Network Diagram From Activity Table

What this diagram shows

This diagram visualises project tasks as nodes connected by dependency arrows, derived from an activity table listing each task's duration, predecessors, and successors. It displays the logical sequence of work, showing which tasks must complete before others begin, and highlights the critical path - the longest sequence of dependent activities that determines minimum project completion time. Time estimates appear on nodes or edges, allowing visual identification of scheduling constraints and slack time in non-critical tasks.

Key components

• Activity node — Represents a single project task with its identifier, name, and duration in days or weeks.
• Dependency arrow — Shows the sequential relationship between tasks, indicating that the destination task cannot start until the source task completes.
• Critical path highlight — Emphasises the longest chain of dependent activities by using contrasting colour or line style, showing which tasks have zero slack.
• Start node — Marks the project's beginning point, typically with zero duration and no predecessors.
• End node — Marks the project's completion point where all critical and non-critical paths converge.
• Activity table — Source data listing each task, its duration, immediate predecessors, and immediate successors for reference during diagram construction.

When to use it

Use this diagram when managing projects with multiple interdependent tasks and you need to communicate scheduling logic, identify scheduling bottlenecks, and calculate project duration. It is essential for PERT and CPM scheduling, resource planning, and explaining why certain tasks are time-critical. Suitable for construction, software development, product launches, and any work with clear task sequences where delay propagation matters.

Common mistakes

• Omitting tasks or including all subtasks without appropriate aggregation, making the diagram unreadable rather than showing dependencies at the correct granularity level.
• Failing to identify or highlight the critical path, so the diagram shows dependencies but obscures which delays actually threaten project completion.
• Adding time values only to nodes without clarity on whether they represent task duration or start/end times, causing confusion about schedule calculations.

Adapting it to your system

Extract task names, durations, and predecessor/successor relationships from your project schedule or work breakdown structure. Create one node per task with its duration prominently displayed. Draw arrows from each task to its immediate successors only, avoiding redundant transitive edges. Calculate earliest start and finish times using forward pass, then latest times using backward pass. Identify tasks where slack equals zero and highlight them as the critical path. Adjust node layout horizontally by time phase to reinforce the schedule visually.