Gantt Charts Are the Most Widely Used Project Schedule Format
While CPM networks provide the analytical backbone of construction scheduling, Gantt charts are the most commonly used format for communicating project schedules to clients, owners, and project teams. Most architects will work with Gantt charts far more frequently than precedence network diagrams - and the ARE PjM exam expects candidates to be fluent in reading and interpreting them. Understanding what a Gantt chart shows, what it cannot show, and when to use it versus CPM is an important practical skill.
What a Gantt Chart Is
A Gantt chart (named for Henry Gantt, who popularized it in the early 20th century) is a horizontal bar chart that displays project activities on the vertical axis and time on the horizontal axis. Each activity is represented by a horizontal bar whose length corresponds to the activity's planned duration. The chart provides an immediate visual representation of when activities start, how long they take, and which activities overlap.
What a Gantt Chart Shows
- Activity names and their planned sequence
- Start and end dates for each activity
- Duration of each activity (bar length)
- Which activities are planned to run concurrently
- Milestones (typically shown as diamonds or vertical lines)
- Percent complete (when used for progress tracking)
What a Gantt Chart Does NOT Show
This is where candidates trip up. A Gantt chart does not explicitly show dependencies between activities (which activity must finish before another can start) or float (schedule slack). Dependencies are often implied by the visual sequence but are not formally represented. Because of this limitation, Gantt charts cannot directly identify the critical path - that requires a CPM analysis that is then imported into the Gantt format. Modern scheduling software like Primavera P6 or Microsoft Project performs CPM analysis and displays results in Gantt format, giving the best of both worlds.
Gantt Chart for Architectural Services
Architects use Gantt charts to schedule design phases and deliverable milestones for clients. A typical architectural project Gantt chart might show: Programming (4 weeks), Schematic Design (6 weeks), SD review (2 weeks), Design Development (8 weeks), DD review (2 weeks), Construction Documents (12 weeks), Bid period (4 weeks), and Construction Administration (52 weeks). Milestones mark owner review submissions, permit applications, and bid dates.
Comparing Gantt and CPM
| Characteristic | Gantt Chart | CPM Network |
|---|---|---|
| Visual clarity | High - easy to communicate | Low - complex to read |
| Shows dependencies | Implied only | Explicitly modeled |
| Shows float | No | Yes |
| Identifies critical path | No | Yes |
| Best for | Client communication, overview | Schedule analysis, delay claims |
Key Exam Points
- Gantt charts show duration and sequence but not dependencies or float.
- Gantt charts cannot identify the critical path - that requires CPM analysis.
- Milestones on Gantt charts mark key decision points and deliverables.
- Most modern scheduling software combines CPM analysis with Gantt display.
- Architects use Gantt charts to schedule design phases and communicate with clients.
Study PjM on AREprep
AREprep’s PjM flashcards cover every concept on this exam with spaced repetition, and the practice exams mirror the real question formats so the actual test feels familiar.