Fabrication for Revit MEP - 5 Years In

This is a follow-up to the article with the similar title published a year ago. It’s always been one of my favorite things about Autodesk® Revit® MEP—that the developers really are working on improving our experience with each release. The Fabrication feature set in Revit 2017 is an example of that continuous incremental improvement. If you’re especially curious, you can find that previous article in June 2015 AUGIWorld (

We Revit users spend most of our efforts digitally, generating content for models and drawings, reviewing PDFs, responding to RFIs. After putting so much effort into the digital version of a building, I don’t know any designer who is happy with the idea that the builders and fabricators just set aside these drawings and start over. We all want to see a more direct translation of our effort into the actual building components.

In October 2011 Autodesk announced the purchase of MAP Software, taking a big stride toward that goal of direct translation to fabrication data.  However, much of my previous review was spent pointing out how far they still needed to go.

Here is the short list of functionality that I still expect in order to consider the fabrication features complete inside of Revit:  

  • Maintaining the Revit style of modeling
  • Full engineering support
  • The same ease of documentation
  • The ability to create a complete model
  • Spool drawings
  • Direct export to fabrication equipment
  • Support for robotic field layout

Just as before, this is my personal review of the fabrication software within Revit.

Revit’s Style of Modeling

There are some nice improvements and additions, which I’ll cover at the end of this section, but I’ll start with the default and most obvious method presented by the user interface. As you can see from the many available demo videos of the new fabrication features in Revit 2017 (for example or Autodesk’s own channel ), fabrication parts are not modeled in Revit in the same fashion as standard MEP elements. The modeling method for standard Revit MEP elements is strongly based on the straights, allowing the system family settings to insert transitions and bends for you. The new fabrication features default to specifically picking and placing all components. As I said, this is not the only way, just the most obvious.

For instance, here is the process to create a run of duct (aligned to another run) 15 feet long, reduce its size, run 3 more feet, turn and run another 15 feet.  This list includes every required action (See Figure 1).

Figure 1: Example duct runs

Standard Revit MEP Duct

  1. Start the Duct command
  2. Select the needed size in the Options Bar
  3. Hover your mouse in the general area to snap to remote objects and pick a start point
  4. Pick an end point (or type a distance and press Enter)
  5. Change the duct size
  6. Click a new endpoint (or type a distance) parallel to the previous run (the duct command stayed active)
  7. Click a new endpoint perpendicular to the previous runs

New Fabrication Features

  1. Select “Straight” from the MEP Fabrication Parts palette
  2. Select the needed duct size in the Properties palette (Options Bar remains empty)
  3. Pick a start point
  4. Start the Align command
  5. Pick the centerline of the remote fabrication duct (edges are not available)
  6. Pick the centerline of the new duct segment to complete the Align command
  7. Select “Straight” from the Fabrication palette again
  8. Pick to place another straight at the end of the previous
  9. Pick again for another straight
  10. Select the “Transition” fitting from the Fab palette
  11. In the Properties palette, change the “Secondary End” to the desired duct size
  12. Pick to place the transition on the end of the run
  13. Select “Straight” from the Fab palette
  14. Pick to place the straight
  15. Cancel the straight command
  16. Select the duct segment just placed (it does not remain selected after placement)
  17. To shorten that segment to 3 feet, either drag the endpoint grip in the Drawing Area or in the Properties palette, change “Length Option” to “Value” and type 3 in the Length property
  18. Select your desired elbow from the Fab palette
  19. Pick to place the elbow
  20. Select “Straight” from the Fab palette
  21. Pick to place the duct segment
  22. Pick again to place the duct segment
  23. Pick a final time for the last piece

Modify Tools

A huge portion of the Revit modeling method relates to the modify tools. These have received significant updates for Fab parts in the 2017 release.

Trim and Extend now work—with the caveat that they only work from one Fab part to another. This means that you can extend a MEP Fabrication round duct to meet a MEP Fabrication rectangular duct and it will connect and place the tap fitting between the two, as shown in Figure 2. However, you cannot use these modify tools with anything else in the Revit platform. You cannot extend a duct to meet a detail line or a reference plane. Similarly you cannot drag the endpoint of a duct and have it snap to a detail line, though oddly, you can drag and snap to a reference plane.

Figure 2: Editing tool - Extend

There is also no remote snapping function for Fabrication parts aligning with distant model elements as you drag them around; this includes even aligning with other distant Fabrication parts.  The Align tool does work; however, this takes us way back to old hand drafting and AutoCAD® style of editing, which made extensive use of temporary sketched lines for layout.

Not only are the Modify tools only partially functional, but such simple and common modification methods as changing a size or turning an elbow into a tee are not supported at all. In Figure 3 note the lack of the small plus symbol for the Fab part on the right-hand side. This means that even small changes or additions first require deleting large sections of your work and redrawing.

Figure 3: Editing tool – plus symbol missing for fabrication parts

There is a Modify tool that has been in place since the previous release and continues to be very helpful. After making minor moves, nudging a duct or pipe around, it is easy to select a large run of straights and fittings then hit the Optimize Lengths button. This ensures that you don’t have overlong unbuildable/unavailable parts and that you don’t have excessive splits into too short lengths.

Full Engineering Support

There is no change to this for 2017; MEP Fabrication parts still do not support the calculation and propagation of flow in a duct or pipe or the assignment of the system type. Systems and flow are a bit finicky and require effort to maintain in standard Revit duct and pipe layouts, but they do indeed work. If you would like a deeper discussion on doing this in Revit, and you are an AUGI Professional Member, you can review the previous article in AUGIWorld January 2012 “Plumbing Systems for Well-Documented Flow” (

Since the default Fabrication configuration files do not have any air terminals (grilles/diffusers), it would seem that the intention is for users to continue to use standard Revit family air terminals. This would still allow you to perform airflow calculations with Revit spaces with no change from the Fabrication features.  As mentioned before, the flow defined by the Air Terminal will not propagate in the Fabrication part duct run.

Ease of Documentation

Full engineering and construction documentation can be genuinely beautiful when generated from Revit.  Model elements and annotation elements blend well and all of this can be done much easier and more quickly than what I remember from my now distant AutoCAD days. 

Is this ease of documentation still available with Fabrication parts? Mostly yes. Updated for 2017 there are significant improvements in the ability to display and document your project.

MEP Hidden Line Display

In 2016 this was missing. To illustrate, the hidden line functionality was similar to using all Generic Models categories. In 2017 it works just as desired—fab parts located vertically below other fab parts even below standard Revit MEP elements are properly broken with the dashed line type below (see Figure 4). This even includes the proper display of insulation!

Figure 4: Accurate hidden line display

As mentioned earlier, systems and flow do not exist for Fabrication parts; both of these are frequently part of my documentation. This is a limitation both for design and documentation.

One unexpectedly missing documentation feature is single line display. For Revit duct, setting the view to Detail Level: Coarse will turn it to single line, both Medium and Coarse show pipe as single line. This is often useful for particularly small scale plans. However, this cannot be done for MEP Fabrication duct or pipe parts. There doesn’t seem to be any way to get single line display either through manipulation of detail level or visibility graphic overrides.

A Complete Model?

There is no significant change to this item’s level of functionality in 2017. When talking about Revit, one of the more common statements is that the key to success is good content. Even though in the first release of Fabrication in Revit, there did seem to be plenty of content to use.  However, if there are some minor modifications needed, there is no fabrication configuration editor.  You can download the default configuration from Autodesk or receive a configuration from a current CADmep user.  For instance, if you want to change the default cast iron no-hub elbow from quarter bend to short sweep, there is no way to do this within the Revit interface.

One of most useful things in Revit is the family editor—both stand alone and in the context of a project for in-place families.  There are times when the parts needed are completely custom.  Imagine a duct fitting that can only be built by hand in the corner of the shop by the old school tin knocker.  This fitting may not be in the pre-created list of Fab parts.  Because Fabrication Parts are not Revit families, they can’t be customized or built from scratch in any version of the family editor.

Fabrication Parts are not Revit families, which significantly limits their customizability.

Spool Drawings

There is no change to this functionality in 2017. A spool drawing is one step between a contractor’s building scale shop drawings and the purchased part list/fabrication cut and bend drawings.  Usually it represents a handful of parts that are going to be assembled in the shop and shipped to the job site.  This might be a pre-assembled handful of duct fittings or welded pipe and fittings (see Figure 5).  This has been supported for some time by the Revit platform feature “Assemblies.”  However, it will be important for the final plan set to be careful that individual parts are identified by the same parameter throughout the manufacturing and assembling process.  For instance, if the “Mark” parameter is used to tag piece numbers, you will have your fabricator confirm that the ID is also visible in his software and will translate to a physical label on the part. 

Figure 5: Assemblies as spool drawings

Some information about Fabrication parts is not available for use in Revit schedules (i.e., duct connection types).  This will again require additional care with regard to coordinating between information-rich sources such as the exported fabrication file .maj and somewhat poorer sources such as Revit schedules and tags.

Direct Export to Fabrication Equipment

Modeling with fabrication-ready elements would be nearly pointless if we couldn’t plug that information directly into CAMduct for use in cutting and folding the sheet metal. New for 2017, this is automatically installed, but it shows up under the Add-Ins ribbon instead of the Systems tab, being obviously related to any of the other Fabrication functions. The “Revit Extension for Fabrication” will allow you to directly export to the .maj file format. 

What about in-direct exports? Many installing contractors own their own fabrication equipment, but others buy fabricated parts from multiple sources.  The best way to do this may be with the same .maj file, but if the supplier uses different software to drive their equipment, a different method may be needed. The lowest common denominator is a simple list of parts with enough data to get the correct size and shape.  As mentioned above under Spool Drawings, this data is lacking the required fields available to be scheduled with Revit Fabrication parts.

Support for Robotic Field Layout

Again, there is no change to this functionality in 2017. Using a robotic field layout tool is the best way to translate your carefully BIM coordinated layout to actual locations in the building.  The one common method for accomplishing this in Revit is to add a nested “point” family to your various hanger families (see the blue highlighted elements in Figure 6). As already covered, Fabrication Parts are not Revit families.  This being the case, some other more manual method of identifying and exporting hanger locations will have to be devised.

Figure 6: Point layout elements embedded in Revit family


I can’t help but continue to be surprised at the Autodesk’s overall strategy for MEP Fabrication Parts. The power of Revit MEP has always been in its fully parametric System and Component families. However, when it comes to fabrication, they are instead using the previous AutoCAD-based .itm files from CADduct and gradually polishing some of the ugly spots.

For my own production fabrication modeling needs I still don’t use Autodesk’s MEP Fabrication Parts, and instead use an add-in. That product, SysQue, is far closer to what I’d always expected from the union of Autodesk and MAP Software five years ago.

Competition between the players helps drive the whole industry forward, and I will continue to watch the sometimes gradual and sometimes transformative steps in this area of our industry with tremendous interest.


Two New Features  

Two new features that are a significant improvement are Design to Fabrication and Route and Fill.

To use the Design to Fabrication feature, model a run of duct or pipe (conduit and cable tray not supported) and click the Design to Fabrication button. Then just select the fabrication service desired and it’s converted automatically. This means that for the numbered lists above, if you used this conversion feature, you can create the run of duct with Revit system families, and convert to Fab parts with a single click.

To use the Route and Fill feature, select a fabrication part with an open end, click the Route and Fill button, then select any other compatible fabrication part, also with an open end. The tool is very intelligent and offers multiple routing options that can be scrolled through—or even better, select the checkbox to choose the specific fittings desired.


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