The Importance of Constraints Removal

In construction scheduling, constraints are anything that prevent a task from being completed. These often cause a project to fall behind schedule and run over budget. It is important to work to remove these constraints in the planning process to avoid repercussions.

In this article, we focus on an important aspect of the Last Planner System®: the constraints removal process.

Background on Constraints 

In a previous blog about pull planning, we briefly touched upon the four phases of the Last Planner System: Should, Can, Will, and Did. Pull planning fell into the Should category, while constraints fall squarely into the Can phase, and is a crucial element of the make ready planning that occurs before execution begins.

Briefly defined, constraints are anything that can keep a task from being completed. Make ready planning generally breaks these down into three types: schedule, time, and scope constraints.

  • Schedule constraints are anything that have an effect on the time it takes to complete a project.

  • Cost constraints relate to materials, labor, and equipment

  • Scope constraints are about the overall goals of a project.

Constraints are interdependent. For example, if time constraints are not documented and removed, they begin to create problems that affect cost, force labor overages, and ultimately impact the overall scope.

Identifying and documenting constraints

To prepare for removing constraints, you should start by asking yourself a few questions:

  • What are some things that can keep your project from being successful?

  • Are there ways to plan for things that can hold up your project?

  • How do you develop a sound process for making a project ready for execution?

To help explain this process, it’s helpful to use a concrete example. Let’s say that a project was taking place in a town with strict zoning laws where permits are required for working in certain areas. This can be a time-consuming process but is obviously crucial, and highly dependent upon others. A city permitting office may give itself a certain period of time, say 30 days, to turn a permit around, not to mention the time preparing to submit the required paperwork.

This would be identified as a scheduling constraint and recorded in a constraints log. In this log, the constraint would be given the earliest date that the constraint removal process could begin, as well as the latest date for this to be done without affecting the start of execution. Since it’s unlikely that there is only one permit to obtain, this log could have overlapping dates. Software that includes a constraints removal process simplifies this process significantly.

Assigning responsibility

Now that the constraint has been identified and documented, who is responsible for removing it? Ensure responsibility is assigned to tasks as they are identified so that no task gets lost in the shuffle.

Removing constraints

When all tasks associated with a constraint are recorded, scheduled and assigned, removal of the constraints can be a rational way that looks ahead to smooth execution. You may find that in the midst of this process, other constraints may be uncovered or may develop based on external circumstances. To address this kind of situation, it’s important in the “Can” phase to continue to meet on a weekly basis to update the constraints log.

We created a checklist to make this easier. With this checklist, you’re able to document constraints for a project, assign responsibility and identify important dates. Utilize this download to avoid projects running over budget and behind schedule.

Technology for improved productivity

Software, such as TLMS® by Trestles, that is based on the Last Planner® system has the power to help you track your constraints on a constant basis and may mitigate the need to have so many meetings. Meetings are not a bad thing when they serve an important purpose, but we could all benefit from spending less time in meetings and more time doing the work that will move execution along and help finish a project on schedule and on budget.

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