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

In project planning, there is no absolute right or wrong approach, only strategies that best fit the project’s requirements. When managing shop drawing submittals in Primavera P6, planners often debate whether to link submittals as activities or use lag time before the related milestone. Both methods are valid, but the key lies in knowing when to apply each approach based on the consultant’s requirements and project constraints. This article explores the advantages and drawbacks of each method, helping planners make informed decisions to ensure accurate scheduling and smooth project execution.

Why We Should Delay the Shop Drawings Submittals in the First Place

In mega projects or projects with complicated details, the number of required shop drawings can be substantial, covering various disciplines such as structural, architectural, MEP, and specialized works. Given this volume, it is unrealistic to assume that all shop drawings will commence during the initial stages of the project within Primavera P6. While some critical submittals, like structural and foundational drawings, must be prioritized early to avoid construction delays, many others will follow a phased approach aligned with the project’s execution sequence.

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Attempting to schedule all submittals at the start can lead to misleading float values, unrealistic resource allocation, and inefficient tracking. Instead, shop drawing activities should be carefully phased and linked to the corresponding work packages, ensuring logical sequencing, consultant review periods, and procurement timelines are all accounted for.

No contractor will submit all the shop drawings once the project starts. It is more realistic to submit the shop drawing before the date of the construction activity for this shop drawing. for instance, the curtain wall that will be installed at the end of the project should have the shop drawing submittal right before installing, not several months in advance (when the project starts). This will be a waste of resources in the technical office and poor coordination to decide the project’s priorities.

When to use lags and when to link Shop Drawing Submittals with each other

1. Lags between Start and Shop Drawing Submittals

Lags can be used when the client and the consultant agree that lags are accepted in the time schedule or even accepted with a percentage of the whole time schedule.

The concept of using lags is that it delays the activity right before the construction date, leading to a decrease in the float number, but right before making the activity critical.

As can be seen above, the “Fire Extinguishers” will start as a construction activity later in October. Meanwhile, on the schedule, we will be submitting the shop drawing later in February, leading to a high float in the schedule.

We can add lag between the start milestone activity and the shop drawing submittal to decrease the float and shift the engineering phase nearer to the construction activity.

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You can learn more about how to add lags to all submittal activities as a bulk from this article, The Application of SF Relationship in Primavera P6

2. Linking Shop Drawing Submittals with each other

If lags are not accepted at all in the schedule, some planners use this method to decrease the float and provide a more realistic shop drawing submittal plan, which is linking the submittals with each other to decrease the gap between the construction and engineering without changing the date that the construction should start on.

Since the first construction activity with a shop drawing submittal is the “Inspection Chamber” activity, this will be our starting submittal activity.

We can link the submittal of another activity that will start soon to the “Inspection Chamber” to shift it.

We will repeat this step several times till we reach something like this.

Some clients and consultants refuse this method because if a shop drawing is delayed or rejected and enters the resubmission phase, it will delay all the successor drawings, which is not logical.

For instance, if the “Inspection chamber submittal” activity was delayed, and we had assigned the “handrail submittal” activity as a successor to it to decrease float. The “handrail submittal” will be delayed and affect the project, when in fact, the handrail will be installed later in the project, so its shop drawing should not cause any problems during the initial stages of the project.

However, if it is not totally refused, you as a planner can link them according to the sequence of work while respecting the delay that may happen, so you don’t link submittals that are not related or submittals that are exactly after each other so that the appearance of a delay can be less risky.

Justifications for Both Methods

If it is allowed to use any method, but you must provide justification alongside the submitted schedule, you can use the following justifications for both methods.

Linking shop drawing submittals with each other: the capacity of the consultant’s technical office. The technical office should receive a specified number of shop drawings during a specified period to finish them and avoid delays in the project, and smooth workflow.

Adding a lag between the shop drawing submittal and the start milestone: according to the available total float and levelling, and the number to be submitted in a specific period. We can add lags to shift the activity in a specific period to reach the specified number of submittals in a period, but within the frame of the available total float.

Conclusion

Whether to link shop drawing submittals as activities or use lag time in Primavera P6 depends entirely on the project’s complexity, consultant requirements, and the need for accuracy in scheduling. There is no single rule in planning, each project demands a tailored approach that ensures the schedule remains realistic, manageable, and reflective of actual workflows. The key is to choose the method that best represents the approval process while maintaining logical sequencing. By understanding the advantages of both approaches, planners can make informed decisions that support efficient project execution and avoid unnecessary scheduling risks.

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