In construction project planning, a well-structured Work Breakdown Structure (WBS) lays the foundation for organizing activities and tracking progress. However, the true value of a WBS isn’t just in listing activities; it lies in how those activities are sequenced and connected. Minimizing the total float within the construction WBS by properly linking activities or adding lags together is a strategy to improve schedule practicality.

Linking activities logically and adding lags efficiently reflects actual site dependencies and allows the schedule to highlight critical paths more accurately. When float is minimized, planners gain better visibility into potential delays, and project teams are more proactive in addressing sequencing issues. In this article, we’ll explore how strategic activity linking within your construction activities or adding lags between construction activities can tighten the schedule, reduce ambiguity, and improve project control.

Minimize Total Float Concept

Total Float is the amount of time an activity in a project schedule can be delayed without delaying the project’s overall finish date, assuming the project follows the critical path method (CPM). As mentioned before in our previous articles, minimizing the total float enhances the realism of the schedule submitted.

In past articles, we explained minimizing it in pre-construction activities using several methods. We explained in a previous article how important it is to minimize total float when creating a baseline schedule according to the Defence Contract Management Agency (DCMA) because high float values may indicate missing logic or poorly defined activities.

Here are the links to the articles in case you want to check them:

1. Decrease the Total Float of Preconstruction Activities using As Late As Possible Constraint

2. Primavera P6 Best Practices: How to Manage Shop Drawing Submittals with Activity Linking vs Lag Time

3. The Application of Start-to-Finish [SF] Relationship in Primavera P6

4. How to Review a Submitted Baseline Schedule [Checklist]

Case Study to Minimize Total Float for Construction Activities

As can be seen in the screenshot below, the external works have a total float of 127 days, and it is not logical to assume that the external works will start at the start of the project. Also, masonry activities have high total floats, such as 44 days. So, we need to shift the activities a bit, but how?

We can use two methods, using any of them depends on what the consultant wants or recommends, or if it is mentioned in the contract.

Method one: Linking Activities with each other to Minimize Total Float

Method two: Adding Lags to Minimize Total Float

We will use the first method with the external activities and the second method with the masonry works.

Method One: Linking Activities with each other to Minimize Total Float

It is neither practical nor cost-effective to initiate all construction activities at once at the start of a project. Doing so can place unnecessary financial strain on the contractor during the early phases and fail to represent the actual site conditions. Instead of allowing unrelated activities to begin illogically at the project’s start, a more strategic approach is to establish logical relationships between them. For example, the external backfilling activity can be linked to the completion façade works after removing the scaffolding to start the backfilling meanwhile the internal finishing works is leading the project. This sequencing not only shifts external works later in the timeline by bringing the schedule closer to real-world conditions but also helps minimize total float and enhances the overall accuracy and reliability of the construction program.

Method Two: Adding Lags to Minimize Total Float

To minimize total float and create a more efficient and logical schedule, lags can be introduced to ensure masonry activities commence sequentially across different floors. 

Lag: a planned delay between two linked activities in a project schedule. It represents the amount of time that must pass after one activity starts or finishes before the successor activity can start or finish, depending on the type of relationship used.

This sequencing strategy helps optimize labor resource utilization by enabling a single skilled team to perform all masonry work throughout the project. Since laborers are typically compensated daily, aligning the activities consecutively prevents idle time between floors. This approach not only reduces unproductive paid days but also enhances cost efficiency and supports a smoother construction workflow.

Note that it is important to refer to the contract first to make sure that the use of lags is acceptable. Also, ask the consultant what the number of acceptable lag days is and what the acceptable justifications are.

Some Justifications That Can Be Used and Their Cases

1. Concrete Curing Time

• Justification: After pouring concrete, there is a required curing period before subsequent work can proceed.
• Example: Add a 7-day lag between “Slab Casting” and “Masonry Works” to allow for proper curing and to shift the masonry of the first floor closer to the masonry of the second floor.

2. Floor-by-Floor Activity Flow

• Justification: To optimize labor and avoid overlaps, sequential floors can be staggered using lags.
• Example: Add a 2-day lag between “Masonry Floor 1” and “Masonry Floor 2” to allow crew rotation.

If you want to learn more about scheduling techniques, you can enroll in our Construction Project Planning Intermediate Level with P6 course.

Conclusion

Minimizing total float within the construction WBS is a strategic approach to creating a more realistic and tightly controlled project schedule. By logically linking construction activities together and introducing appropriate lag times where needed, planners can better reflect the actual workflow, reduce unnecessary float, and enhance visibility into the sequence of execution. This helps ensure that the schedule is not only technically sound but also aligned with on-site constraints and construction logic. When total float is minimized through proper sequencing and lag management, critical activities become clearer, risks of delay are easier to identify, and resource planning becomes more efficient, ultimately contributing to more reliable project delivery.

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