Concurrent schedule delay

Published by Massimoluigi Casinelli on

a brief introduction

The situation of concurrent schedule delay is very common in construction, where many “contractual parties” are involved.

There are specific technquines: schedule delay analysis to evaluate the “schedule delays” and assess the Extension of Time (EOT).


  • For claim management it is necessary to identify the causes and the contractual party which actually caused the schedule delay, and to assess such delay.
  • In the majority of cases the delay is caused by concurrent events, i.e there is a “concurrency” of causes, occuring at the same time-period.
    • This type of “delay” is named concurrent schedule delay, which is the most common but even the most difficult to analyze and manage.

As generally recognized by the claim experts,  when “ planning & scheduling” is well addressed in the Contract, the schedule delay analysis is certainly facilitated; the contract therefore plays a central role, by addressing specific matters like the ownership of total float and the techniques to be used in “schedule delay analysis”.

The problem of concurrent delay is complex and it entails other related issues as “total float management” . In literature various techniques are used perform such as schedule delay analysis, among those the following are generally referred. It’s assumed that schedules are CPM based.

The specific event (causing a potential delay) is described by a single sequence of activities named  “fragnet” (fragmentary network).

For practical examples we consider in the following description that the “event” is a PCO (Potential Change Order). regarding a PCO (Purchase Order).


The techniques used to analyze and “measure” the concurrent schedule delay are the same of those adopted for schedule delay analysis:

  1.   As- planned versus as-built comparison method

The as-planned is the original approved baseline schedule and as-built schedule depicts the actual sequence and progress of the activities, as they occurred in the project execution. 

The “as built schedule” is the “current schedule update”, if a good procedure for schedules updates has been implemented !

  • The impacted as- planned (baseline) method

The singles fragnets of PCOs are inserted in the original baseline schedule to evaluate and analyze the impacts on critical path(s).

  • Contemporaneous period (windows) analyses

This method uses the periodic schedule updates (i.e current schedule updates) to determine the effects of PCOs occurring during the course of project. The analysis is undertaken by inserting the “fragnet” in the “current schedule update” relevant to the current time -period at which the PCO(s) occurred or is proposed. By using this method, it is crucial to determine which the schedule update version that can be used and this should be obtained with the Owner’s approval.

  •  Collapsed as-built schedule

The collapsed as-built schedule method is a variant of the “contemporaneous periods” method, where the analysis is undertaken by “collapsing” the as-built schedule, i.e. extracting the fragnet of PCO(s).


Using methods 3 or 4 above described, a good process is:

  1. get approval by the Owner of the specific/s fragnet/s proposed;
  2. get approval by the Owner of the “current schedule update(s)” relevant to the specific period(s) for which it’s necessary to perform the analysis;
  3. inserting the fragnet in the schedule and running scheduling to evaluate the impacts,
  4. including specific reference to letters, RFIs and any other reference that could prove and document the “events” described; specific comments and notes should also added to the activities of the schedule, using specific tools in Primavera.
  5. preparing a concise and clear narrative report,
  6. presenting findings to the Owner trough a professional presentation, having “to hand loading” the backup of any referenced document (letters, RFI etc).


The above brief description of the techniques used to analyze “project schedule delay” should lead to these final considerations:

  • Which is the “as built schedule”?  What happens if we use an as built schedule which is not accepted by the Owner? The “as built schedule” should be thecurrent schedule update”, and this is possible only if a good procedure for scheduling and updating has been implemented at Programme level ; this entails that the Contact properly rules the project planning and scheduling system, trough effective Programme/Project Planning and Scheduling Contractual prescriptions.  
  • Which method (among the above described) should be used to analyze the concurrent schedule delay? Before running into the comparisons of the techniques, we should recognize that, first of all, the Contract should clearly address these issues, through the contractual prescriptions, but this clearly a tpoic of another post;
  • It is evident that it is therefore necessary to have a clear understanding of the whole project management processes and the Owner should carefully address these issues during the Strategic project planning phase by designing the whole contractual framework.

I would be happy to receive your comments or specific questions.

Thank you

Digiprove sealCopyright secured by Digiprove © 2020 Massimoluigi Casinelli

Massimoluigi Casinelli

I am a chartered civil engineer and certified CCP (cost engineering and total cost management) at AACE International, with thirty years of experience in project management of the construction sector. I deliver expert planning, programme management and project controls on multibillions-Euro infrastructure programmes, including highways and railways, metro, air terminals and complex buildings (commercial, residential, schools), with some experience in oil & gas and power. I worked in advanced contexts of project management (from matrix organizations of EPC contractors to large employers organized to manage complex capital projects), by undertaking various roles in the field of project management / controls and contract management; this diverse range of experiences allowed me to gain knowledge on the various components of project controls (schedule, cost estimating, budgeting and cost control, progress and performance measurement, risk and claim management). I am an Italian citizen, currently in Italy.


Leave a Reply

Avatar placeholder

Your email address will not be published. Required fields are marked *

error: Content is protected !!