Creating Hammock Tasks in MS Project
August 30th, 2009 | 
Author: A hammock task can be defined as either a summary task that aggregates a related set of activities, or an actual ongoing activity whose start and finish is driven by other tasks or milestones that may or may not be related. In the first case, summary tasks are easily created using the outline feature in Project of course but the second case can present more of a challenge.
In the simple example below, two non-summary hammock tasks are shown.
Both hammocks reflect ongoing activity from the start to the finish of the project. To create Hammock A:
- Click in the Start cell for the project “Start” milestone and choose the Copy command
- Click the Start cell for “Hammock A” and choose Edit, Paste Special, Paste Link, and click OK
- Click in the Finish cell for the project “Finish” milestone and choose Copy
- Click in the Finish cell for “Hammock A” and paste as a link again
A problem with hammocks is that they may show up as critical items (as here with Hammock A) whereas in reality they do not actually drive the project schedule. Hammock B shows how we can avoid this by linking the finish date to a ‘dummy’ milestone “Finish -1″ that we set to finish just before the project finish (predecessor is Finish milestone SF-1).
Using either approach above will allow the hammock to ‘stretch’ or ‘shrink’ as the durations of the other tasks change, during plan updates for example. If necessary, a manual click on the F9 key will force a correct recalculation of the hammock’s duration.
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This has been helpful. However, I have followed these instructions, but the duration is still driving the length of the hammock tasks, so I’m having to change the duration for them to still have the same linked start and linked finish dates. (I’ve marked ‘estimated’ for duration but that doesn’t help). What am I doing wrong? (I’m creating a starting point schedule for several PMs to use for similar projects.) Also, when it asked if links should be updated when the file is open, it seems that I should always say ‘no’. Is that correct? I am using Project 2010, but am also saving as Project 2003, if that makes a difference. Thanks!
Hi JB,
Thanks for your mail. If the duration of the hammock tasks is not being driven by the sub-tasks, please check that the hammock tasks are not set to Fixed Duration otherwise their own duration will always remain unchanged – they’ll need to be set to Fixed Units or Fixed Work. This can be done by double-clicking on the Hammock task name, then click the tab “Advanced”, and then select the “Task type” from the dropdown.