There are an almost limitless number of things we cannot control. The past. The actions of others. Time. Sometimes, even ourselves.

Similarly, within the construction arena, there are many factors beyond our control—factors that can adversely affect a project. The weather, worker shortages, supply-chain issues and project revisions represent just a small fraction of these negative circumstances.

Fortunately, some project-risk issues are actually within our ability to control. One of the more impactful issues is the over-compression of project schedules. Over-compression of project schedules is far more common than one would think, typically resulting in considerable amounts of unnecessary costs related to inefficiencies, delays and disputes.

The construction industry has fought this problem for decades, as it results in billions of dollars in wasted spending yearly. That’s why it’s vital that all stakeholders on a project understand schedule compression: when and how it occurs, when it’s useful and how to recognize a schedule that’s over-compressed to the point of hindrance/negative effects.

Compression Defined

In simple terms, compression in construction occurs when the decision is made to complete the remaining amount of work in less time than originally planned. It usually results from decisions to push off future work with float or accelerate critical and near-critical path activities in an attempt to mitigate historical delays. It can also be the product of:

An unrealistic initial schedule

A poorly constructed schedule

Making up for a delay in resources

Change orders

A change in the delivery schedule

Rectifying a mistake

Changing client demand

If work is getting delayed, or pushed off, yet end dates aren’t changing, chances are compression is happening. It is crucial to keep an eye on compression; for example, by having a KPI that accurately estimates the extent of compression so better decisions regarding project acceleration can be made.

Compression of project schedules is common in construction because there are a lot of moving parts, budgets are tight and the execution of project activities rarely goes as originally planned. Not to mention the fact that the industry consists of optimistic people with engineering mindsets and can-do attitudes. And while it’s ultimately better for the overall health of a project to be realistic rather than optimistic, it’s tempting to set idealistic completion dates that will make everyone happy—even if they are unrealistic in the long run.

The truth is, incorporating compression into the construction schedule can be a very effective way to manage a project—if done properly. This tactic is common in construction because there are a lot of moving parts and things don’t always go as planned—so, in essence, compression is a necessity.

However, and unfortunately, most of the time compression is not managed appropriately, leading to over-compression—which can impact budgets, timelines, project quality, safety, even relationships.

There’s a fine line between managing acceptable levels of compression and creating mountains of over-compression; crossing that line can result in a project that goes sideways. Therefore, finding the compatible levels of compression within a project schedule is instrumental for project success.

Compression Methods

Compression typically results from changes to the schedule that are made using several different techniques, which include shortening activity durations, removing relationships between activities, and/or modifying calendars—all of which come with inherent risks.

By shortening schedule activities, one is committing to getting the same amount of work completed in less time. This can only be achieved by adding resources, extending the number of hours per day the crew is working or adding a swing shift—an additional crew that works outside normal working hours. The risks associated with adding resources is placing more people in a given area or committing to a time frame that may not be achievable if the resources aren’t available.

By removing relationships between activities or altering them to stackthe trades, one is either committing to putting crews of different trades in closer proximity together, or adding an entire crew to a single trade so double the amount of work can be done at the same time by working two different areas. The risks of putting the trades in closer proximity are a decrease in productivity, increase in quality risks and safety risks. The risks of adding an entirely new crew to the equation is committing to a time frame that may not be achievable if the contractor can’t get enough resources fast enough.

When modifying the calendars, one is committing to the current workforce putting in overtime, which can be particularly detrimental, as scheduling overtime results in decreases in productivity. A recent article on the website Construction Analytics presents the facts behind the loss of productivity due to scheduled overtime. What’s more, not only does overtime result in more hours with less productivity, but the cost of the overtime hours increases.

Calculating Compression

Calculating the level of compression in a schedule serves as a key indicator of risk associated with inefficiencies, delays, overruns, damages, claims and disputes and, ultimately, the reasonableness and viability of the schedule. The higher the level of compression, the greater the risk. So, it is in all stakeholders’ best interests to understand the compression of the schedule to ensure that acceptable compression levels exist. Focusing on this one metric alone could end up saving the industry billions in unnecessary spending.

Compression analysis is essentially a gauge of how much more work we intend to do in the remaining time left and then comparing that to the original plan. Therefore, in order to do this effectively, one must obtain and analyze project schedules, then perform the following steps:

Calculate the current earned percent complete on the project, as per the most recent schedule update.

Calculate the remaining duration of the project as per the most recent schedule update.

Calculate in calendar days by adding up the number of days between the data date of the most recent schedule update and the estimated project completion date as indicated in the schedule.

Determine the date in the original baseline schedule when the project should have achieved the earned percent complete that it had achieved to date as per the most recent schedule update.

Calculate the remaining duration of the project in the baseline from the date on which the project should have achieved the earned percent complete in step 3 and the planned completion date in the baseline schedule.

Divide the planned remaining duration calculated in step 4 by the current remaining duration obtained in step 2 to calculate the compression index.

Subtract 1 (or 100%) from the compression index to determine how much less or more time is allocated to completing the remaining work as compared to the baseline schedule.

If a project has less than 20% compression, that is acceptable; over 20% compression indicates an issue, because you and your team will need to work weekends or you need to increase the work output by 20% or more if you are not meeting your original planned productivity goals. If the compression percentage is even more than that, it becomes a resource issue where your field teams are expected to work more than there is time in a day.

It is important to note that compression is not only about critical and near-critical activities. It involves all the work being pushed out because of float, meaning you have to think about how to mitigate compression effectively by discussing the schedule with the people in the field. Doing this at every update allows you to right the ship, force the compression number to go down and get your project on track again. Otherwise, you will end up in a situation where you compress the schedule and then have to relax the end date further than the previous delays because of all the additional delays and inefficiencies that compression causes. The compression process begs several questions you want to consider together with your teams that tell a story about your project:

What are the schedule changes?

What is the extent of the changes and why are they being made?

Are the changes related to historic delays?

What changes surround the critical path?

Are the changes being made even possible, or are they being made to alleviate a difficult conversation?

Have the changes taken into account historical performance?

Do you have a plan to add resources, work overtime or on weekends to align with the changes?

Are you being overly compressed?

Having a compression process in which you are responsibly looking at the extent of the impacts caused is how you end up with better results. Adjust durations based on historical performance instead of compressing because if it wasn’t feasible in the past, it probably won’t be in the future. In essence, give yourself more time to complete activities than initially planned. Then, go into the field and work hard to achieve or beat the current end date rather than making an unfeasible, unreliable schedule.