A Practical Approach to BIM/VDC - Spatial Allocation

/// By Matt Edwards
Traditional 2D design workflow previously involved drawing detailed sections that forced us to physically look at spatial allocation. As processes have become more automated, design teams have begun to rely on each other for coordination. This has a tendency to remove the planning process at the beginning of the job, where spatial allocation was previously addressed.

Spatial Allocation is simply a fancy term for identifying space in a BIM model for disciplines to route their systems.  Generally, this is achieved by using “No Fly Zones,” which are transparent boxes that are laid out prior to routing any systems.  This step is a crucial part of the design process that avoids spending extra time and money trying to fix coordination issues throughout the design phase.

The following is a recommended workflow to incorporate spatial allocation back into projects:
  1. Spatial allocation should be the first step in the MEP modeling process. 
  2. The design team should identify areas of risk; i.e., long corridors or areas with limited ceiling space. 
  3. Agree upon an elevation at which each system should be routed. 
  4. Identify systems that we are not modeling, such as fire protection and small conduit racks.  If these systems are not accounted for, problems can arise during construction.

Think about how much easier coordination on the construction side would be if space is provided for the systems mentioned above.  If this step is skipped, a fully coordinated model suddenly becomes uncoordinated or worse, not constructible.  

After going through the process above, each CRB Project BIM Lead will then layout the “No Fly Zones.”  Designers will know where to route their systems, and if a new designer comes onto a project, they have some guidance in the model.

Ultimately, spatial allocation will reduce constructability issues in the field and protect the overall design intent of the model. 

For more information on BIM/ Virtual Design & Construction – see Matt’s previous blog, “A Practical Approach to BIM/VDC – Workflow.”


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Matt Edwards

Matt Edwards

Matt Edwards is a BIM Specialist at CRB in our Raleigh, North Carolina office.
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3 comments

  • March 3, 2016 3:49 pm by Matt Edwards

    Hey Cory, thanks for your question! We use a generic model family that is just a block that can be stretched in all directions. The family contains a type for each discipline that is color coded and semi-transparent. Hope this helps and let me know if you have any additional questions.

  • March 3, 2016 9:27 am by Corey Kavlock

    Couldn't agree more with the importance of communicating plenum space allocation in the begin of the project. What modeled family do use to communicate this to your design team?

  • February 2, 2016 12:46 pm by Alexis Wittman

    Great post.

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