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BUS-CONS57-02 · Lesson 4 · 14 clock hours · demo

Gantt Charts and Scheduling Software Basics

Objective. Students will enter a project activity list with logic links into scheduling software and produce a formatted Gantt chart that displays the critical path and float.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a credentialed professional in the field or by a certification or approval body. It is a study draft and may contain errors. Do not use it as instructions for work on a job site or on live equipment. Always follow your instructor, your supervising professional, and current official references and regulations.

VoTechWorks program approval and accreditation are still in progress. Credentials are issued only by the certifying bodies named in each program, after their own exams.

What a Gantt Chart Does

A Gantt chart is a horizontal bar chart that maps every project activity against a calendar. Each bar starts at the activity's early start date and ends at its early finish date. Project owners, subcontractors, and inspectors all read Gantt charts, so the ability to build one quickly and accurately in scheduling software is a core skill for any construction manager or estimator.

Software such as MS Project and Primavera P6 calculates dates automatically once you enter two things: the duration of each activity and the logic links between activities. The software then runs a forward pass and backward pass — the same math you did by hand in Lesson 3 — and color-codes or flags the critical path for you.

Key Elements of a Professional Gantt Chart

A chart submitted to an owner or included in a project manual must contain several standard elements.

Title block. Place the project name, contract number, company name, preparer's name, and the date the schedule was printed in a title block. Many owners require this as a contract deliverable.

Timescale. Select a timescale that fits the project. For a tenant improvement of several weeks, a weekly timescale is usually appropriate. Monthly timescales suit multi-year projects. The timescale must be labeled clearly so a reader can identify any date without asking questions.

Critical path highlighting. Critical path activities — those with zero total float — should be visually distinct. In MS Project, you can apply the critical path filter or format critical task bars to display in red. In Primavera P6, you set the bar style for critical activities to a contrasting color. This is not optional on professional submittals; reviewers look for it immediately.

Milestone diamonds. Milestones mark a single point in time: a permit issuance, an owner review meeting, or a substantial completion date. Software represents milestones as diamonds on the chart. Add all contract milestones so the schedule tells the full story of accountability.

Float display. Some owners require float bars — thin lines extending from the end of an activity bar to its late finish date — to be shown. Even when not required, reviewing float bars helps you spot schedule risk at a glance.

Setting Up the Software File

When you open a new project file, enter the project start date first. Everything the software calculates depends on that anchor. Next, set the project calendar: a standard five-day work week, any holidays the contract recognizes, and any owner-mandated shutdown periods. Errors in the calendar are a leading cause of Gantt charts that look correct on screen but deliver wrong dates to the field.

Enter each activity with a unique ID, a clear description, and a duration in working days. Avoid vague descriptions such as "Rough-in work" — write "Electrical rough-in, Floor 2" instead. When activities are named precisely, subcontractors can find their own work on the chart without guidance.

Entering Logic Links

Logic links in software mirror the Precedence Diagramming Method (PDM) network you built by hand. The most common relationship is Finish-to-Start (FS): the successor cannot start until the predecessor finishes. You can also assign lags (positive delays) or leads (negative values that allow overlap) to any link.

After you enter all links, run the scheduler. Compare the software-calculated early start, early finish, and total float values for every activity against your hand-calculated PDM network from Lesson 3. If any activity shows a different date, trace the logic: a missing link, a wrong duration, or a calendar error is usually the cause. Never accept a discrepancy and move on — an incorrect critical path submitted to an owner can result in costly claims or schedule disputes.

Formatting and Exporting

Formatting is not cosmetic. A poorly formatted schedule communicates unprofessionalism and can cause a submittal to be rejected. Follow these steps before exporting:

1. Apply the critical path bar style (red or bold, depending on company standard).

2. Insert milestone diamonds for every owner review date in the contract.

3. Set the timescale to weeks for a tenant improvement project.

4. Insert or confirm the title block in the header or footer.

5. Fit the chart to a standard paper size (typically 11 × 17 or D-size) so bars are readable.

6. Export to PDF — never submit a native project file as a deliverable unless the contract requires it, because the recipient may not have the same software version.

Save the native file as well and keep it in the project folder. You will update the schedule throughout construction as work progresses.

Safety in the Computer Lab

This lesson takes place entirely at computer workstations. While the hazard level is low compared to field work, a few points apply. Keep power cords and laptop cables secured and out of walkways to prevent trip hazards — this is a basic housekeeping requirement on any job site and in any office. Do not block emergency exits with chairs or equipment. If a workstation shows signs of electrical malfunction (burning smell, sparking), stop work immediately, do not attempt to repair it yourself, and report it to the instructor. These habits reflect the same safety culture that OSHA 30 training reinforces: recognize the hazard, stop the exposure, report it.

Connecting to Your Credentials

NCCER Project Management covers schedule development and control as a core competency. CMAA's CMIT exam tests your ability to interpret and produce construction schedules. OSHA 30 reinforces the connection between the schedule and safety planning — phasing of work affects when and where hazards appear on site. A Gantt chart is not just a management tool; it is also a safety planning document that shows when excavations, crane picks, and confined-space entries will overlap.

Key terms8

Gantt chartA horizontal bar chart that displays project activities as bars plotted against a calendar, showing planned start and finish dates for each activity.
Critical pathThe longest continuous sequence of activities in a project network; any delay to a critical path activity delays the project finish date.
Total floatThe amount of time an activity can be delayed from its early start without delaying the project's calculated finish date; critical path activities have zero total float.
MilestoneA scheduled event with zero duration that marks a significant point in the project, such as owner approval or substantial completion; displayed as a diamond on a Gantt chart.
Finish-to-Start (FS) relationshipA logic link in which a successor activity cannot begin until its predecessor activity is complete; the most common relationship in construction scheduling.
LagA positive time delay added to a logic link, requiring a waiting period between the end of one activity and the start of the next.
Project calendarThe scheduling software setting that defines working days, shift hours, and non-working days such as weekends and holidays; it controls how the software converts durations into calendar dates.
Forward and backward passThe two-step mathematical process used to calculate early dates (forward pass) and late dates (backward pass) for every activity in a project network.

Worked examples4

1. You enter five activities into MS Project with the following durations and Finish-to-Start links: A=3 days, B=5 days (follows A), C=4 days (follows A), D=2 days (follows B and C), E=3 days (follows D). The project starts on Day 1. What is the critical path and total project duration?
  1. Forward pass — Path A→B→D→E: Early finish of A = Day 3. Early start of B = Day 4, early finish = Day 8. Early start of D = Day 9 (driven by B, since B finishes Day 8 and C finishes Day 7). Early finish of D = Day 10. Early start of E = Day 11, early finish = Day 13.
  2. Forward pass — Path A→C→D→E: Early finish of A = Day 3. Early start of C = Day 4, early finish = Day 7. D is already constrained to start Day 9 by B, so C does not drive D.
  3. Total project duration = 13 working days, set by path A→B→D→E.
  4. Backward pass — Late finish of E = Day 13, late start = Day 11. Late finish of D = Day 10, late start = Day 9. Late finish of B = Day 8, late start = Day 4. Late finish of A driven by B: late finish = Day 3, late start = Day 1. Late finish of C = Day 8 (must finish before D starts Day 9), late start = Day 5.
  5. Total float: A=0, B=0, D=0, E=0 (critical); C has early finish Day 7, late finish Day 8 — total float = 1 day (non-critical).
  6. Critical path: A → B → D → E.
Answer: Critical path is A→B→D→E with a total duration of 13 working days. Activity C has 1 day of total float and is not on the critical path.
2. After entering the schedule above, your software shows Activity D starting on Day 10 instead of Day 9. What is the most likely cause and how do you fix it?
  1. Check whether the predecessor link from B to D was entered correctly. If B is linked to D with FS+1 lag instead of FS+0, the software adds one extra day, pushing D's early start to Day 9+1=Day 10.
  2. Open the task information or predecessor dialog for Activity D. Review the lag value on the link from B.
  3. Change the lag from 1 to 0 and re-schedule. Verify that D now shows early start = Day 9.
Answer: A lag of 1 day was accidentally applied to the B→D link. Removing the lag (setting it to 0) restores the correct early start of Day 9 for Activity D.
3. You are formatting the Gantt chart for submittal. The project runs 9 weeks. Should you set the timescale to days, weeks, or months? Justify your answer.
  1. A 9-week project displayed at a daily timescale would produce 45 columns of bars, making the chart very wide and individual bars hard to distinguish on a standard page size.
  2. A monthly timescale would show only about 2 months, compressing all 9 weeks into too few columns to read individual activity start and finish dates precisely.
  3. A weekly timescale produces 9 columns — enough resolution to read start and finish dates within a few days, while fitting neatly on an 11×17 or D-size sheet.
Answer: Set the timescale to weeks. It provides enough resolution to read individual activity dates accurately while keeping the chart compact enough to print on a standard large-format sheet.
4. Activity 'Install ceiling grid' has an early start of Day 22, early finish of Day 26, late start of Day 25, and late finish of Day 29. Calculate total float and state whether it is on the critical path.
  1. Total float = Late Start − Early Start = 25 − 22 = 3 days.
  2. Alternatively, Total float = Late Finish − Early Finish = 29 − 26 = 3 days (same result, confirms the arithmetic).
  3. Because total float is greater than zero, the activity is not on the critical path.
Answer: Total float = 3 days. 'Install ceiling grid' is not on the critical path and does not need to be highlighted in red on the Gantt chart.
In class: Instructor demonstrates creating a new project file in MS Project or Primavera P6, entering activities, assigning durations, and linking predecessors; students follow along on individual workstations. · Students enter the 15-activity tenant improvement schedule from Lesson 2 into the software, link all activities per their PDM network from Lesson 3, and verify that the software-calculated critical path matches their hand calculation. · Students format the Gantt chart with a project title block, timescale in weeks, critical path highlighted, and milestone diamonds for owner review dates; they export a PDF for the lab log.
Materials: Computers with MS Project or Primavera P6 (student license or school lab), projector for instructor demo, activity list from Lesson 2, PDM network from Lesson 3
Check: Exported Gantt chart PDF reviewed against a formatting checklist (title block, timescale, critical path color, milestones): pass requires all five checklist items present and critical path matching the hand-calculated answer key.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

NCCER Project Management — Schedule Development
1. In scheduling software, what is the first piece of information you must enter before the software can calculate correct calendar dates for any activity?
CMAA CMIT — Schedule Analysis
2. Which activity characteristic defines whether an activity falls on the critical path?
NCCER Project Management — Schedule Development
3. A student's software shows Activity G starting two days later than the hand-calculated early start. Which of the following is the MOST likely cause?
CMAA CMIT — Schedule Presentation
4. On a professional Gantt chart submittal, how should critical path activities be visually distinguished from non-critical activities?
CMAA CMIT — Schedule Analysis
5. A project activity has an early finish of Day 14 and a late finish of Day 14. What is its total float, and what does that value mean?
NCCER Project Management — Schedule Development
6. Which timescale is MOST appropriate for a tenant improvement project scheduled to last approximately 10 weeks?
CMAA CMIT — Schedule Development
7. What does a milestone diamond on a Gantt chart represent?
OSHA 30 — General Safety and Health Provisions
8. A student notices that a power cord from a lab workstation is running across the main aisle. What is the correct action, consistent with OSHA safety principles?
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