Last reviewed 16 Sept 2026 · 5 min read
Scheduling
Scheduling is fixing the start and finish times of each activity on a calendar, respecting logic, durations and resource limits.
Purposes
- Know when each activity will be done; determine the completion date.
- Plan procurement of materials, labour and equipment.
- Coordinate subcontractors and agencies.
- Provide a baseline for monitoring progress and cash flow.
Bar chart (Gantt chart)
Developed by Henry L. Gantt (early 20th century). Activities are listed vertically and each is shown as a horizontal bar along a time scale; bar length represents duration.
Construction of a bar chart
- List the activities (from the WBS).
- Estimate durations.
- Decide the sequence and start dates.
- Draw bars against the time scale; show actual progress by a second bar or shading.
| Activity | Duration (weeks) | Start week | Finish week |
|---|---|---|---|
| Site clearance and setting out | 1 | 1 | 1 |
| Excavation | 2 | 2 | 3 |
| Foundation concrete and plinth | 3 | 4 | 6 |
| Superstructure (RCC frame, masonry) | 8 | 7 | 14 |
| Plumbing and electrical rough-in | 4 | 11 | 14 |
| Plastering | 3 | 15 | 17 |
| Flooring | 2 | 17 | 18 |
| Painting and finishing | 2 | 19 | 20 |
Overall duration: 20 weeks. Plumbing overlaps superstructure (weeks 11–14) — parallel activities are easily visualised.
Advantages
- Simple to prepare and understand — even by non-technical people.
- Clear visual picture of time-scale and overlapping activities.
- Useful for small projects and for presenting summaries.
- Can show planned vs actual progress and resource loading.
Limitations
- Interdependencies between activities are not shown — the effect of delay in one activity on others cannot be seen.
- Does not identify critical activities or floats.
- Uncertainty in durations cannot be represented.
- Difficult to update and to use for large, complex projects with many activities.
- Progress in terms of physical percentage is judged subjectively.
- No time–cost trade-off analysis.
These limitations led to milestone charts and later network techniques (CPM, PERT).
Linked bar chart
A bar chart with arrows linking dependent activities — shows logic partially; modern software displays Gantt charts linked to network logic.
Milestone chart
A milestone is a significant event (point in time, zero duration) — e.g. "foundation completed", "roof slab cast".
- A milestone chart is an improvement over a bar chart in which milestones are marked on bars, dividing long activities into sub-activities with key events.
- Helps monitoring long activities and showing some sequence within an activity.
- Still does not show interdependencies between milestones of different activities — which led to network diagrams (milestones connected by arrows became the forerunner of PERT networks).
Monitoring progress on bar charts
- Planned bar vs actual bar drawn beneath or shaded.
- A status (time-now) line drawn at the reporting date; activities behind the line are behind schedule, ahead are ahead of schedule.
- Percentage completion marked on bars.
Line of balance (LOB)
A technique for repetitive projects — multi-storey buildings (floor by floor), housing units, pipelines, highways.
- Plots cumulative units completed (vertical axis) against time (horizontal axis) for each activity/crew — each crew's progress is a line whose slope = production rate.
- Parallel lines indicate balanced crews moving continuously from unit to unit; converging lines indicate conflicts (crews catching up).
- Helps maintain continuity of work and identify bottlenecks.