Inside the Top Construction Scheduling Methods
October 13, 2020
Even when construction companies specialize in a particular type of project, it doesn’t mean all their projects are exactly the same. There will always be different requirements, timetables and resource availabilities to deal with. Because of this, it doesn’t really make sense to use the same scheduling method to manage them all.
Several proven scheduling options are popular within the construction industry. While each has its own capabilities, benefits and drawbacks, a common thread among them is that they each present schedules, workflows and task progress in relatively easy-to-understand visual formats. And many are supported by today’s advanced construction scheduling software.
But don’t think you’re limited to using just one. It’s actually common to rely on a combination of methods for different scheduling needs within a single project. Let’s explore some of the top choices.
Critical Path Method (CPM)
As one of the most detail-oriented scheduling techniques, CPM lends itself quite well to larger, more complex builds because it can account for the thousands of action items involved.
What is meant by a “critical path?” It’s a set of activities that must occur in a particular sequence in order to complete a project. This path, showing the steps before and after each task, illustrates the dependent relationships between tasks as a network or web, reflecting the duration of not only individual tasks but the overall project.
Start and finish dates and times are assigned to each task, allowing CPM’s algorithm to outline the critical path. The beauty of this method is it provides insight into the impact of a single schedule change on all dependent tasks.
With the critical path mapped out, project managers can determine how resources — such as labor or equipment — should be distributed for the highest level of efficiency. But because this method doesn’t directly address allocation, you may want to look at combining CPM with one of the other methods below.
Think of this type of scheduling as an RSVP system for project resources. The idea here is to allocate limited yet high-demand resources — such as equipment, labor or office space — where they’re most critically needed across the project life cycle. Scheduling is based on priority rather than time in this instance.
This prioritizing helps maintain productivity as it reduces project bottlenecks and the delays that often come from waiting around for unavailable resources. And there’s less likelihood of being forced to secure extra resources on short notice; an activity which often comes with a premium price tag.
Resource-oriented scheduling would make a good companion to CPM to account for resource allocation, yet it can become unwieldy if too many resources need to be allocated. In addition, it may not work quite so well for projects in which resources are required for simultaneous activities. However, it is ideal for smaller projects with few resources to assign as a way to keep projects moving forward while reducing delays.
Line of Balance
Maybe you have a project that involves blocks of repetitive work — road construction, tunnels, multiple dwelling units, etc. — as single activities within your project. Similar to the priority-based purpose behind resource-oriented scheduling, the line of balance method uses a line graph to show how resources are distributed according to the order in which they’re needed on the job site.
Visually, the graph for this method is often represented by a series of upward-slanting lines, with X and Y axes measuring variables such as unit quantity, time or cost. The distance between these individual lines indicates the variance in the rate of completion of a particular activity rather than duration of time. Maintaining equal distance means things are going smoothly at a steady pace and are on track for on-time completion, while widening distances reveals a slowdown in the process that could impact subsequent activities and resource availability.
While perfect for tracking individual tasks at a glance, just be aware that it doesn’t provide the level of detail that CPM does, which is why it often makes a nice companion to CPM.
Perhaps the simplest and most recognizable of the scheduling methods, bar charts map out on a timeline the start, duration and end of a project (or portion of it). Bars can be stacked vertically to show the individual resources necessary to complete a certain task.
So, if you like the detail behind CPM but prefer something simpler, a linked bar chart connecting current tasks to previous and subsequent ones will provide a clear display of what has to be done before another activity can begin.
Within this broader category are several other well-known breakout bar charts:
Gantt charts are horizontal lines, or bars, of varying lengths plotted along a timetable. Anchored by the start date and ending with the finish date, each line represents a specific task’s duration to complete. Each can fall under a bigger task, indicating a hierarchy of activities for a certain part of the project. Much like CPM, Gantt charts can show relationships to other tasks, with linked predecessor and successor activities, but not with such a fine level of detail. And it’s able to account for resource allocation, a known limitation of CPM.
One of the strengths of a Gantt chart is its at-a-glance flexibility. If a client or high-level stakeholder wants to gauge overall progress, they’ll be able to pan out for a broad project view. Similarly, for anyone needing a more granular view, zeroing in shows a narrower timeline and more specific tasks. For even more detail, progress bars indicate the completion percentage of a task, giving insight into potential delays and providing an opportunity to take corrective action.
It’s not just the site crews that have to be at a certain point at a certain time. All the different materials they’ll need must be there as well. And that’s what Q (or Quantitative) scheduling tracks. By focusing specifically on materials scheduling, contractors can ensure everything is ordered and delivered on time where and when it’s needed.
Even though it is another bar chart method, Q scheduling is also quite similar in purpose to line of balance scheduling with its focus on materials distribution, though it’s not based on task repetition. So, it’s applicable in most construction projects.
“Q” also has another meaning, as in queue. In this usage, Q scheduling revolves around intentional sequencing of specialized or trade work activities so there’s no interruption from overlapping schedules, which often trigger delays and create extra costs. In fact, it’s the only scheduling technique that tracks costs related to the job sequence.
As you consider which scheduling methods will work best for your projects, keep in mind the construction scheduling software you use to run them is equally important. InEight’s planning and scheduling software enhances project predictability and performance at the same time. Plus, it integrates with our entire suite of software solutions created especially for the construction industry to make your build more successful.