be aware that there’s more than one year and number version of Revit – Each year, Autodesk (the makers of Revit) come out with an updated version of Revit. For example, the current version of Revit is 2011. As the year goes on, Autodesk will release small updates that fix little problems that have come up over time (and were reported to them by users) as well as new features they have been developing. Every time these updates are released, what is called a build number is added to the end of the version of Revit. For example, the current build of Revit is 20100903_2115. All interested parties (i.e. people who will need to either view or work in the model) will need to have the same year and build version of Revit. These numbers are consistent from Revit Architecture to Structure to MEP. The other reason this is important is because once saved in the current version, the model CANNOT be saved down to an earlier version.
- Understand that there are no such things a Revit drawings – When a project is AutoCAD-based, each individual file is a drawing file. Therefore you can ask someone, “can you send me the drawings in AutoCAD format?” With Revit, if you require all information about the project, you’re more likely to ask for the Revit model. If you need individual drawing sheets, you can still ask for AutoCAD drawings. You could also simply ask for PDFs of the drawing sheets. If you are working in Revit and someone asks you for drawing files, you can extract from the model individual, or a complete set, of drawing sheets in AutoCAD or PDF format.
- Understand that an AutoCAD-based project uses many files while a Revit-based project uses, in most cases, a single file – AutoCAD-based projects are typically set up by having individual files representing individual drawing-types (i.e. plans, sections and elevations) inserted into individual files representing individual drawing sheets. If you extrapolate that out for a large project, you can imagine the possibility of having many, many files. Revit-based projects, on the other hand, tend to be a single model file within which specific-drawing types are set up as views of that model. Additionally, within that same file, sheets are set up with those views placed on them. Since all of these views and sheets come from the single model, you can make changes to that model in an view (or sheet), and that change will show up everywhere else (thus the phrase, “a change anywhere is a change everywhere”). With all information in a single Revit model, Revit project files tend to be fairly large which is why to work with Revit efficiently, more powerful computers are required.
- Understand that while working in Revit, you’re working in both two dimensions and three dimensions at the same time – When you click the wall tool, for example, in Revit, you indicate it’s length, width and height simultaneously. Even if you’ve created the wall in a plan view, if you switch to a three dimensional, section or elevation view, you will see that the height is also represented. This is the case for all types of objects in Revit. I mention this because often times you might hear someone say (or even be the person to say it), “we don’t need to use Revit because we’re not doing any work in 3D.” This is really a misnomer because, “working in 3D” doesn’t just mean creating renderings and animations. If you are creating plans, sections and elevations, you’re working in three dimensions. Period.
- Understand what BIM Standards are and that they’re contained within template files – When an office decides to use Revit as their standard platform, they choose various graphical settings, known as standards, which dictate how, in most cases, drawings look when they go out the door. Some examples of these settings could be line thicknesses (or line weights), text fonts and font sizes, title blocks and scales (i.e. 1/8″ = 1′-0″ for plans and 3″ = 1′-0″ for details). When a new project is started in Revit, the person in charge of BIM efforts for that project will use a file (typically set up by an offices’ BIM Manager) which contains all of these settings. This file is known as a template file. Often times, you will be asked for your offices’ BIM Standards. If you do not have them documented, you can send your template file instead as 99% of your BIM Standards are contained within it.
- What year and build version of Revit is this project using?
- Remember, all parties need to be using the same year and build version of Revit so that everyone’s data can be exchanged easily.
- Is there a specific template file, and therefore BIM Standards, being used that all parties should be conforming to?
- If you are not coordinating the efforts of all interested parties, and therefore don’t have a template file containing BIM Standards you’d like everyone to use, it is likely that whomever is filling this role does have one. It is helpful to get and use this template as a starting point for your Revit model to ensure an easy transfer of data from you to whomever you might be sending your data to.
- Has a Revit model been started and can we use it as a basis for our work?
- An existing model will give you a head start on your own work because you can bring it into Revit and use it as a host for what you need to put into it, be it additional design work (i.e. a curtain wall), an HVAC system or a structural system.
- If there isn’t a Revit model built, do you have AutoCAD drawings you can send?
- Even if a Revit model has not be built for the project, AutoCAD plan drawings can be inserted into your Revit model to be used as a background for you to model off of.
- What is the schedule for uploading and downloading BIM data?
- Establishing a schedule for the exchange of data will allow you to establish more realistic deadlines.
- How often will BIM Coordination meetings be scheduled?
- Regularly scheduled BIM Coordination meetings, possibly even weekly, will allow all interested parties to continually ensure that their part of the design works well physically with the rest of the design.
- Will Navisworks be used for 3D Coordination?
- As previously stated, Autodesk Navisworks is a software application that can bring together 3D models from multiple applications and analyze how they physically interact looking specifically for unintended clashes.
The above seven points of knowledge and seven questions should give you a basic understanding of the important points of BIM and Revit as well as an idea of what important questions you should ask to begin your work. This is just the beginning of the process and Revit Essentials or Project Manager training can only increase your ability to make good decisions when it comes to staffing, budgeting and scheduling of a Revit-based project.
Thanks a lot for this. The first paragraph cleared up my confusions so I didn't need to read on, just wanted to know the difference. "BIM is to CAD as Revit is to AutoCAD" really didn't clarify it, but the latter part of the description enabled me to understand that first statement. :)
This presentation is very well written. The format used has pointed out errors in my presentations to my clients, specifically in the area of transitional reference. The subtle differences are often assumed by industry professionals as understood, or are grouped together for speed of thought and convenience. This post repeats the relevant differences and clarifies them in a coherent manner.
Have you done the same for BIM/COBie?
For some one who just started doing social media for a Autodesk reseller, I cannot tell you how helpful this information is to me. Great breakdown of some key and essential points. Thank you so much! Feel free to write more..