A construction schedule is the representation over time of all the activities needed to deliver a project. The most common way to draw it is the Gantt chart: one horizontal bar per activity over a calendar.

A good schedule lets you set the duration with sound criteria, coordinate subcontractors, plan purchases and spot delays in time. In this guide we explain how to build one step by step.

If you want to understand why planning matters so much, read why planning is important in a construction project.

Step 1: Break the project down into activities

Start from the budget structure (sections and line items) and group it into plannable activities. Example for a single-family house:

  1. Site setup and layout
  2. Earthworks
  3. Foundations
  4. Ground-floor structure
  5. First-floor structure and roof
  6. Facade enclosures
  7. Roof and waterproofing
  8. Interior partitions
  9. Services (first fix)
  10. Exterior windows and doors
  11. Wall finishes and flooring
  12. Services (second fix)
  13. Painting and finishes
  14. External works
  15. Cleaning and handover

Tip: not so few activities that the schedule says nothing, nor so many that nobody can maintain it. For a mid-size project, between 50 and 200 activities is usually reasonable.

Step 2: Calculate durations from productivity rates

Don't estimate by eye. Duration is calculated from the quantity and the crew's output:

Duration = quantity / (output rate × number of crews)

Example: 450 m² of brick masonry. One crew (skilled worker + laborer) builds about 18 m² per 8-hour day.

  • With 1 crew: 450 / 18 = 25 days.
  • With 2 crews: 450 / 36 = 12.5 days → 13 days.

Productivity rates come from the same unit price analysis you used in the budget, so schedule and cost stay aligned.

Step 3: Define dependencies

Dependencies set the logical order between activities. There are four types:

  • Finish-to-Start (FS): B starts when A finishes. The most common (the structure starts when the foundations finish).
  • Start-to-Start (SS): B starts when A starts, often with a lag (wall finishes start 5 days after partitions start).
  • Finish-to-Finish (FF): B finishes when A finishes.
  • Start-to-Finish (SF): rarely used.

Lags (positive or negative) let you overlap activities realistically, for example respecting concrete curing time before stripping the formwork.

Step 4: Identify the critical path

The critical path is the sequence of activities that determines the total duration of the project. Any delay in a critical activity delays the end of the project.

  • Critical activities have zero float.
  • Non-critical activities have float: they can slip by that amount without affecting the end date.

Knowing the critical path tells you where to concentrate resources and attention.

Step 5: Add milestones

Milestones are key events with no duration: signing the site layout record, end of structure, building weathertight, delivery of critical supplies, completion. They are used to report progress to management and the client, and are often tied to payments or penalties.

Step 6: Assign resources and check the load

Assign each activity its resources (crews, subcontractors, crane). Check that there are no impossible peaks: for example, three activities that need the crane at the same time. If there are, level the schedule by shifting activities that have float.

Step 7: Work calendar

Set up the calendar with local holidays, vacations, working hours and, where relevant, low-productivity periods (rain, extreme heat). A schedule without a realistic calendar tends to be optimistic.

Step 8: Save the baseline and track progress

Once the schedule is approved, save it as the baseline. From then on:

  • Update the actual progress of each activity weekly.
  • Compare with the baseline to see delays.
  • Recalculate the critical path.
  • Make decisions: more resources, sequence changes, overlaps.

We explain it in detail in how to monitor a construction project.

From Gantt to cost: the S-curve

If each activity is linked to budget line items, the schedule produces the S-curve: cumulative planned production month by month. It is the basis for:

  • Forecasting billing and cash flow.
  • Calculating the planned value (PV) of earned value management. See construction cost control.
  • Planning purchases and subcontractor hiring.

This link between time and cost is the essence of 5D BIM.

Tools for building a construction schedule

  • Microsoft Project: widely used on mid-size projects.
  • Oracle Primavera P6: widespread on large projects.
  • ProjectLibre and GanttProject: free, open alternatives.
  • Excel: possible for simple schedules, but without critical path calculation.
  • Odoo Project: Gantt view for planning tasks (available in Odoo Enterprise).
  • BIM 2.0 for Odoo: integrates with Microsoft Project to link planning with the budget, progress and certifications.

Common mistakes

  • Durations estimated without productivity rates.
  • Forgetting lead times for long-lead materials (windows and doors, elevators, transformers).
  • Not including technical times (curing, testing, permits and approvals).
  • Not updating the schedule once work has started.
  • A schedule disconnected from the budget and from cost.

Frequently asked questions

What is the difference between a schedule and a Gantt chart?

The schedule is the time plan of the project; the Gantt chart is the most common graphical way to represent it.

What is the critical path of a project?

The chain of activities with no float that determines the total duration. If one slips, the project slips.

Can I build a construction Gantt chart for free?

Yes, with ProjectLibre or GanttProject. There are more options in free construction estimating software.

Conclusion

A useful construction schedule is built from well-defined activities, durations based on productivity rates, logical dependencies and a clear critical path. And it becomes truly powerful when it is connected to the budget and to cost tracking.

👉 Find out how BIM 2.0 connects Microsoft Project with your projects: request a demo.