Specify Constraints For Scheduled Tasks

When building and managing a construction schedule, the planned start and finish dates for tasks and activities are determined in several ways:

• Manual setup – dates are directly entered by the scheduler.
• Automatic setup – dates are derived from predecessor timelines and dependency relationships.

In addition to these methods, the scheduler allows you to apply explicit constraints on the start or finish dates of individual leaf-level tasks in the WBS. Once applied:

• The scheduler auto-adjusts the planned timelines of the constrained task, overriding dependency logic, where required.
• Successor tasks are recalculated automatically based on the new dates.
• Parent-level task timelines are progressively updated.
• Constraints help align the schedule with real-world conditions such as contractual deadlines, external approvals, resource availability, planned milestones, or even weather forecasts.

These constraints are also factored into advanced calculations like critical path analysis and risk forecasting.

You can apply a primary constraint and a secondary constraint to the applicable tasks. Constraints are of different types, each tied to a date specification. See the knowledge base article Task Level Constraints to learn more.

To apply a primary constraint to a task

• Navigate to the schedule page of the project
• Ensure that you are in the grid view
• Double-click inside the '1st Constraint Type' cell of the task row

• Select the constraint type. See Task Level Constraints for descriptions of the constraint types.
• Click inside the next cell under the '1st Constraint Date' column and use the calendar to select the date that applies to the constraint. 

Depending on the type of constraint applied, the planned start or finish dates of a task will adjust by balancing the flexibility of the constraint with the dependency logic of the task. For example:

Flexible constraint – "Start On or After"

• If the dependency-driven planned start date is later than the specified constraint date, the task will not change, since it already meets the condition.
• If the dependency-driven planned start date is earlier, the task’s start will shift forward to align with the constraint date.

Inflexible constraint – "Must Finish On"

• Regardless of dependency-driven dates, the task is forced to end exactly on the specified date.

This may create negative float or out-of-sequence logic if predecessor activities push the task later, since the constraint overrides the network logic completely.

To apply a secondary constraint

• Double-click inside the '2nd Constraint Type' cell of the task row and follow the same procedure as above.

Please note that the secondary constraint option is only available for certain primary constraint types. See the knowledge base article Task Level Constraints to learn more.