Blog | Why WBS Summary Activities are King!



Why WBS Summary Activities are King!

Given the choice, when a need arises in a project schedule for a summary level activity I always try to utilize WBS Summary activities over LOE”s.  Why is very simple….NO RELATIONSHIPS TO CREATE OR MAINTAIN.  Did you know that when you have an LOE that is Not Started and has an incorrect relationship with an underlying activity the Duration of the LOE, upon scheduling, reverts to zero, therefore, causing all Resource Budgeted Units assigned to the LOE to revert to zero!!  Did you also know that if you have an LOE that is In Progress and has an incorrect relationship with an underlying activity the Duration of the LOE, upon scheduling, reverts to zero, therefore, causing any assigned Resource Remaining Units to revert to zero!!  NOW THEN.. HEAR IT AGAIN….A WBS Summary activity has no relationships to cause this phenomena.

The WBS Summary activity type combines the summary capabilities of the WBS structure with task level attributes, such as, resource assignments, activity codes and notebooks.  It is used to roll up date, durationand percent complete values for a group of activities that share a WBS Code.  The WBS Summary activity can also be used in a detailed schedule to roll up into a Gantt Chart with a nice waterfall look from beginning to end of the project using Start or Finish as your sort (perhaps a level 2 schedule otherwise unattainable through the use of WBS elements or Activity Codes).

  • Start and Finish dates for a WBS Summary activity are set to the Earliest Start Date and Latest Finish Date respectively of all activities within its WBS.
  • The WBS Summary activity Start and Finish Dates are rolling dates that will fluctuate with the Earliest and Latest Dates of the activities within the WBS group that are not started or in-progress
  • Once all activities within the WBS are complete the Start and Finish Dates of the WBS Summary activity will equal the earliest Early Start and latest Early Finish Date of the activities within its WBS group
  • WBS Summary activities provide a great place to assign clerical, security and overhead Resource assignments to the life of the project or a specified segment of the project e.g. construction phase

So, when would I use an LOE activity?  When I need to capture a  summary level segment of the schedule that does not make sense to identify with a WBS element…and that is the only time.

Happy Summarizing and here’s to the end of bad relationships.  Hail to the King!

  1. Hey Marc,

    It’s Cara from West Valley. Just stumbled upon your article. I’m definitely going to utilize these for Executive Management Purposes. Thanks, as always!


  2. Hi Zac,

    Here are two thoughts on how you might approach your EV labor unit roll up. You can try creating an activity code and assign to the activities that you want to see summary hours for and the totals will then show in the Activity Code Grouping Band. Another option would be to use the Assignments View and assign a resource to the activities that you want to summarize units for. As a thought CBA provides support for assisting with P6 solutions. If you would want to contact me directly my email is

  3. Hey Marc,
    Thanks for the quick response and explanation. Do you have any suggestions on how I might accomplish this otherwise?
    Basically I want to take the earned value labor units from several different activites, sum them, and then take that sum and use it in a global change which involves another user defined value (the other value is not a summary value, it is a single, entered value). If not, no big deal, but I figured I would ask! Thanks again!

  4. Hi Zac,
    The WBS Summary activity was not designed to summarize units. Reason being that WBS Summary activities can have resources and therefore units assigned to them. Units are rolled up in the WBS element itself.

  5. Hey I was wondering if you know if there is any way to have the wbs summary activity summarize units? I have three-four activities that all have units and %’s complete and I want to tally them and compare them to a single number – I was thinking I could do this with a wbs summary activity, but I can’t figure out how to tally units data into a single activity. Any ideas?