Chapter 4 of 6

Updating & Monitoring

In the GATE Civil syllabus under Construction Management · 2 parts

Cost Control & Earned Value Management · Scheduling & Monitoring — Bar Charts and Milestone Charts

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📑 Contents (15 sections)

Part 1 of 2

Cost Control & Earned Value Management

Last reviewed 16 Sept 2026 · 5 min read

Cost control

Cost control ensures that the project is completed within the approved budget by comparing actual costs with planned costs and taking corrective action.

Steps

Prepare a budget (cost baseline) from the estimate, broken down by WBS/cost codes and time.
Record actual costs (labour, materials, equipment, subcontracts, overheads) against cost codes.
Measure work done (progress).
Compare planned, earned and actual costs; compute variances.
Forecast final cost; analyse causes and take corrective actions.
Report to management; update the plan.

Common causes of cost overrun

Inaccurate estimates and incomplete design; scope changes (variations).
Delays — approvals, land acquisition, utility shifting, slow payments, disputes.
Price escalation of materials and wages.
Low productivity, rework and poor quality; equipment breakdown.
Poor site management and wastage; unforeseen ground conditions.

Earned value management (EVM)

EVM integrates scope, schedule and cost to measure performance objectively.

Basic quantities

Term	Also called	Meaning
Planned value (PV)	BCWS — budgeted cost of work scheduled	Budgeted cost of work planned to be completed by the status date
Earned value (EV)	BCWP — budgeted cost of work performed	Budgeted cost of work actually completed by the status date
Actual cost (AC)	ACWP — actual cost of work performed	Actual cost incurred for the work completed
Budget at completion (BAC)	—	Total budget of the project

FormulaVariances and indices

Cost variance $C V = E V - A C$ (negative → over budget) Schedule variance $S V = E V - P V$ (negative → behind schedule)

Cost performance index $C P I = \frac{E V}{A C}$ ( $< 1$ → over budget) Schedule performance index $S P I = \frac{E V}{P V}$ ( $< 1$ → behind schedule)

FormulaForecasts

Estimate at completion (typical — current cost performance continues):

E A C = \frac{B A C}{C P I}

Atypical (remaining work at budget rate): $E A C = A C + (B A C - E V)$ Considering both CPI and SPI: $E A C = A C + \frac{B A C - E V}{C P I \times S P I}$

Estimate to complete $E T C = E A C - A C$ Variance at completion $V A C = B A C - E A C$

To-complete performance index (to finish within BAC):

T C P I = \frac{B A C - E V}{B A C - A C}

(Using EAC in the denominator instead: $T C P I = \frac{B A C - E V}{E A C - A C}$ .)

Rough time forecast: estimated duration ≈ planned duration / SPI

Interpretation

CPI	SPI	Status
> 1	> 1	Under budget, ahead of schedule
> 1	< 1	Under budget, behind schedule
< 1	> 1	Over budget, ahead of schedule
< 1	< 1	Over budget, behind schedule

TCPI > 1 — the remaining work must be done more efficiently than planned to meet the budget.
On an S-curve plot, the PV curve is the baseline; if the EV curve is below PV → behind schedule; if AC is above EV → over budget.

Part 2 of 2

Scheduling & Monitoring — Bar Charts and Milestone Charts

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.

Worked ExampleBar chart for a small building (illustrative)

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.

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