A Primavera P6 schedule is often required at the start of a project, regardless of whether it is simple or complex, to forecast the duration of the project and its activities. A schedule should be made prior to the start of a project. It should be a robust plan that lays out what needs to be done, by whom and when, while assessing any risks to the project. This is all done with the goal of delivering the projects deliverables to the quality standards while finishing on time and on budget.
Prior to starting a Primavera P6 schedule you must first create a Work Breakdown Structure (WBS). Note that some scheduling tools don’t insist that this is done despite it being considered best practice. A WBS should be thought of as the key deliverables of the project.
The WBS contains all activities needed to complete the project. However, it does not specify how or when the activities will be done, as the WBS is not a schedule.
Creating a Primavera P6 Schedule
A Primavera P6 schedule typically includes the following steps:
- Planning stage – where a project statement is made describing the project, highlighting all phases. Sub sections could include legal requirements, Quality Assurance etc.
- The WBS lists the deliverables of the project.
- Create Project Calendars for activities and resources. These can include the standard 5-day workweek, shift patterns, etc.
- Create activities for the project, breaking them down into manageable pieces of work and assign resources.
- Milestones – Activities spell out the steps to meet a Milestone. Milestones have a fixed date but no duration and are a specific point in time during the project lifecycle. They are used to measure progress towards completion. They may be included for budget checks or as a reference point, which marks a major event or decision point within the project.
- Relationships are links between activities which create the sequence and network logic for the project e.g. Activity B cannot start before Activity A has finished.
- Assign Resources – Human resources such as a particular skill set, equipment, facilities, other costs can be assigned to individual activities.
- Risk – Capture the potential risks and dependencies, which could affect the delivery of a milestone or deliverable.
- Schedule baseline – A schedule baseline is approved by the project stakeholders and incorporates the cost baseline (which is the approved budget) prior to the start of the project.
- Execution – Moving to the execution phase requires monitoring and controlling of the project schedule. Regular updates from the work performed together with remaining effort required are essential. Additional work scope or change orders will need to be considered and may affect the schedule.
A Primavera P6 schedule’s primary purpose is to manage the amount of time, effort and cost it takes to complete a project scope of work to its defined quality standards.
Critical Path Method (CPM)
The technique for using CPM is to construct a model of the project which includes the following:
- A list of all the activities required to complete the project derived from the WBS.
- Assign the time (duration) that each activity will take to complete. In order to assign the duration for each activity, so that it is as accurate as possible, the scheduler may follow three processes:
- Draw on their own knowledge of an activity.
- Consult other project teams to find the duration of an activity.
- Review references to ascertain the duration. For example if you were baffled by the duration of an activity you could reference it on line or via Project Management books/articles.
- Draw dependencies between each activity. Dependencies are the relationships between the activities needed to complete the project in a logical order. There are four types of relationships:-
- Finish to Start is the most common relationship used. The Predecessor task (the previous or first task) must finish before the Successor (next) task starts. For example the foundations have to be completed before building the structure starts.
- Start To Start. The Predecessor task must start before the Successor can start. For example the bricks and materials have to be on site before brick building can start.
- Finish to Finish. The Predecessor task must finish before the Successor can finish. For example a major building complex would have to finish before the road infrastructure could be completed.
- Start to Finish. The Predecessor task must Start before the Successor can finish. For example you cannot invoice a product without producing it or delivering it.
Once all the activities have relationship ties, the Critical Path can be calculated. A project schedule is a list of activities with estimated durations that are logically linked together, in order to forecast the Total Project Duration.
Based on this criteria, the CPM is calculated through the Primavera P6 software. CPM uses a mathematical algorithm to calculate a Critical Path based on the activities, their durations and their inter relationships. The Critical Path displayed on the Gantt Chart is the Longest and Shortest possible path through your network of activities. Any delay (or acceleration) to an activity on the Critical Path will have an effect on the overall Project Finish Date.
Total float is the amount of time (hours, days or weeks) that an activity can be delayed before it joins the Critical Path and affects the Project Finish Date.
Scheduling fundamentals revolve around breaking down your project into digestible sized deliverables and activities. It involves taking those activities and estimating their duration based upon your personal knowledge, group estimating websites or knowledge of experts.
Tying these activities together with relationships and letting the schedule engine do its thing, then tells you the total project duration. Scheduling is an important tool in project management as it allows a realistic time scale of the project duration. Also, as the project progresses, it’s easy to reschedule and see the impact of any changes. It optimizes labor and materials and the sequence of activities are integrated with the budget.
A Primavera P6 schedule allows the project team to gain early insight into any risks to the project duration, which may prevent it from finishing on time and within budget.