Beyond Clash Detection

If you could ask the model anything, what would it be?  We will share with you what we have asked and how Autodesk® Navisworks® has answered, time and time again.  On behalf of the rest of my team at AEC Factory, I welcome this opportunity to humbly share our experiences using Navisworks to go beyond simple clash detection and ultimately generate faster, more accurate, and constructible models.

As a business development manager I am often the interface between our client and our internal technical team.  Part of the excitement in my role is that each client brings a new challenge, poses an original question, or has a unique problem.  It’s my job to react, answer, and solve.  As a value added reseller (VAR) for Autodesk, we find that many of the initial client requests are software based.  What tools are best suited to meet their specific needs?   In the case of Navisworks, the question becomes which version is appropriate for their role in the project?

My confidence in sharing the intricacies and capabilities of each tool within the Architecture, Engineering, and Construction (AEC) segment of Autodesk products comes directly from my technical team and their prowess with the software.   In fact, I couldn’t write this article without the technical insight and practical input from my technical team, especially our Technical Services Manager,  Christopher Suggs.

As an Autodesk Certified Training Center, we are required to be proficient with the software.  However, I believe our greatest knowledge has been earned through challenges we have faced working on real-world projects as modelers, detailers, and Building Information Modeling (BIM) coordinators.

Navisworks: Finding the Right Version

The three versions of Navisworks software offered by Autodesk start with the no cost reader/viewer and basic query tool that is Navisworks  Freedom.  Anyone with a relatively current computer and an internet connection can download and run this software to view and measure any published Navisworks Document (NWD) file. 

Next, we have Navisworks Simulate, which is included in the Building Design Suite Premium package or available as a standalone product. Navisworks Simulate offers a multitude of options including model aggregating, scheduling, and object animation.  If you’re into site logistics and time lining, this one is all you.

The third version, available standalone or as part of the Building Design Suite Ultimate, is Navisworks Manage.  This version is the true BIM Coordination tool.  Manage includes all of the features found in the first two flavors of Navisworks while adding the ability to run and manage clash detection and resolution from the first hit to the final resolved RFI.  The following Navisworks comparison chart offers more detail.

Figure 1: Autodesk Navisworks comparison chart

A Common MIsconception

Autodesk® Revit® is an incredibly powerful and capable authoring tool for the A, E and C industries from Schematic Design (SD) to Construction Administration (CA).  Believe me, we use and promote it—often in the face of naysayers. It’s “Interference Check” feature is great for quick checks to see if items from one file or category touch objects from another file or category.   But what if you could ask more?  What if you could drill down and clash objects with varying parametric values from a multitude of different authoring software with specific clearance criteria?  What if you could quickly test several solutions for a given situation using move, scale, and rotate tools without constraint?   What if... what if… what if...

What I’m trying to convey is this: You’re only as good as your tools, and Revit is not adequate for BIM Coordination.  It’s like bringing a knife to a gun fight, and as you may or may not know, BIM coordination often mimics this analogy.  Project teams relying on Revit in this manner are not able to fully see conflicts and design issues or quickly test possible solutions as they could if they were using a purpose-built tool such as Navisworks Manage. 

Figure 2: Clash Detective vs. Interference Check

Begin with the End in Mind

Does a clash-free model really mean no clashes?  And more to the point, does it mean the model is buildable?   Running basic clash detection involves clicking the “Add Test” button, selecting two appended models, clicking “Run Test,” and then popping through one result at a time.  This is where we all started as “noobs,” but it’s not enough to achieve a clash-free, or even a clash-minimal, model.  It’s comparable to Revit’s “Interference Check” feature with a leg up given the extra reported data per clash and built-in management tools within Manage.  Navisworks isn’t the most intuitive software at first and it relies on the human element for success. 

We have found that selecting objects by parameters they contain (ala “search sets”) is mandatory to truly deliver viable and goal specific clash report results such as structural members of a certain size, shape, material, and so on.  In a project where the steel is spec’d to be monocoated the structural detailer is typically not required to model this material as it is not within his/her scope.  How do you truly coordinate to what is not modeled?   In this case we use the “Clearance” setting within the Clash Detective to create a non-modeled buffer around modeled objects.  If the neutral zone is violated, we get a big red hit! 

Tests like this are the heart of what a coordinated BIM model strives to be.  By “beginning with the end in mind” and taking this clash detection tool beyond the basics, we drill down until we hit gold, or pyrite as the case may be.  This protocol has become a standard operating procedure for us and literarily is the difference between delivering a buildable model and wasting time and money in the field later.  Constructability reviews and constantly checking for clearance as the model evolves is imperative to protect the project stakeholders and deliver ultimate project success.

Figure 3: Clearance

Disaster Avoided

Using Navisworks to go beyond the box has proven effective on many projects and the value add it brings the construction side of project development is measurable. One notable project involved a science laboratory with complex piping systems throughout.  We began like every other project, setting up our base tests to run reports and gather data, and while flying the model we noticed something peculiar.  A non-sloping storm drain?  Could it be?  Checked its properties and sure enough, Slope = 0.00 so we set off to optimistically prove this was just a small oversight by the detailer.  How do we find all offenders quickly and without the ol’ click and read of each pipe while delivering a meaningful and useful report? 

Navisworks Manage and Simulate have these two wonderful features: Find Items and Search Sets.   When used in tandem, they allow you to build very specific queries and save them for later use.  Example: Find all whose Element Category equals “Pipes,” whose System Classification equals “Sanitary,” whose Size is greater than or equal to “3 ½,” and whose Slope is less than 0.01 (1%).  The model lit up!  We saved it as a Search Set and began another query.  This time looking for a size of 3” and under with a slope of less than 0.02 (2%).  Again, the model lit up and we created another Search Set.   Considering that Sanitary applies to all drain, waste, and vent, this was a very important catch and the design team had a detailed to-do list, with Element IDs, that took us roughly 10 minutes to produce. Had we gone back to the authoring tool, which in this case was Revit, this same investigation could have taken hours.

The greatest value to identifying this problem was the timing of it.  We learned of it during our initial due diligence fly-through of the model during the design development (DD) phase of the project, well before coordination began. 

Peeling the Onion

The question I would like to pose to Navisworks users everywhere is “Are you using Navisworks to its full capacity?”  Most of us don’t know…what we don’t know.  We, at AEC Factory are not an exception to this truth.   However, through trial and error and working to meet our customers’ needs, we have peeled some of the layers and discovered new and creative uses for Navisworks.  We encourage you to do the same. There is always more to be learned and sharing among peers is how we do that.  It is for that reason we feel so honored to write this article.  We will continue to work with our eyes wide open, looking for new solutions, learning from both our customers and our colleagues.   We welcome the opportunity to hear your thoughts, answer your questions, or offer any insight beyond this article.  Please feel free to contact us at

Kim Perelli is the Business Development Manager at AEC Factory, located in Torrance, California.  Kim is not new to the construction world and spent much of her early career working for a large mechanical contracting firm.  Kim is a published author and a graduate of the University of Southern California.  You can reach Kim at

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