Out-of-logic work means starting tasks in the same location in a sequence which breaks planned logic links. For example, if the plan had overhead MEP before installing studs, any studwork before overhead MEP would be out-of-logic work. Out-of-sequence work is starting locations of the same task in different sequence than planned. For example instead of starting on the 1st floor as planned, studwork starts on the second floor. Both of these are dangerous and can lead to chaos on a project. The main problem is the unpredictability – where will the subcontractors go next? Instead of work following the plan, the plan needs to keep up with the work.
Out-of-logic work rarely happens in the structural phase of the project. However, it is very common in interior work where dependencies are mainly “soft" and work can happen in many alternative sequences. Superintendents and subcontractors are actively looking for opportunities to start work. The logic in the schedule may be irrelevant to them or they may not understand the benefit of following a planned sequence. This causes difficulty with forecasts because they follow planned logic. If the logic change makes sense, there is no problem because it can be easily updated to detail tasks of the schedule. However, it is very common that random out-of-logic work happens on projects which basically invalidates any schedule optimization and in many cases causes productivity loss.
Out-of-logic work can be fixed easily by involving the subcontractors in pull planning meetings and committing to the collaboratively planned sequence (figure 1 shows a picture of a pull planning meeting). Any out-of-logic work should be immediately discussed. If there is a valid reason, the plan should be updated. Otherwise out-of-logic work should be stopped before the project gets out of control.
Best Practice: Utilize pull planning sessions with Subs. What we have found is that GCs know the trades they self-perform and have copious amounts of data that can be harnessed and re-purposed. However, when it comes to subcontractor data, they are woefully lacking, simply because they have not asked. But part of the benefit of our approach is the very collaborative nature of working in concert with subs in pull planning sessions. By asking the subs for crew productivity rates, we can derive a schedule and optimize it to eliminate the stops and starts which hamper and frustrate subs' progress. This simple change can have a tremendous impact: subs are able to work more efficiently without the hassle of de- and re-mobilization.
Out-of-sequence work means that crews are flowing through the building in a different sequence than planned. It happens often because of open RFIs or design issues in a location or because deliveries have been done in wrong sequence. Sometimes out-of-sequence work happens because of subcontractor preferences – get the easy locations first to improve cash flow. The problem is that other succeeding contractors need to follow the same sequence and they may not know it in advance.
Delays can often result because a subcontractor ordered materials and prefabricated based on the planned sequence and the predecessor implemented an unplanned sequence change. If out-of-sequence work happens a lot, total chaos will result. The plan loses all value and it is impossible to predict what will happen next. Out-of-sequence work should only be allowed if there is a valid reason (inability to work in the planned location). In those cases it makes sense to resequence the plan completely. If there is no valid reason, subcontractors should be forced to follow sequence. Again pull scheduling meetings help because subcontractors agree to the sequence together.
To control sequence and logic everyone should commit to the plan, understand tasks and their dependencies and understand what the location-breakdown structure is. Visual Management tools such as production control wall (figure 2) will make this information easily accessible and improve the results on your project.
Best Practice: Create one area in the trailer (we call it a Production Wall) where all crews can see their tasks and locations. This way, there is never a question of who should be where, doing what, when, and why.
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