Construction delays chapter six delay analysis using bar chart schedules

CHAPTER SIX

Delay Analysis Using
Bar Chart Schedules
Later in this book, we will explain how to perform a delay analysis when
a detailed Critical Path Method (CPM) schedule was created as the original as-planned schedule for the project. However, many projects are
scheduled using a bar chart schedule (bar chart). For projects with many
interrelated activities, a bar chart is not as desirable as a CPM schedule,
because a CPM schedule records and preserves the relationships among
the activities. However, a meaningful and accurate delay analysis can still
be performed using a bar chart. With any schedule, as the level of detail
and the quality of information decrease, the delay analysis becomes more
subjective. Therefore, a delay analysis that is based on a bar chart requires
the analyst to guard against assumptions that favor one outcome or another
and to work to be as objective as possible. This chapter describes how a
delay analysis is performed when the project schedule is a bar chart.
There is nothing inherently wrong with scheduling a project with a bar
chart. Bar charts were in use long before the Critical Path Method was ever
created. As some professionals are quick to point out, the Empire State
Building was scheduled with a bar chart and not a CPM. In fact, a detailed
bar chart can provide almost as much information as a CPM schedule.
Fig. 6.1 is a simple bar chart for the construction of a bridge. Though
it does not contain a significant number of activities, it does show the
general sequence of work for the construction of the bridge. Using this
simple bar chart as a starting point, the project manager could easily
define each activity in more detail.
Fig. 6.2 is a more detailed bar chart of the project depicted in
Fig. 6.1. This more detailed bar chart more clearly defines the contractor’s
proposed work plan. In this bar chart, each major activity is broken down
into the work on the respective piers and spans, providing the contractor
and owner with a more detailed illustration of the plan for construction.

With very little effort, the project manager or project scheduler can
modify the bar chart in Fig. 6.2 to show the interrelationships among the
activities, as shown in Fig. 6.3.
Construction Delays.
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Figure 6.1 Simple bar chart example.

Using this schedule as a foundation, a CPM schedule for the project
could be produced with little effort.
Unfortunately, most bar charts for projects do not contain as much
detail as that in Fig. 6.3, and often not even as much as the bar chart in
Fig. 6.2. In general, most bar charts suffer from the following major
shortcomings that diminish their usefulness as a management tool and
their effectiveness in measuring delays:
• Lack of detail—too few activities for the amount and complexity of
the work
• No indication of the interrelationships among the activities
• No definition of the critical path of the project
Obviously, these weaknesses hamper the ability of the analyst
to perform a delay analysis, but they do not make it impossible. If nothing

else, the bar chart is helpful in that it defines the plan for constructing the
project, and it can be used as the basis for an analysis of delays.

DEFINING THE CRITICAL PATH
The first step in analyzing a bar chart is to define the critical path.
Every project has a critical path, including a project that was scheduled
with a bar chart. The following definitions illustrate this point.


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Figure 6.2 Example 1 detailed bar chart example.

BASIC CRITICAL PATH METHOD
In CPM scheduling, the drafter of the schedule prepares a logic or
network diagram. As presented in Chapter 2, Float and the Critical Path,
once durations are assigned to the activities in the network logic diagram,
the critical path can be calculated. It is a purely arithmetic process.


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Figure 6.3 Example 1 detailed bar chart example with logic relationships.

The definition of the critical path is the longest path of work activities through
the network diagram that forecasts the date when the project will finish. The project cannot finish until every path of work has been completed. Whether

the critical path is defined in a CPM schedule or a bar chart, every
project has a series of interrelated activities that will control the project
completion date.


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Also, the only way to delay the project is to delay an activity on the critical path of the project. In understanding this concept, it is essential to recognize that the critical path of a project is dynamic. In this manner, delays
to noncritical activities that persist will cause the critical path to shift to the
path containing that activity and, thus, will then delay the project.

IDENTIFYING THE CRITICAL PATH ON A BAR CHART
Because we know that a critical path exists in a bar chart schedule,
the delay analyst should first identify this critical path. The analyst must
review the bar chart in detail for obvious conclusions about the sequence of
work. These conclusions may be based on project documentation that
might clarify the thought process that went into creating the bar chart or
defining the planned work sequence. Documentation that can be helpful
includes the contract, which may dictate staging or phasing, the pre-bid or
preconstruction meeting minutes, internal contractor or subcontractor documentation, project correspondence exchanged before the bar chart was prepared, and any other documentation that might shed light on the how the
project team approached the planning and scheduling of the project.
Practical knowledge of the type of project and the physical construction requirements is also necessary to reach a reasonable conclusion
regarding the project’s critical path. For example, to analyze a bar chart of
a high-rise structure, the analyst may need to know that interior finishes
usually are not planned to start until the building or a portion of the
building is “dried-in” or “watertight,” that a common sequence of the
progression of trades is from the bottom up, and that it is common for
trades to follow behind one another as the building progresses upward,

instead of waiting until the preceding trade has finished all of its work in
the tower.
Given the variations in possible work sequences, analysts should resist
the temptation to interpret the bar chart schedule based solely on their
own experience. Just because a contractor has performed work in a particular sequence in the past does not mean that the contractor on the
project being analyzed has planned to perform the work the same way.
Unless the bar chart is extremely brief, analysts should be able to glean
the best indication of the overall plan and sequence of activities to


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Figure 6.4 Identification of initial critical path activity.

determine the critical path using the bar chart as the primary indicator of
the project team’s plan for execution of the project, rather than analysts
proposing their own version of a plan.
Referring to Fig. 6.3, we can define the critical path for the sample
bridge project. The critical path starts with the mobilization activity, with
a duration of 2 weeks. This is obvious, since no other activity is scheduled
to occur during this period. We show this first critical activity in Fig. 6.4.


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The next two activities on the schedule are the clear and grub activity

and the piles at Pier #1. In reviewing the sequence of activities, the clear
and grub activity is related to the abutment and approach work. The
abutment and approach work is scheduled to finish well before the end of
the project and does not appear to be related to the schedule of activities
for bridge construction. The analyst can determine from the contract that
the approaches are to be constructed using asphalt paving, but the bridge
deck is to be paved with concrete. Consequently, there is no physical reason to coordinate the concrete placement for the bridge with the
approach construction. The only possible relationship might be the need
to move the concrete placing equipment onto the bridge superstructure.
However, because the schedule reflects that the deck work is to start
before workers complete either of the approaches, the analyst concludes
that the equipment can be moved onto the bridge independently of the
approach work. Therefore, it appears that the abutment/approach path is
not on the critical path for the project.
Therefore, the critical path must be through the piles and piers. When
viewing this bar chart, the analyst sees that the work is “stair-stepped”
through the specific activities for each pier. Thus, after the piles at Pier
#1 are completed, the piles at Pier #2 can start. While the piles at Pier
#2 are being driven, the pile cap at Pier #1 is concurrently constructed.
Based on the graphic representation, the critical path appears to follow
these activities (shown in Fig. 6.5):
• Piles, Pier #1
• Pile Cap #1
• Pier Column #1
• Pier Cap #1
At this point, the analyst recognizes that the pier columns and the pier
caps each have 2-week durations, and the next activity—steel erection—
does not begin until all pier caps are completed. Therefore, all pier column and pier cap activities are most likely on the critical path, not just
the first piles, piers, columns, and caps. Using similar reasoning, the steel
for Span #1 is critical, and then the path continues through deck placement for all spans. Next are the curbs and sidewalks for Spans #3 and #4

and, finally, the punch list work.
Thus, the overall critical path from the bar chart (Fig. 6.6) is:
• Mobilization
• Piles, Pier #1
• Pile Cap #1


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Figure 6.5 Identification of initial 5 critical path activities.

•
•
•
•
•
•

Pier
Pier
Pier
Pier
Pier
Pier

Column #1
Column #2
Cap #1

Column #3
Cap #2
Cap #3


Delay Analysis Using Bar Chart Schedules

Figure 6.6 Identification of the critical path.

•
•
•
•
•

Steel Span #1
F, R, & P, Span #1
F, R, & P, Span #2
F, R, & P, Span #3
F, R, & P, Span #4

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•
•

•

Curbs & Sidewalks, Span #3
Curbs & Sidewalks, Span #4
Punch list
The analyst could reach a similar conclusion working with the less
detailed bar chart alone (see Fig. 6.1). This would, however, require that
the analyst make more assumptions about the work on the separate piers.
As was noted in the preceding discussion, contemporaneous documentation can help the analyst define the contractor’s planned sequence in
more detail. The less detailed the bar chart, the more assumptions are
required by the analyst to determine the project’s critical path.

QUANTIFYING DELAYS USING BAR CHART SCHEDULES
The process of quantifying delays using a bar chart is similar to the
process that is described later in this book when a CPM schedule is available. To start the process, the analyst must prepare a detailed as-built diagram that shows as specifically as possible when the project work was
actually performed. Fig. 6.7 is the as-built diagram for the West Street
Bridge project. Once the as-built has been prepared, the analysis can proceed. As the as-built diagram (Fig. 6.7) shows, the mobilization activity
started on schedule (the first day of Week 1) and finished on schedule (by
the end of Week 2). The remaining activities, however, did not proceed
in the same manner as the as-planned schedule had predicted.
As the as-built diagram (Fig. 6.7) shows, the pile driving at Piers #1,
#2, and #3; the pile caps at Piers #1 and #2; and Pier Column #1 were
accomplished as-planned in 3 weeks immediately following the mobilization activity. However, the clear and grub activity did not proceed as
planned, but started 2 weeks late and finished in the 1-week planned
duration. If the previous conclusions concerning the critical path were
correct, the delay to the start of clearing and grubbing should not have
resulted in a delay to the project. To check this conclusion, the analyst
can “update” the bar chart as of the end of Week 5, as shown in Fig. 6.8.
As can be seen in Fig. 6.8, the project is still on schedule, but the
abutment and approach work has been delayed, or “pushed out” in time,

because of the delay to the clear and grub activity. As expected, there is
no delay to the critical path. The adjusted schedule (Fig. 6.8) shows the
as-built condition for the first 5 weeks of the project and the adjusted asplanned activities for the remainder of the work.


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Figure 6.7 As-built diagram.

Based on the as-built information, the analyst decides to update the
schedule as of the end of Week 11. The as-built diagram (Fig. 6.7) shows
that the abutment and approach work has not yet begun and that the pier
cap work also has not yet begun. Pier Columns #1 and #2 were completed on schedule. Pier Column #3, however, took 1 week longer to
complete than planned. The adjusted schedule for Week 11 is shown in
Fig. 6.9.


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Figure 6.8 Week 5 update, no delay.

Based on the updated and adjusted schedule presented in Fig. 6.9, the
analyst concludes that the project is now 5 weeks behind schedule. The
delay was caused by the late start of Pier Cap #1 work, which was
planned to start at the beginning of Week 7, but actually started at the
beginning of Week 12. Although Pier Column #3 was late in finishing and

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Figure 6.9 Week 11 update, 5-week project delay.

was on the original critical path, once the Pier Cap #1 activity did not start
on time, the critical path shifted solely to the pier cap work. Pier Column
#3 activity was effectively given float by this shift in the critical path.
Next, the analyst decides to update the schedule at the end of Week
15. This point is chosen because the activities along the bridge pier and


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deck path continued in accordance with the adjusted schedule, but the
abutment and approach work did not. By tracking the two activities that
are precedent to punchlist, specifically the curbs and sidewalks of Span
#4, which are currently driving the punchlist activity, and the paving of
Approach #2, it appears that the critical path shifts in the middle of Week
15. The schedule updated for the end of Week 15 is shown in Fig. 6.10.

Figure 6.10 Week 15 update, no additional project delay.


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As shown in Fig. 6.10, from the end of Week 11 to the end of Week
15, there was no additional delay, despite the fact that the abutment and
approach work continued to be delayed.
To test the previous observation that the critical path shifts in the middle of Week 15, the analyst updates the schedule at the end of Week 16.
The schedule updated for the end of Week 16 is shown in Fig. 6.11.
As can be determined from Fig. 6.11, for the first half of Week 16,
the bridge pier and deck path continued to be the driving activity of the
punchlist work, while the abutment and approach path continued to consume its last half-week of float. Because the pier cap work was progressing
as planned, there was no additional delay for the first half of the week.
Then, the abutment and approach work path became longer than the
bridge pier and deck path and, as the longest path, the abutment and
approach work became critical. Because this path of work continued to
be delayed for the remainder of Week 16, by the end of the week, the
project had been delayed an additional half-week. As a result, by the end
of Week 16, the project had been delayed a total of 5.5 weeks.
Next, the analyst decides to update the schedule at the end of Week
18. This point is chosen because the as-built schedule indicates that the
abutment and approach work actually started at this time. The schedule
updated for the end of Week 18 is shown in Fig. 6.12.
Because the project had been delayed 5.5 weeks as of the last update,
the additional delay since that update is 2 weeks. The activities on the
bridge pier and deck path were not delayed further since the last update.
Instead, the additional 2-week delay was the result of the continued lack
of progress on the abutment and approach path.
Next, the analyst decides to update the schedule at the end of Week
31, which is the time that the as-built schedule shows that the project
actually completed. The schedule updated for the end of Week 31 is

shown in Fig. 6.13.
As shown in Fig. 6.13, no additional delay was experienced during
the completion of the project. At the completion of the analysis, all project delays have been identified. As a final check, the analyst ensures that
the total net delay identified during the analysis equals the number of
days that the project was completed late.
This example follows the conceptual approach to analyzing delays outlined in Chapter 5, Measuring Delays—The Basics. The exact method
used to perform an analysis and the accuracy of the results depend on the
level of detail of the as-planned schedule and of the available as-built
information.


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Figure 6.11 Week 16 update, additional 5-week project delay.

EXAMPLE DELAY ANALYSIS OF POTENTIAL CHANGES
WITH BAR CHARTS
To further illustrate the process of determining delays with a bar
chart, the following example of the construction of a simple, three-story


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Figure 6.12 Week 18 update, additional 2-week project delay.

building is used. Fig. 6.14 is a bar chart schedule for the project. The

critical path is indicated by the red (dark gray in print versions) bars.
During the project, there were four changes that occurred. The analyst has been asked to analyze each of these and determine what delay, if
any, each caused to the project completion date. To perform the analysis,


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Figure 6.13 Week 31 update, total project delay of 7.5 weeks.

the analyst prepared an as-built diagram based on the project daily reports
and other contemporaneous information. The as-built diagram, with the
changed work highlighted in yellow (white in print versions), is shown in
Fig. 6.15.
The analyst, having read this book, understands that the delay cannot be determined simply by comparing the as-planned schedule and


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Figure 6.14 Example 2 as-planned schedule with critical path.

the as-built diagram. Instead, to measure the potential delays caused by
each change, the analyst must apply the changes as they occur.
Alternatively, the analyst could be performing the analysis contemporaneously as the project progresses. In this case, the as-built diagram
would be prepared up to the date of the change and any delays determined at that time.
Fig. 6.16 shows the project through time period 4.5. The actual progress is plotted in green (light gray in print versions), the change in yellow
(white in print versions), and the remaining work in red (dark gray

in print versions) and blue (black in print versions) bars, similar to the
as-planned schedule.


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Figure 6.15 Example 2 as-built diagram with changed work.

As can be seen from a comparison of the as-planned schedule,
Fig. 6.14, and the updated schedule with the changed work, Fig. 6.16,
the project is still scheduled to finish at the end of time period 26.
Therefore, no delay was caused by Change #1.
The next change to the project occurs during time period 6. The
analyst has updated the bar chart through time period 6.5, as shown in
Fig. 6.17, with the actual progress in green (light gray in print versions), the changed work in yellow (white in print versions), and the
future work in red (dark gray in print versions) and blue (black in print
versions) bars. As can be seen from a comparison of the first update of


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Figure 6.16 Time period 4.5 update.

the schedule, Fig. 6.16, and the present update of the schedule,
Fig. 6.17, the project has been delayed one-half time period and will
now finish in the middle of time period 27. It is also noted that

Change #2 affected the critical work of the underground utilities. As a
result of these observations, the analyst can conclude that a delay has
occurred because of Change #2 and that the delay is one-half time
period in duration.
The next change to the project, Change #3, occurred during time
period 14. The analyst has updated the bar chart through time period 14
to include the changed work. This is shown in Fig. 6.18, with the actual


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Figure 6.17 Time period 6.5 update.

progress in green (light gray in print versions), the changed work in yellow (white in print versions), and the future work in red (dark gray in
print versions) and blue (black in print versions) bars. As can be seen
from a comparison of the preceding update and this update, the end date
of the project has not changed; therefore, Change #3 did not affect the
critical path, and no project delay resulted.
The next change, Change #4, occurred during time periods 15
through 17. The analyst has updated the bar chart schedule through
time period 17 to include the changed work. This is shown in
Fig. 6.19, with the actual progress in green (light gray in print


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Figure 6.18 Time period 14 update.

versions), the changed work in yellow (white in print versions), and the
future work in red (dark gray in print versions) and blue (black in print
versions) bars. Comparing this update with the preceding update shows
that the project end date has moved to a later date. The project will
now complete at the end of time period 27 and has been delayed an
additional one-half time period. Note that the critical path has changed. Because of the duration of the changed work, a path that previously had float is now the critical path and caused the delay that was
measured.


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Figure 6.19 Time period 17 update.

This simple example demonstrates how a bar chart can be updated
contemporaneously to determine the effect of changes while the project
progresses or after the project work is complete.