Traditionally, all major projects have a Master Schedule. It is usually developed in great detail with much thought by the general contractor's project engineer or scheduler. It is useful in finalizing the overall job plans and proving that the job can meet the owner's deadline requirements. One of the fun discussion questions I love to ask when teaching about Lean Project Scheduling is, "How long is the master schedule still accurate once the project begins?" Answers range from days to hours to minutes to "it never was!" The Master Schedule often ends up in the corner of a job trailer - useless for real Project Scheduling.
Why the "traditional" Master Schedule is not enough
The Master Schedule is a point in time forecast and suffers from the fact that almost all forecasts are wrong. Trying to accurately predict the work schedule months and even years into the future is very difficult. The longer the forecast timeframe, the less chance it has of modeling reality. The more detailed one tries to make the plan the greater the chance it will be wrong. On the other hand, the closer to doing the actual work, the more accurate a plan can be. Since projects are a team effort involving many trades, it is very difficult for one person, no matter how experienced, to accurately define each trade's tasks and time requirements.
Lean Project Scheduling (PS)
The purpose of the PS is to empower the workforce to work together as a team, through frequent 2-way project communication, and by allowing the team to take ownership and responsibility for their work as well as the project's milestones and goals.
PS contains five components:
1) Master Schedule - identifies overall activities, sets milestones, and develops Phase Plans to accomplish those milestones
2) Six-Week Schedule - a look into the future so bottle-necks, limiting factors, and roadblocks can be identified in advance
3) Weekly Schedule - a plan of what will be done (includes "Daily Huddle")
4) Weekly Scorecard - what we committed to vs. accomplishments (includes PS meeting)
5) Continuous Improvement Review - what can we do better in the entire process?
PS Master Schedule - a More Complete and Collaborative Alternative
The Master Schedule is useful in providing a big picture of the schedule for the owner. The second part of the Master Schedule is called a "Phase Plan." This is a more detailed and accurate plan that is required for execution. It is developed in a collaborative meeting. By engaging those who will construct the facility in a "phase" soon to be done, the forecast can be more accurate and detailed. During this phase planning session the team will also identify and remove constraints they see as barriers in doing the work. Finally, since developing the phase plan is a team effort, commitments are made and ownership is taken, that is not realized when one person formulates a Master Schedule.
A phase plan should be prepared close to the start of that phase, but early enough to make work ready and assure coordination. Typically, phase plans are prepared at least six weeks prior to the start of the first activity and even sooner if longer lead times have been identified. The ideal way to do phase planning is for the general contractor to lead the session and involve all trades responsible for the work in the specific phase.
Done in Reverse
Phase schedules are best developed using 'reverse planning.' This is done by the team reviewing the Master Schedule and appropriate milestones and defining the work in tasks and sequence. Then the team starts with the last task in the phase to be completed and works back to identify the work needed to complete it. Next, they identify all tasks that must be completed to do the next-to-the-last task, and continuing backward to the beginning of the phase. This back-to-front process identifies the conditions required for work to be released from one activity or task to the next and the coordination necessary to allow multiple activities to proceed concurrently.
This process is best done on a blank wall. Participants add sticky notes for each activity and move these around as new work or other trades add tasks and new relationships are revealed. Each trade or craft writes a brief description of the work/tasks they must perform to complete this phase - one task per sticky note. Each trade will use a different color of sticky pads. They identify what they will "give," meaning the task they do that will release work to the next task (done either by them or another trade). On the same sticky they also identify the task they need to "get," that must be completed by others to release the work to them. The sticky notes (tasks) also contain a time estimate (duration) to perform that work. These tasks represent the "should do" tasks for the project during each phase.
A rough time scale is established so people have a sense of the timing of all the tasks. This is a very participative process with much negotiating. Activities in a phase schedule are highly dependent on each other. They involve routine and repetitive interfaces between trades and therefore require close coordination. The phase schedule identifies the rules for release of work from one activity to the next. An experienced neutral facilitator can help the process go smoothly.
Durations should be established for each task/activity. The durations themselves should represent the most likely time to do the task given the circumstances on the project and the knowledgeable trade partner's estimate of their ability to be reliable. Durations should not include float or contingency time typically added by foremen in reporting the time to perform. The total time to do the phase is the sum of the critical durations of these tasks. The durations will establish the critical path through the phase and, in most cases, float within the phase will become apparent. The team should allocate float time to the most uncertain activities in order to assure that the proper timing of activities remains stable.
If the project is pressed for speed and shortening the schedule is desired, the team should explore how the phase can be accelerated. It should look at what actions will be required, and how the group will respond to early completions. By contrast, if the work in a phase exceeds the available duration, the team must carefully consider alternatives and their costs and open negotiations at the project level in order to best achieve project objectives.
A typical phase scheduling session will take a few hours although the time can be shortened if the team is experienced and/or templates from similar work are available.
A project may have as few as three to as many as 10 to 15 phases depending on the scope and size of the job.
Some phase plan session tips are:
1. Learn in action. Phase planning is not typically done in construction and will feel uncomfortable at first, especially developing the schedule as a multi-trade team. Like learning to ride a bicycle, it takes "doing" to gain confidence.
2. Make sure you have the right people in the session. All trades involved in work during that phase should participate.
3. Prepare people for the session by training them in "why" and "how" the process works and what they need to bring to the meeting. Basic Lean training on the concepts of value, waste and flow is helpful.
4. Have the project drawings available so questions can be answered quickly
5. Do small phases, especially at first, to gain confidence.
6. Work from the end (last task) back - plan from the future.
7. Clarify hand-off criteria (rules of release) and interactions.
8. Encourage debate and discussion.
9. Work to make the phase doable within the milestone. This may require a change in the hand-off criteria.
10. At the end of the session, identify the next phase and when it will be planned.
If only one or more subcontractors are applying the Lean Project scheduling method without the G/C leading and/or other trades participating, the pulling planning process' effectiveness is limited. But it can still help the trade or trades involved to have a better understanding of their part of each phase and the critical hand-off requirements. It is still worth doing.
In summary, the traditional Master Schedule is limited in its usefulness. It should be done to show the major milestones, but not in great detail. A PS Phase Plan should be included as part of the Master Schedule. It includes activities planned in a team effort coordinating the handoffs to make the workflow. Reliability, much needed in doing construction projects, is achieved by collaborative planning and fulfilling promises made by those who will do the work.