Building an accurate and reliable construction schedule is one of the foundational aspects of managing a construction project. Whether you’re working on a large capital infrastructure project or you’re just simply building a house, you need a good construction schedule to understand and achieve the project’s key milestones. In addition, a construction schedule provides insight into varying labor demands at different points in the project, as well as when certain subcontractors need to be on the job site to begin their work.
The construction schedule is so important that it’s often included in the contract documents, making it legally binding. For the owner, the construction schedule allows them to plan on when a project can be occupied and can start generating revenue. It also helps them manage a broader portfolio of projects and plan resources accordingly.
An effective construction schedule allows you to finish the job before the original completion date, reducing your General Conditions on the project and maintaining a good relationship with the client. A poorly crafted construction schedule has the potential to delay the project’s completion, put you at risk of incurring liquidated damages, and can ultimately cost you substantially more money if claims arise from the project.
We’re going to take a look at what goes into making a good construction schedule, some of its key components, and how you can start taking control by building better schedules on your projects today.
The Building Blocks of Scheduling
As we begin to look at some of the fundamentals of a good construction schedule, there are a few basic terms that you need to know to get started on the right (critical) path:
- Work Breakdown Structure (WBS) – The work breakdown structure, or WBS as it is often referred to, is core to building any schedule. The goal of the WBS is to capture 100% of the work included in a project’s scope and break it down into smaller, more manageable elements. Once you do that, you can begin to see how the different activities relate to one another and start to build the schedule. The larger groups within work breakdown structures are known as tasks (design, permitting, construction, different phases in construction). Then one level deeper, those tasks are divided into smaller groups to create subtasks (within the construction phase, demolition, earthwork, concrete, etc.). Finally, the next level of division is called a work package, which is the last level you’ll break down an activity on the main project schedule. This is the level where you will start to connect with other related activities and estimate the time it will take you to complete those work packages, and how that affects other work packages.
- Work Durations – The estimated time to complete an activity within the schedule from start to finish is referred to as duration. Duration applies to all three levels of the WBS, but is typically examined at the work package level, because when two work packages are related to one another and one is delayed, it has the potential to cause a cascading series of downstream effects that can delay the entire project.
- Dependencies – In addition to duration, how the two different work packages are connected and affect one another is also extremely important. For example, before you can place the concrete foundation, the earthwork needs to be completed and the ground needs to be compacted and prepared. If heavy rains delay the earthwork from completing on-time, then it will affect the start time of the concrete, and the effects will continue to be felt throughout the rest of the project.
- Float – Think of float as padding or cushion within an activity’s planned duration. Continuing on the example from before, the heavy rains delayed the earthwork and delayed the start of the concrete, but if you have float (or extra days) included in the duration of the concrete activities, the initial delay may not be that bad, as long as the float is accurate and the activity can actually be performed faster than what it was scheduled for.
- Lag – This is the wait time to start one activity after another one has been completed. Now that the concrete foundation has been placed, there is a certain time that it has to cure before the project can start building on top of it. This is an example of lag. Often, lag is unavoidable, but in some circumstances it can be mitigated by good, logical scheduling.
- Baseline – A baseline schedule refers to the original schedule at the time that the project started. Baseline schedules are extremely important because they provide a consistent initial point of reference for future schedule modifications. Construction schedules are iterative documents, with few construction schedules ever escaping changes or updates throughout the project. As the schedule morphs and molds to the various conditions affecting the work, the baseline helps you understand the original plan and allows you to compare revisions and see how different situations affected the construction progress.
- Lead time – Lead time is another especially important aspect of scheduling, because it serves as the difference in time, or the delta, between when you plan to start an activity and the current moment in time. Lead times play heavily into material procurement. At the beginning of a project, it is important to identify any materials that have long lead times (i.e. they take a long time to deliver from when you initially place the order) and place special emphasis on making sure those materials are ordered. Missing the right materials when an activity is slated to start can cause serious delays in your schedule.
- Milestones – These are the dates when certain parts or portions of the project are expected to be completed and serve as the goal posts on a construction schedule. They are usually associated with subtasks or larger tasks, but can be associated with a work package of high importance on a project.
Understanding these critical aspects of scheduling are key to constructing a logical, efficient, and streamlined construction schedule. Once you have a good understanding of these fundamentals, the next step is creating a construction schedule.
Means and Methodologies: 4 Schedule Approaches
There are four main methodologies that can be used exclusively or in conjunction with one another to create the construction schedule, and each methodology approaches dealing with risk slightly differently. The four methods are:
Critical Path Method (CPM)
This method is based solely upon looking at the Critical Path activities within a construction schedule and relying on the duration and sequencing included in the schedule to steer the overall ship of the project. The CPM method provides a comprehensive level of understanding of the relationship and is usually used in conjunction with a Gantt chart to visually display the schedule activity durations and relationships. Relying solely on the CPM to meet all of the scheduling needs of a project is often unrealistic, depending on the level of complexity of the work, and is often used in conjunction with the LPS.
Last Planner System (LPS)
The Last Planner System is a method that puts the scheduling responsibility in the hands of the field worker, the foremen and forewomen, frontline managers, and the superintendents who know their specific scope better than a scheduler and have the experience to accurately estimate durations and coordinate with other subs to complete the work in the right order. This system works well for granular scheduling activities, like coordinating 3-week look ahead schedules and pull planning, which capture the details for the specifics of the work activities at a level that is too zoomed in for the CPM to capture. The Last Planner System and pull planning are both part of the larger effort of LEAN construction, which is a practice that seeks to optimize construction through reduced waste and refined processes.
Program Evaluation and Review Technique (PERT)
PERT is a method that uses schedule durations of activities and takes a statistical approach to handling risk of delays in the schedule. It does this by taking a weighted value of the shortest, longest, and expected durations associated and averaging them together. This is an effective method if there is a high degree of uncertainty in certain activity durations.
Line of Balance (LOB)
Line of Balance is a technique that works well for projects that contain several repeating iterations of the same sequence of work activities. Think of projects like a gas line installation or building a skyscraper. These projects rely on the ability of the resources needed to complete the repeating sequence (i.e. labor, subcontractors, equipment, materials deliveries, supply lines), to work in a cascading way. Line of Balance accomplishes this by focusing on allocation of resources and the associated effects on production rates, to find the most optimal and efficient path to project completion.
I have found the most challenging projects typically require the project management team to be well-versed in using multiple methodologies at the same time to effectively schedule and plan the work. The key is making sure you use the right method at the right time to maintain Critical Path and to keep your projects on schedule and avoid costly delays, or worse.
👉🏻 Read Foundations of Construction Management for SMBs
Critical Path: Shortest Route in a Long Race
The importance of the Critical Path cannot be overstated. I’ve mentioned the gravity it holds in a construction project, but let’s dive deeper into what it actually is.
The Critical Path can be described in several different ways on a construction schedule, but imagine it as a connected pathway across the different activities and relationships that represents the shortest possible time the project can be built in, if there are no delays. While the different methodologies mentioned previously can be used in conjunction to develop construction project schedules, they all respect the power of the Critical Path.
Knowing the Critical Path within the interconnected relationships of all of the activities on a construction schedule is probably the single most important factor in any construction project. Any activity that is a Critical Path item should be scrutinized to avoid any delays to that activity’s duration, which would affect the entire project’s duration. Similarly, any activities that the Critical Path activities are dependent upon within the schedule have the potential to delay the Critical Path if they finish late or somehow affect the critical path activity.
Most construction scheduling softwares will calculate the Critical Path for you, but the calculator is only as good as the accuracy of the information within the schedule, so make sure you have:
- Realistic durations and resources to perform the work.
- A clear understanding of what sequence the work has to be performed in.
- Solid relationship logic between the various activities within the project.
- Reliable subcontractors that can meet the schedule obligations.
The Critical Path serves as a North Star, guiding you through the project in the shortest time possible. If you don’t pay close enough attention to the Critical Path and don’t plan and allocate resources accordingly, you will feel the consequences. Costly liquidated damages, extended General Conditions costs due to being on the site longer, and potential liability in claims relating to the project can result from mistakes that could have been prevented by monitoring and protecting the Critical Path.
Proper Planning to Mitigate Common Schedule Risk Items
Construction schedules are full of potential risk items that can upend a project, or even a company, financially. While it’s not always possible to eliminate all risk, there are several common risks to project schedules that can be planned for to reduce the risk of delays:
- Weather – Heavy rain, wind, flooding, ice, and other natural events represent a frequent source of challenge and risk to delaying the project schedule. While there is a high degree of uncertainty knowing what natural events may occur, you can plan effectively in preparation to overcome challenges that weather would normally pose. Understanding what the weather is like at different times in the year where you are building your project will allow you to factor historical weather patterns into your activity durations. Similarly, having a cold-weather concreting plan ready for chilly conditions helps you make sure to have the right tools, equipment, and supplies that are needed if you have to place concrete when the temperature drops.
- Long-Lead Items – Activities on the schedule that depend on materials with long lead times are one of the first schedule risks most project management teams will be forced to contend with on a project. If a submittal is missed or there is any delay in placing the material order, the entire project schedule is at risk of being extended. Making sure that you thoroughly understand the specifications, focus on the details and make sure your material order is placed on time and is correct, and continue to follow up with the vendor to make sure that everything is on track delivery time are proven ways to ensure your long-lead items don’t cause delays and affect your Critical Path.
- Incorrect Work Sequencing – If work activities are scheduled in an order that doesn’t work when they are getting built out in the field, problems will quickly arise that can affect the Critical Path of the project. You can mitigate this by making sure the schedulers understand the work sequencing and, if there is a scope that they don’t understand, refer to either a field leader that has more detailed knowledge on the order of completion of that scope.
- Inaccurate Durations – This also has the potential to really cause chaos on a project, especially when multiple contractors have dependent scopes and it causes cascading effects when one is delayed. Getting continual updates from subcontractors on their labor availability and knowing your historical production rates will make sure you have a clear understanding of how much time is needed to complete each activity on the schedule, whether you will self-perform or subcontract that activity out.
How Scheduling Can Make (or Break) Your Company Financially
All of the different aspects that I’ve covered boil down to one basic fact: the importance of the schedule to a project and how much power it has to affect the project and the company financially. Here are some of the bad and good things that stem from a project schedule.
The Bad
- Liquidated Damages – These are penalties for not reaching certain milestones in time due to a delayed schedule. These fines can become very expensive very quickly, especially when dealing with the closure of any public infrastructure. The fines can sometimes be charged in increments of every 15 minutes until the milestone is met.
- Extended GCs – An extended schedule means you are on the project longer, which means that you are spending more money on office space, equipment rentals, and soft costs associated with keeping the project running. These costs, again, add up quickly and represent risk to the company until they can be closed out.
- Claims – Often, legal disputes can arise from schedule delays, especially when dealing with public infrastructure. These costly court battles can last for years after a project is finished and the only true winners in the process are the lawyers.
The Good
- Value Engineering – You can present a value engineering option to the owner that could potentially increase labor productivity or reduce unnecessary work. That could save you on reduced General Conditions and even save you on materials. There are a lot of positive financial benefits to incorporating this practice.
- Reduced GCs – Less time on site means less costs to keep the project office going. This reduction can be substantial on a big project and means your company will enjoy better overall profitability.
- Improved Client Relationship – Hitting milestones and making all efforts to avoid schedule delays can help to develop a very good relationship with the client, who will likely appreciate the efforts to finish the work on time. This will likely lead to a better relationship and more business in the future.
Construction Scheduling — Key to Effective Construction Project Management
The importance of building a good schedule for your construction project cannot be overstated. Keeping a tight level of discipline and attention towards the schedule will pay dividends in making sure your project gets completed on time. While good scheduling takes a lot of work to do well, the consequences of what can happen when you don’t have a good schedule are definitely worth avoiding.