Identifying Concurrent Delay

Mark Boe, P.E., PSP

Properly assessing concurrent delay can be one of the most difficult challenges encountered in resolving delay claims. First, of course, it’s essential to understand how concurrent delay is defined.

What Makes Delays Concurrent?

Simply stated, concurrent delay occurs when a contractor and an owner have both caused independent critical path delays — delays that affect the completion date of a project — during the same approximate time period. Consequently, barring a contract provision to the contrary, neither can recover damages without a clear allocation of each party’s delay and expense.

The most important question to ask in determining whether delays are concurrent is this: Are the individual impacts critical to completion? Often, hundreds of delays occur on a project that absorb “float” within the schedule, but do not ultimately postpone the completion date. Only delays that extend completion can be considered concurrent. These delay situations generally fall into two categories:

  • Multiple impacts to a single activity or path: In this case, one activity or event is affected by the actions of the owner and the contractor. For example, a contractor experiences delays in the supply of steel to a fabricator. The steel fabricator experiences difficulty getting shop drawings from a detailer and the owner initiates several minor changes to the steel. The intertwined relationship between these changes (or multiple impacts) makes delay apportionment very difficult.
  • Impacts to two or more critical paths: More commonly, concurrent delays involve impacts to two or more independent critical paths. For example, a contractor experiences delays in fabrication of structural steel. At the same time, the owner redesigns the foundations on which the steel will be set. In such situations, the timing of the delays determines whether apportionment can be made reasonably.

Delay situations become especially complicated when one party attempts to use concurrent delay as a shield against the opposing party’s delay damages. For example, an owner causes a critical-path delay due to late owner-supplied equipment. The contractor then asserts that the owner’s delay will result in both general conditions damages and extended home-office overhead damages. The owner responds that it is willing to grant the time, but that some of the contractor’s own delays (unspecified) were concurrent with the owner’s delays; and therefore, the delay costs are not compensable. It’s easy to see the problems that can arise here.

Where to Start

The proper evaluation of concurrent delay begins with the basic principles of any detailed critical-path schedule analysis. CPMI favors the contemporaneous method of schedule analysis because it provides a baseline for measuring delay, the status of the project at the time the delay occurs, and the impact of delaying events on the remaining work. It also provides insight into float, changes to the critical path, and revisions to the plan to complete. Once the delays are identified, concurrency is found if the following is determined to be true:

  1. The impacts are each critical to project completion
  2. The impacts are independent
  3. The time periods are the same (or very nearly so)

An Illustrative Case

Several years ago, CPMI was involved in a project to rehabilitate a medical laboratory that included a new HVAC system. The diagram (left) shows a summarized as-planned schedule. The critical path of the project began with demolition of ceilings (DEMO), which was scheduled to take a month and a half. The duct submittals and fabrication (PROCURE) were to proceed parallel, ConDelayChart400followed by the ductwork installation, which required two months, and then by building finishes. Early in the project, the owner discovered a significant design error that forced a complete redesign of the duct system. Update #1 shows that the project was on schedule when the design error was uncovered. Update #2 shows the status of the project when the redesign was complete. The contractor believed it was owed time and delay damages for a month and a half of delay. The owner countered that the contractor’s demolition work wasn’t complete until just prior to the ductwork installation; and therefore, the demolition was a concurrent delay.

Critical Paths: Our first step was to determine whether both impacts were critical. Evaluating additional time slices was one way to make this determination. As you can see from the lab building diagram, Update #2, the critical path on the day of the update proceeds through the start of duct installation and into building finishes. If a time slice is taken one day before the status date, the demolition activity and the completion of the duct procurement would both be critical (one day of delay to either the demolition or the delivery would delay the completion). If a slice is taken a week before the start of duct installation, the duct procurement activity would still be critical. However, the demolition activity would have almost a week of float here, since the remaining duration is only two days, but seven days time remains to complete the work. If you look at a time slice taken two weeks before the start of the duct, the demolition has almost two weeks of float (two days remaining duration, and 14 days to perform). Thus, the demolition impact did not cause critical-path delay to the completion of the project, it merely absorbed float.

Independent Impacts: For delay to be concurrent, the impacts must also be independent — that is, the impacts created by one party cannot be caused directly or indirectly by the other party.

In our medical laboratory case, even if the demolition work were deemed critical to project completion, the contractor may have reasonably claimed that the owner’s delay prompted it to re-plan the demolition work. In actuality, the apparent delay to the demolition work was the result of the redesign of the mechanical system. The delay would not have occurred if there were no redesign. When the contractor became aware of the redesign delay, it was not required to strictly adhere to the schedule when it knew that delay had occurred. A contractor is not required to “hurry up and wait,” but can reallocate its resources to take advantage of other delays. It should be noted, however, that when a contractor re-levels resources to utilize float created by an earlier delay, the decision must be documented to avoid after-the-fact allegations of concurrent delay.

The importance of knowing the specific facts of a project cannot be over-emphasized. Changing any of the details in this case illustration even slightly can completely change the outcome of the analysis. Referring to Update #2, if the reason for the contractor’s extended performance were weather, or equipment breakdown, or labor union slowdown, the as-built portion of the chart would look the same, but the delay could be considered independent; and therefore, the delay could be considered concurrent.

Time Periods: Timing is the third key determinant. Delays do not need to begin and end on the same day in order to be considered concurrent. In this case, the time period of the owner’s delay began before the contractor’s “delay,” but both delays ended approximately at the same time. If the owner’s delay to mechanical design was limited to one week and the contractor-caused one-week critical delay occurred the next week, the delay would be deemed concurrent even though there is no overlap, as the time period during which the delays occurred was reasonably close. However, if the owner’s delay occurred in the first week of the month and the contractor’s occurred in the last week, there would be room for interpretation as to whether the delays occurred in the same period. If the owner’s one-week delay occurred one month and a schedule update captured that delay before the contractor’s delay (say the following month), the time periods probably could not be considered concurrent. At some point between the first scenario and the last, the contractor can be said to be absorbing float created by the owner’s delay.


Distinguishing between delays that are concurrent and those that simply absorb float requires a thorough knowledge of the facts, an understanding of the basics of critical-path schedule analysis, and a determination of whether three key factors exist: 1) the delays are critical, 2) the delays are independent, and 3) the delays occur during the same time period.