Six-sigma as a strategy for process improvement on
construction projects: a case study
RODNEY A. STEWART1* and CLINTON A. SPENCER2
1School of Engineering, Griffith University Gold Coast Campus, PMB 50 Gold Coast Mail Centre QLD 9726,
Australia
2GHD Consulting Engineers, GPO Box 668, Brisbane QLD 4001, Australia
Received 21 July 2004; accepted 10 June 2005
Significant expenditures of time, money and resources, both human and material, are wasted each year as a
result of inefficient or non-existent quality management procedures. In an attempt to improve their market
competitiveness, by limiting the extent of non-value-adding activities, some organizations are beginning to
monitor the performance of internal and external engineering and construction processes. To achieve these
bold aims, these organizations are looking to other industries such as manufacturing to examine the
effectiveness of measuring and monitoring tools such as six-sigma. Only in recent years has the six-sigma
method been utilized by some of the major players in the construction sector. To familiarize both researchers
and practitioners on how to implement the six-sigma method and its potential benefits, the paper describes the
outcomes of a six-sigma process improvement project (PIP) conducted for the construction of concrete
longitudinal beams on the St Pancras raised railway station in London, UK. The outcome of the six-sigma PIP
was the improved productivity of beam construction, enhanced interaction between project teams and reduced
project delays. Moreover, interviews with key project participants were conducted to determine the success
factors, barriers, suitability and advantages of the six-sigma approach compared with other TQM techniqes. In
summary, the six-sigma approach provided the PIP team with a structured process improvement strategy to
reduce waste and other non-value adding activities from the construction process.
Keywords: Six-sigma, process improvement, total quality management
Introduction
The construction industry is a business sector that plays
a substantial role in many economies. However, the
attainment of acceptable levels of quality in the
construction industry has long been a problem.
Significant quantities of resources, both human and
material, are wasted each year as a result of inefficient
or non-existent quality management procedures (Arditi
and Gunaydin, 1997). There exists great potential for
quality improvements in the construction industry; its
importance cannot be understated, regardless of a
nation’s primary business, and organizations will
always require interaction with the construction industry to source physical assets to house operations (Cox
and Ireland, 2002). In recent years, globalization and
deregulation of markets has led to increased foreign
participation in domestic construction, placing further
pressure on leading firms for major reforms. The cause
of many problems lies in the organization of the
industry and associated processes. Firms need to build
on their competitive strengths through a deliberate and
managed process to improve the capacity and effectiveness of the industry and to support sustained
national economic and social objectives.
This study suggests that this development, in part,
can be achieved by learning how to increase efficiency
and productivity through process improvement. As a
small step towards achieving this goal, we firstly present
a review of a wide variety of existing process improvement techniques and then critically evaluate the use of
six-sigma in other industries with a view to demonstrating how the phenomenon can be used as a strategy
*Author for correspondence. E-mail: [email protected] for construction firms. Six-sigma is a structured
Construction Management and Economics (April 2006) 24, 339–348
Construction Management and Economics
ISSN 0144-6193 print/ISSN 1466-433X online # 2006 Taylor & Francis
http://www.tandf.co.uk/journals
DOI: 10.1080/01446190500521082
methodology that has found wide acceptance in the
manufacturing sector by such firms as General Electric
and Motorola. In essence, the principles of six-sigma
have been derived from total quality management
(TQM) theory. However, its structured and systematic
framework, combined with the employment of statistical techniques, makes it an excellent tool for process
diagnostics, which is an integral task of modern
construction managers. The methodology has led to
significant improvements in the manufacturing sector
and it is believed that it should also assist construction
firms to deliver projects on time, at the right cost and of
superior quality (Wantanakorn et al., 1999). Secondly,
this article demonstrates the application of six-sigma in
an industry-based case study to illustrate its usefulness
in a complex site environment. Lastly, interviews with
key project participants were conducted to extract sixsigma learning experiences and to determine the
effectiveness of the method for achieving process
improvement in the construction sector.
Process improvement in construction
The aim of process improvement in construction is to
produce something of equal or better worth, at a lower
cost. Brown and Adams (2000) reported that in the
procurement of projects, leading clients are increasingly
demanding a high quality product at a low cost, which
is also reliable and delivered on the date required. The
major feature of construction processes is that they are
notorious for their complexity and changes during the
construction process (Van der Aalst et al., 2002). The
industry has few structured frameworks on which to
base process improvement initiatives and achieve total
quality. The absence of clear guidelines has meant that
improvements are often isolated and benefits cannot be
coordinated or repeated. Sarshar et al. (2000) attribute
this to the industry’s inability to assess construction
processes, prioritize process improvements and direct
resources appropriately. Subsequently, the concept of
process improvement varies for construction firms,
unlike in manufacturing, where variation can be
eliminated because the standards by which it is
measured are themselves invariant – e.g. production
lines. In construction, clients inevitably have variability
in their requirements; consequently variation cannot be
totally eliminated, but it can be managed (ShammasToma et al., 1998). In recent years, a number of
structured performance improvement methods have
been adopted on construction projects. However, their
degree of success has been somewhat less than that
experienced in manufacturing industry. The following
paragraphs provide a critical review of these models and
examine their fitness-for-purpose for the construction
sector.
A number of techniques and tools can be found
under the TQM/Continuous Process Improvement
(CPI) umbrella, including the process cost model,
standardized process improvement for construction
organizations, the balanced scorecard, Kaizen and
statistical process control. Traditionally, businesses
have tended to measure performance using only
financial measures. As a result, organizations adopted
techniques similar to the process cost model (PCM).
This concept was developed in manufacturing industry
and has been moulded into a workable strategy suitable
to construction applications (Aoieong et al., 2001). The
PCM is a process-orientated approach that values
client satisfaction and continuous process improvement. PCM uses financial theory to analyse and direct
efforts for improvement; this has its advantages and
disadvantages. Use of a single measure clearly illustrates the tangible benefits in a compatible format that
is easy to interpret (Arditi and Gunaydin, 1997; Moen,
1998). However, the weakness of financial metrics
stems from their failure to measure and monitor
multiple dimensions of performance. Additionally,
financial measures used in isolation create problems
in that they are characterized as lagging measures, i.e.
they are the result of past events. Consequently, PCM
is a reactive approach, because waste and associated
non-value adding activities have already transpired. For
construction firms to succeed in the future they need to
implement a more proactive approach to improving
processes (Moen, 1998).
To look beyond financial measures, Sarshar et al.
(2000) developed the standardized process improvement for construction enterprises (SPICE) framework.
This framework was founded on the principles of
the capability maturity model (CMM) and argues that
the outcome of a process is a function of the maturity
of the organization and its associated processes
(Hutchinson and Finnemore, 1999; Sarshar et al.,
2000). The philosophy of this framework is that a
process becomes more predictable and reliable as the
organization and its processes simultaneously mature.
SPICE provides a structured framework with a definite
starting point that assists the process improvement
teams to prioritize areas for improvement. The SPICE
framework provides a good process diagnostics tool
with a strong process focus. Sarshar et al. (2000)
demonstrated the application of the SPICE framework
in two case studies aimed at improving construction
processes. An interesting outcome of these studies was
that an organization does not have the capability to
capture best practices until ‘level 3 (defined)’ of the
framework. In light of this, the SPICE framework has
340 Stewart and Spencer
many similarities with six-sigma, particularly in its
ability to address priority processes.
Although the two previous techniques provide an
indication as to the success or failure of a project, they
do not provide a balanced view of a project’s
performance. Kaplan and Norton (1992) developed
the balanced scorecard (BSC) to capture both the
tangible and intangible perspectives of performance.
The BSC provides information on four perspectives,
including customer perspective, internal business perspective, learning and growth perspective and financial
perspective. However, this approach is far from simple
and requires a comprehensive understanding of the
fundamental characteristics of performance measurement as well as a significant commitment from top
management and employees (Chan et al., 2002).
Moreover, construction firms may find implementation
difficult due to the diversity of their projects
(Sommerville and Robertson, 2000). Hubbard (2000)
also felt that the BSC was too generic in design and did
not consider a specific industry’s needs or the strategic
desires of individual organizations.
Another process improvement technique that was
developed by the Japanese and was a contributor to
their economy’s rapid growth in the second half of the
twentieth century was Kaizen. This technique was
formed from a quality culture that emphasizes continuous process improvement through standardization
– i.e. establish a standard, maintain it and then improve
it (McGeorge and Palmer, 2002). However, the
technique tends to be difficult to adopt for firms that
have already implemented the TQM culture. In view of
this, the authors do not believe that Kaizen can offer the
construction industry substantial benefits since it
merely promotes similar ideals already created through
TQM. What the industry needs is a structured datadriven approach to direct its efforts.
A more data-driven technique is statistical process
control (SPC), which has an emphasis on numbers,
fact-based analysis and tangible decision-making.
Consequently, due to its technical nature, it has never
been fully embraced (Dale et al., 2000). With managements becoming more interested in performance and
profitability, they are beginning to divert attention back
to the analysis of process variation and elimination
through root cause analysis and problem solving. Use
of SPC identifies overall process capabilities and areas
that need improvement. Although SPC equips the
users with an extensive array of measurement techniques it appears to lack a strong organizational
supportive framework. The tools employed by
SPC have, to a large extent, fuelled the development of the latest addition to the TQM/CPI umbrella:
six-sigma.
Six-sigma in construction
Six-sigma is a new way of managing business processes.
Since its publicized adoption at Motorola and General
Electric in the early 1980s, six-sigma has evolved into a
leading method for managing process efficiency, not
just in manufacturing industry but increasingly in other
areas close to project managements’ ‘heart’ such as
construction management. It is a formal and disciplined method for defining, measuring, analysing,
improving and controlling (DMAIC) processes (see
Figure 1). These five steps form the backbone of the
six-sigma methodology and work on the principle of a
stage/gate process that requires certain deliverables to
be met at the gate before the firm can proceed to the
next stage or phase (Marves, 2000). While traditional
quality programmes have focused on detecting and
correcting mistakes, six-sigma encompasses something
broader: it provides specific methods to re-create the
process itself so that the defects are never produced in
the first place. The concept seeks to continually reduce
variation in processes with the aim of eliminating
defects from every transaction (Hahn et al., 1999;
Tennant, 2001). Antony and Banuelas (2002) define
six-sigma from both a business and statistical perspective.
From a business perspective, they describe six-sigma as a
strategy used to improve profitability, reduce quality
costs and improve overall operations to exceed the
customer’s expectations. In a statistical vocabulary, sixsigma refers to 3.4 defects per million opportunities
(DPMO), where sigma represents the variation about
the process average. Six-sigma executioners progress to
become qualified experts, trained in six-sigma philosophy and methodology, and are referred to as ‘black
belts’. As process improvement project (PIP) leaders
these experts carry in-depth knowledge of techniques
such as process mapping, measurement analysis,
analysis of variance, supply chain management and so
on.
Six-sigma has different interpretations and definitions for different applications; in this case we refer to
its proposed application to the construction/engineering sector. For this sector, six-sigma improvement
methods are not about being totally defect-free or
having all processes and products at six-sigma levels of
performance – another misconception of the six-sigma
philosophy (Linderman et al., 2003). The appropriate
level will depend on the strategic importance of the
process and the cost of its improvement relative to the
benefit (Brue, 2002). In the application of six-sigma
there are typically a number of common features, which
include: it is a top-down rather than bottom-up
approach; it is a highly disciplined approach that
typically includes five stages (i.e. DMAIC); and it is a
Six-sigma as a strategy for process improvement 341
data-oriented approach using various statistical and
non-statistical decision tools (Klefsjo et al., 2001).
This use of a structured approach to improving
processes in construction helps to reduce task complexity
while increasing performance and commitment from
team members (Linderman et al., 2003). The DMAIC
methodology simplifies the process improvement project
because it acts like a road map for the improvement
team. In the manufacturing industry, six-sigma has
typically been applied in an organization-wide manner,
choosing macro opportunities as six-sigma projects.
Consequently, in manufacturing, we have tended to
witness revolutionary changes. These projects have
tended to involve the design and development of an
entirely new product or service or the major redesign of
an existing one. Conversely, at this stage, the deployment
of six-sigma in the construction industry has been
predominately aimed at micro-opportunities. This means
that six-sigma projects would be smaller in scope and
likely to relate to a sub-task within a macro opportunity.
Keeping with the philosophy of CPI and TQM, the
application of six-sigma at this early stage of its
development is to argue enhancements for evolutionary
rather than revolutionary changes (Maleyeff and
Kaminsky, 2002). Applying six-sigma in construction
typically involves breaking down large tasks into smaller
ones that can be re-engineered and improved. The
main advantage of the six-sigma method is that it shares
much of the same values and uses similar tools to TQM.
The tools are nothing new, but the strategic way that
the six-sigma programme proactively uses them, within
its structured framework, is what generates improved
results. Like TQM, six-sigma is a people-focused
management system that aims to continually increase
customer satisfaction by reducing real costs through a
reduction in variation and causes of poor quality
(Klefsjo et al., 2001). It works by involving all employees, top-to-bottom, as a structured team. In order to
efficiently use statistical tools to base decisions on fact,
substantial effort is required to train employees. In
doing so, authority is allocated through a ‘karate belt’
system, creating a comprehensive infrastructure of
resources to achieve quality and process improvements.
Team members are equipped with knowledge of sixsigma and, most importantly, the processes that they
are analysing. In this manner six-sigma emphasizes the
involvement of people who carry out the processes on a
daily basis. For construction organizations this promotes the collection of data from a level close to the
data source. Moreover, the participation of process
owners is essential to ensure that the process improvement teams formulate more creative and practical
responses.
Case study
The purpose of this case study was to demonstrate the
potential of six-sigma to achieve CPI in construction
and to highlight the benefits of introducing a structured
assembly-line doctrine to construction processes. The
case study was based on a PIP for a contract in the
United Kingdom. The contract, Contract 105 (C105)
of the Channel Tunnel Rail Link (CTRL) includes the
construction of an extension to the existing St Pancras
Station, London. The contract for construction
included participants from the following companies:
Costain, O’Rouke, Bechey and Emcor Rail
(CORBER). Following completion, this station will
become the main London terminal for international rail
passengers using the Eurostar service in 2007. The
platform extension was built in two halves, the east and
west deck. This paper examines the construction of the
east deck, which comprises the following major civil
engineering activities: diversion of underground services (utilities); demolition of existing road and rail
infrastructure; construction of piles, pile caps and
Figure 1 Six-sigma’s structured methodology – DMAIC
(adopted from Brue, 2002)
342 Stewart and Spencer
columns to support the station extension platforms;
and construction of beams that will comprise the new
station platforms and tracks.
This research project was conducted to achieve two
primary objectives: (1) describe the application of the
six-sigma method on a construction project; and (2)
evaluate the effectiveness of this method for achieving
CPI in the construction sector. The research method
adopted to achieve these objectives consisted of two
parts. Firstly, the decisions made and their outcomes
for two PIPs were recorded under the five stages
of the six-sigma philosophy – define, measure, analyse,
improve and control. Secondly, six of the PIP team
members (i.e. six-sigma black belt consultant, site
engineer, site foreman, design manager, construction
coordinator and station extension manager) were
interviewed to determine their perceptions of the
barriers, critical success factors and suitability of sixsigma in the construction sector. Additionally, the
interviewees were requested to comment on the
advantages and disadvantages of six-sigma compared
to other TQM techniques. It should be noted here that
the researchers did not attempt to formulate a
construction-specific framework due to the limited
number of participants who have had experience using
the six-sigma methodology. However, the described
DMAIC steps and learning experiences documented
from this project should be useful for future researchers
and practitioners attempting such a task.
Define
This six-sigma PIP was initiated to improve the
construction of raised platform beams with the explicit
aim of identifying particular activities that were causing
defects. A defect in terms of this process relates to the
late delivery of platform beams, i.e. in comparison to
the construction programme. The main features of the
platform construction include piles, pile caps, support
columns, pre-cast T-beams and platform beams.
Evidently, the construction of the platform beams was
dependent on a number of other activities that
subsequently had the potential to impede their progress. The business case for this PIP was built around
the additional cost incurred to the project due to delays
in the construction of the platform beams. The cost of
poor quality (COPQ) associated with delays caused by
the beams include the following: (1) the cost (above
budget) of additional equipment and labour required to
accelerate the construction (i.e. crash the project) to
meet the programme; (2) the cost of maintaining
equipment and labour on site beyond the planned
completion to work off the deficit; (3) the impact of the
above two factors on follow-on activities such as roof
construction and fit-out; and (4) the £54k per day
penalty for delay to opening the interim station.
A comparison between the scheduled and the actual
beam construction performance is illustrated in
Figure 2. At this early stage of the project only 32 of
the 276 beams were completed; the figure illustrates
that there was plenty of room for improvement for the
remaining beams. A review of past performance
revealed that the rate of beam production was 2.3
beams per week, whereas the target was 2.9 beams per
week. If this performance continued, the construction
of the beams for the interim station (146 beams) would
overrun by 8 weeks (Figure 2). The average weekly cost
(labour, equipment and materials) of the beams is
£71k. An eight-week overrun of labour pay and
equipment hire would cost an additional £0.57k. In
addition, liquidated damages (LDs) of £54k per day
are levied for the delayed opening of the station. If the
delay to the beams directly impacted the opening of the
station, the LDs would amount to £3.02M.
The goal of the PIP was to reduce the delays to the
beam operation, reducing the forecast delay by four
weeks, saving £284k (i.e. half of £0.57k) of labour and
equipment costs. The team attempted to reduce the
time taken to construct platform beams and improve
the handover process by either increasing work
efficiency or by reducing factors leading to delays.
The primary metric was the gap in the beam
performance (number planned to date versus number
actual to date) measured on a weekly basis. The
secondary metric was the gap in the cost performance
(the difference in the planned and actual cost to date).
This metric was monitored to highlight whether
increased performance was due to excessive resources
being deployed.
Figure 2 Beam performance gap analysis – east deck
extension
Six-sigma as a strategy for process improvement 343
Measure and analyze
In this phase of the beam construction process the team
initially took a broad project-wide approach when
searching for potential problem areas and associated
measures in pre-beam activities. A cause-and-effect
analysis (i.e. mapping the beam construction process
and examining the impact of different scenarios and/or
production rates on the process’s efficiency) was
carried out with the process owners to establish the
more general causes (i.e. pre-beam activities) of delays
to the beam construction process. The feedback from
this exercise was that some preceding construction
activities were causing delays to the beams. The
exercise was expanded to include the managers of the
other activities that precede the beam construction
process. It became very clear from the cause-and-effect
analysis that the success of the beams was heavily
reliant on preceding activities such as site access,
utilities and road diversions, demolition, piling, pile
caps, and columns.
The beam construction process necessitated a heavy
reliance on multiple interconnected activities. The
coordination of these activities and the interface
between them played a considerable part in the
eventual success of the on-time delivery of the beams.
Discussions with members of the team in an informal
workshop revealed several instances where poor coordination had caused significant delays/cost overruns to
the beams or preceding processes. Many of these issues
were attributed to the lack of a formal handover
between three project teams: (1) utilities; (2) demolition and piling; and (3) deck team (pile caps, columns
and beams). This was due to the fact that the teams
were working independently and were not considering
the needs of their customers. This individualistic
culture evolved from the way in which the teams were
measured. Progress charts were produced on a weekly
basis and issued to the project participants and the head
office. However, these charts served as individual team
motivators rather than common goal drivers. For
example, the piling team were recognized for placing
concrete in the ground, not for delivering a satisfactory
pile to the pile cap team, once the testing had been
successful. It all comes back to the fundamentals of
goal theory and motivating everyone collectively to a
common goal. The PIP team realized that they needed
to motivate workers to take ownership of what they do,
through emphasizing the importance and contribution
of their task to the overall success of the project. The
departmentalization of the project, in effect, led to
counterproductive fragmentation in the overall scheme
of the project. Only after the process improvement
team had participated in several weekly progress
meetings did they realize the need for a coordinated
programme so that progress and productivity projections would be discussed in terms of the whole project.
The main outcome of this review was the creation of a
second separate PIP (i.e. PIP2). The main focus of
PIP2 was to guarantee the effective coordination of the
activities associated with the construction of the beams
and their interface with the piling and pile cap teams.
Together these activities were considered as a significant contributor to the delay of the platform beam
construction.
The findings of the second PIP suggested the
creation of a coordinated plan linking piles, pile caps,
columns and beams. This schedule would link all the
major activities, showing which columns were needed
for each pair of beams, which pile caps were needed for
the columns and which piles were needed to support
the pile caps. This scheduling method allowed construction durations to be known; thus target dates for
piles, caps and columns could be listed. The main
advantage of this method was that the impact of lastminute changes or drops in performance by one team
could be assessed by others (process owners).
A technique used to help gather data to further
measure the construction process was the constructability workshop. The attendees included designers,
site agents, construction managers, foreman and
architects as well as the members of the process
improvement team. The aim of these sessions was to
review the construction process and to gain an insight
on any problems occurring in the process. The PIP
team’s next task was to sit down with the appropriate
lead departments to have these issues rectified and
most importantly communicated back to the site
operatives so that improvements could be made.
Following a further review of the effects of the
problems identified during the constructability workshop, it was decided to collect data on the duration of
beam construction. The team’s objective was to
establish a theoretical performance for the construction
of a single platform beam (beams were poured in 15m
lengths). The start, end time and date were recorded by
the beam field engineer on a data collection sheet. This
information was then entered into a workbook so that
performance could be measured and monitored to
identify what processes were causing delays.
Production schedules (i.e. mapping the beam construction process) for the platform beams for the next
12 pours were created. The schedule illustrated how
the equipment progressed on three overlapping fronts
using three sets of falsework (including tables), yet only
one set of formwork. An assessment of the equipment
requirements for the remainder of the east deck was
carried out. This analysis illustrated that at current
resource levels (three sets of falsework legs and a single
set of steel formwork) the programme targets could not
344 Stewart and Spencer
possibly be met. Additionally, the entire construction
programme was at risk should damage occur to this
critical equipment. If these current levels of equipment
were maintained it was estimated that a two-month
delay would occur. Following this estimate an analysis
was made of the appropriate levels of equipment
(formwork and falsework) needed to meet the contract
programme. The analysis used the latest revision of the
construction programme (following the completion of
PIP2) to show how the amount of formwork and
falsework used would affect theoretical production
rates. Figure 3 details the relationship between equipment levels and theoretical production rates. This
figure illustrates that an additional set of falsework
(tables) and an additional set of formwork were
required to reduce the revised programme by four
weeks. This analysis also demonstrated that there was
diminishing return from the procurement of further
additional equipment.
Improve
The previous phases drew the PIP team’s attention to
three areas relating to the construction of platform
beams where improvements could be made and
subsequent time/cost savings realized. These areas of
improvements included: (1) pre-beam activities; (2)
efficiency of beam construction based on the duration
of construction; and (3) equipment levels (i.e. formwork). The first area of improvement related to the
pre-beam activities. The process improvement team
initially reviewed the pre-beam activities (i.e. ground
works, piles and pile caps). The PIP team discovered
that these activities required efficiency-related improvements. Subsequently, the team constructed a coordinated programme which allowed project teams to
discuss productivity projections in terms of the whole
project. This was achieved by formulating a schedule
linking all the major activities supporting the beam
construction. This outcome was achieved through a
separate PIP working in parallel (i.e. PIP2); this PIP
provided enhancements to the on-time delivery of
beams by minimizing the impact of pre-beam activities.
The second area of improvement targeted gaps in the
construction process. During meetings, the PIP team
stressed the importance of formal communication
channels between department heads and foremen
(including general site operatives) to ensure that when
future problems were identified, they could be remedied efficiently and effectively. Finally, an analysis on
the current levels of equipment used was conducted
and it was recommended to purchase an additional set
of falsework (tables) and formwork.
Control
Several members from the PIP team were responsible
for ensuring that the schedule of action items (identified in constructability workshops) and associated
action parties (departments) sustained the improvement(s) that had been achieved. Moreover, this select
group were allocated the role of monitoring the
performance of this process. Their role was to maintain
close supervision and training of operatives to achieve
further improvements. To sustain improvements, the
PIP team monitored the construction of the beams with
the charts developed in the measure and analysis phases
of the improvement process. A review of these charts
indicated that there had been noticeable improvements
in most of the activities – specifically, less variability in
activity durations. To illustrate this reduction in
variability, Figure 4 details the total time to complete
the beam construction. Theoretically, it was recommended that a 15m length of platform beam should be
Figure 3 Comparison of equipment levels Figure 4 Control/monitoring chart for beam construction
Six-sigma as a strategy for process improvement 345
completed in 8.5 days allowing for small abnormalities.
Figure 4 highlights that the process is improving, and is
continually being perfected. The control charts allowed
the PIP team to identify problems with the potential to
cause significant delays to timely project completion.
Summary
The primary outcome of the study was a number of
contributions to the planning and management of the
beam construction process. The PIP discovered that
the major source of delays resulted from preceding
activities and current equipment levels. Over the
duration of the project, beam production performance
has improved substantially (Figure 4). This has mainly
resulted from the timely completion of service relocations. Moreover, an increase in efficiency resulted from
the development of a coordinated construction programme that reduced the amount of piecemeal
construction. The major findings and recommendations from this case study are as follows: (1) the most
significant factor influencing the performance of beam
construction is the availability of the site; (2) coordination of the construction activities through the use of
monitoring and projection tools enabled the teams to
work together, rather than independently; (3) continued collection of performance data (i.e. control phase)
helped to highlight areas where future process improvements could be made; and (4) project teams should be
measured in a different way, whereby they were
rewarded for the handover of a defect-free structure
to the next team.
Evaluation
To evaluate the effectiveness of the six-sigma method, a
small number of interviews (N56) were conducted
with some key project participants. These interviews
sought to ascertain respondents’ perceptions as to the
success factors, barriers and suitability of the six-sigma
method for improving the performance of construction
processes. Moreover, the interviewees were requested
to compare the six-sigma approach to other TQM
techniques. Most of the interviewees identified management commitment, appropriate organizational
infrastructure and linking six-sigma to business strategies as the critical success factors for achieving effective
six-sigma implementation. Surprisingly, the interviewees identified the selection of an appropriate PIP as
the most significant barrier. Other barriers identified
included resistance from workers, implementing
required changes and a lack of understanding of
the six-sigma approach. Clearly, there are also
other barriers to overcome to ensure the success of
six-sigma. The ability of the organization to proactively
acknowledge further barriers will increase their likelihood of delivering sustainable improvements to
construction processes. The interviewees were questioned as to whether they believed six-sigma was a
suitable method for improving quality and efficiency in
the construction industry. All the respondents agreed
that six-sigma was well suited to the industry provided
that the PIP could be clearly defined as a series of
processes and that senior management introduced the
method in a supportive manner. One interviewee
commented: ‘this technique is well structured and
lends itself to many processes within construction’.
Interestingly, the interviewees perceived that six-sigma
mainly improved efficiency but not quality. They
thought that the main improvements were in the areas
of coordination, process planning and cost allocation.
However, these comments only demonstrate that many
construction professionals have a common misconception about the concept of ‘quality’ and its relationship
to the whole procurement process. This misconception
is best described by one of the respondents who
commented that ‘improved efficiency5less panic5better product’. The interviewees were asked whether they
thought that six-sigma should be applied to future
construction projects. They predominately indicated
that as long as six-sigma was applied by an experienced
management team it had potential to refine processes
and ultimately enhance the bottom line.
Lastly, the interviewees were requested to compare
the six-sigma approach to other TQM approaches they
had adopted previously. Most of the interviewees found
that six-sigma was more statistically oriented and better
structured for overcoming construction problems.
They generally considered that six-sigma was best
applied for well-defined problems and for process
diagnostic solutions. None of the interviewees confirmed that one approach was better than another.
Their overall consensus was that the six-sigma method
was better for getting to the heart of an isolated or a
complex process problem quickly and efficiently. TQM
on the other hand, was considered to be better for
system-wide organizational improvement and deployment.
Conclusion
The structured yet flexible six-sigma framework provides a solid procedure for the gathering of information
on the sequence of construction processes, enabling
process and quality improvements. Misconceptions of
six-sigma method stem from its origins as a manufacturing approach; however, six-sigma also has the
potential to improve processes in construction. The
346 Stewart and Spencer
main advantage of six-sigma is that it uses its people to
reach a practical solution – it doesn’t just attempt to
revolutionize construction procedures with mechanized
process improvements.
Despite the large number of studies having addressed
the concept of quality in construction, there is limited
research into the use of six-sigma as a strategy for
process improvement in construction. In an attempt to
address this gap in the research, this article has
presented a review of six-sigma and its subsequent
application in an industry case study. The case study
described the outcomes of a six-sigma PIP conducted
for the construction of concrete longitudinal beams in
the St Pancras raised railway station in London. The
outcome of the six-sigma PIP was the improved
productivity of beam construction, enhanced interaction between project teams and reduced project delays.
The literature and associated case study detailed
herein provides essential implications for both researchers and practitioners. Firstly, it provides a solid
foundation for academics to enhance the six-sigma
process improvement methodology for the benefit of
future construction and engineering projects. Secondly,
practitioners interested in improving their own project
productivity can utilize the explanations, outcomes and
learning experiences detailed in the above-mentioned
case study to enhance their productivity, reduce delays
and maximize profitability on projects.
Due to the limited application of six-sigma in the
construction industry, this research principally sought to
document its implementation in an industry-based case
study and examine the benefits derived. Future research
should quantitatively compare the benefits derived from
a six-sigma approach to other popular CPI techniques
and tools. Moreover, academics and practitioners
should attempt to formulate industry-specific guidelines
for six-sigma implementation, not only for the larger
enterprises but also the small and medium ones.
Furthermore, researchers should attempt to evaluate
the impact of partnering on the six-sigma approach and
develop means for six-sigma to be fully integrated into
the entire construction supply chain.
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