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Time Waste in Construction Process

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Abstract

Time Waste is Different from Delays. Graphical representation is shown
TIME WASTE IN CONSTRUCTION PROCESS MANAGEMENT.
Safeer Ali Abbas Ali
PhD scholar, National Institute of Technology, Calicut, India.
safeeraliabbas@gmail.com
Arun C
Associate Professor, National Institute of Technology, Calicut, India
arunc77@nitc.ac.in
Abstract: The Oxford English dictionary defines waste as “use or expend carelessly, extravagantly, or to
no purpose”. It was seen from literature that ‘wastes’ and ‘material wastes’ are used interchangeably in
construction sector. Systematic addition of wastages in construction projects occur in a number of
activities, which results in significant time and cost overruns.
Further, literature studies showed that delays in construction sector is a problem worldwide that has not
been sorted out. One of the major causes of delays may be attributed to systematic addition of 'time
wastes' in the various activities involved. Studies pertaining to activity oriented time wastes are not
plentiful. One of the major causes may be attributed to the fact that, time waste is not properly defined.
Further, quantification of time wastes is also not properly done, and a universal unit for measurement of
time waste is not existent.
This paper explores various possible units that can be used to quantify activity oriented time waste. One
of the important units of time wastes is ‘time’. But, it has been seen that there are inconsistencies arising
as a result of making time as a viable option for quantifying time wastes.
It was seen that one of the possible unit would be units of ‘money’. It was seen to be consistent in
measuring wastages uniformly. Both direct and indirect time wastes that occur in construction sites could
be successfully quantified by using this unit. It is proposed as an important tool in further research to
reduce time wastes and in the process, reduce construction delays as well.
Keywords
Time Waste, Waste, Delays, Units of Time waste, Money, Lean Construction
1. Delays & Waste in Construction.
Wastes in construction process occur periodically, thus leading to construction project delays. One of the
serious issues that continually affect the smooth running of construction industry is construction delays.
Many reasons are attributed to the causes of these delays which today, are considered by many, as
unavoidable and almost not eradicatable. Research into causes of these delays is plentiful worldwide and
is seen as a routine area of study. This chapter gives a good insight into delays occurring worldwide. A
few examples quoting the reasons for delay are also come across.
1.1 Causes of Delays - Contractors
One of primary causes of delay has been attributed to contractors. Abd El-Razek et.al (2008) in his
study on the construction sector in Egypt found that delays in completion of projects are primarily caused
by the following: design changes by the owner or his agent during construction, delays in contractors
payment by the owner, partial payments during construction, non utilization of professional
contractual/construction management and financing by contractor during construction. Delays also have
strong relationship with failure and ineffective performance of contractors. Ubaid (1991) discussed the
performance of contractors as one of the major causes of delay. Thirteen major measures were
considered. These measures are related to contractor resources and capabilities. Al-Momani (2000)
investigated causes of delay in 130 public projects in Jordan. The main causes of delay were related to
designer, user changes, weather, site conditions, late deliveries, economic conditions and increase in
quantity. The study suggested that special attention to these factors will help industry practitioners in
minimizing contract disputes.
1.2 Causes of Delays – Improper Planning
Beyond contractors, it is seen that delay is a primary cause due to errors arising from planning stages.
Towhid et al (2011) studied causes of delay in Iranian construction sector and identified 10 most
important causes of delay viz., poor contract management by consultants, poor site management, delay in
progress payment by clients, delay in reviewing and approving design documents by clients, ineffective
planning and scheduling of project by contractor, slowness in decision making by client, delay in
producing design documents, problems with subcontractors, change orders by client during construction
and financial difficulties faced by the contractor.
1.3 Causes of Delays – Improper design
Other primary factor has been attributed to the design phase. Saleh Al Hadi et.al (2009) studied causes of
delay in Libyan construction industry and found 43 factors and responsible for delay. The top three
factors responsible were improper planning, lack of effective communication and design errors. The
study further presented factors as the impact of these delays viz. losing of interest by stakeholders,
blacklisting by authorities, wastage of time and money and declination of reputation.
Study conducted by Faridi & El-Sayegh (2006) on delays for construction projects in Dubai showed that
delays in preparation of drawings and designs as most frequented cause of delays in Dubai. Inadequate
early planning, slowness of the owner’s decision-making process, shortage of man power, poor
supervision & site management, productivity of manpower, skill of manpower, non-availability of
materials on time and obtaining approval from authorities and financing by contractors during
construction were identified as other major causes of delays.
1.4 Causes of Delays – Adverse Site Conditions
In some cases, site conditions are primary factors of delay. Chan et.al. (1997) surveyed and evaluated the
relative importance of 83 potential delay factors in Hong Kong construction projects and found five
principal factors: poor risk management and supervision, unforeseen site conditions, slow decision
making, client-initiated variations, and work variations.
1.5 Causes of Delays – Inflation & Political Reasons
External factors such as inflation have also been seen to cause delays. Kaming et al. (1997) studied
influencing factors on 31 high-rise projects in Indonesia and found out that cost overruns occur more
frequently and are more severe problem than time overruns. The study pointed out that the major factors
influencing cost overrun are material cost increase due to inflation, inaccurate material estimation and
degree of complexity. As for time overruns, the most important factors that cause delays are design
changes, poor labor productivity, inadequate planning, and resource shortages.
At times, political reasons also tend to influence the construction process and leads to delays. Ibrahim
Mahamid et.al (2011) conducted detailed study on delay of road projects in West Bank, Palestine. It
identified 52 causes. They study concluded five severe causes as the political situation in West Bank,
award project to lowest bid price, shortage of equipment, progress payment delay by owner and the
segmentation of west bank and limited movement between areas. Comparative study by Yong et.al (2008)
showed varying causes depending on the area of study (Table 1).
Figure 1. Major Causes of Delay World Wide
2. Waste in Construction
The theoretical aspects of wastes have certain deficiencies when it comes to quantifying type of waste and
its subdivisions. In order to understand these, a deeper know how of waste in general is required, before
venturing into construction wastes.
Wastes usually have different definitions basing on context of purpose. No exact definition has been
found to be in use universally. The Oxford English dictionary defines waste as “use or expend carelessly,
extravagantly, or to no purpose” of any object considered.
BusinessDictionary.com gives a much more detailed explanation for waste, as follows
(A). General Context (Waste):
(1) Resources consumed by inefficient or non-essential activities.
(2) Unwanted material left over from a production process, or output which has no marketable value.
(3) Process or material that does not (from the viewpoint of the customer) add value to a good or service.
(4) Material discharged to, deposited in, or emitted to an environment in such amount or manner that
causes a harmful change.
(B) Lean production (Waste):
Activity that consumes resources but adds no value. Called muda in Japanese, wastes are divided into
seven types:
(1) Over-production: producing something more than the demand, or before it is needed.
(2) Waiting: for the next process step due to long cycle time.
(3) Transport: unnecessary movement of material or parts due to inappropriate location of equipment or
machines.
(4) Over-processing: processing that adds no value due to poor product design.
(5) Excess inventory: collect costs due to poor planning.
(6) Unnecessary movement of workers, due to inappropriate tool or work design.
(7) Defective product: products that nobody wants.
The term ‘waste’ can only be used when what exactly is the item of waste is specified. But in most of the
cases this is not clear as to what exactly is being wasted. And in a number of occasions it is seen that
‘wastes’ simply imply ‘material wastes’.
(A) Take the example of the European Waste Catalogue, the following classification is given in the
index.(Fig 2.1) The list gives a good insight into types of material wastes only. It is noteworthy to
see that the title European Waste Catalogue’ does not specify this as European Material
Waste Catalogue’.
(B) The ‘International Journal of Integrated Waste Management, Science and Technology’ gives the
following in their aims
“Waste Management is an international journal devoted to the presentation and discussion of information
on the generation, prevention, characterization, monitoring, treatment, handling, reuse and ultimate
residual disposition of solid wastes, both in industrialized and in economically developing countries”.
Although the name suggests ‘Integrated waste management’, the inherent reference to material waste is
evident in the explanation given in their aim which clearly specified solid waste’. The classification
commonly would be what as to what type of material wastes’ is being dealt with and not what type of
waste. Thus it can be concluded that material wastes are usually known synonymously as waste when and
wherever not specified.
Take another case, the journal Waste Management & Research (WM&R). It publishes articles relating to
theory and practice of waste management and research. Published on behalf of the International Solid
Waste Association (ISWA), the topics include: wastes (focus on solids), processes and technologies,
management systems and tools, and policy and regulatory frameworks, sustainable waste management
designs, operations, policies or practices. The “focus on solids” is clearly mentioned in the introductory
note in the journal.
It might seem harmless when material wastes have taken over the role of all wastes, but there are some
unintended consequences, which may have had a profound impact on other areas that are least expected.
And in our context, construction process.
3. Waste in construction philosophy
As a result of the above philosophy, the studies by construction scholars into waste are usually involved
into material waste occurring in construction sites. Thus the process of quantification of material waste is
a regular topic of study in the scholarly circle in construction research.
The journal Construction Waste: Quantification and source evaluation by Bossink et.al.(1996),
provides data regarding wastes in the Dutch Construction Industry. Consider a few statements provided in
the conclusion,
In the Netherlands, for five residential buildings projects and for large number of construction
materials, the amount of construction waste has been quantified. The research project indicates that the
main amount of solid waste in a construction project is caused by use of a small variety of construction
materials…….” (Bossink et.al.(1996)).
The conclusion gives a very clear idea that only material wastes were taken for study. But the name
suggests only construction waste. Research paper by Alwi Hampton titled “Waste in Indonesian
construction industry” suggested six factors were found to be the key variables of waste.
(1) Repair on finishing works,
(2) Waiting for materials,
(3) Delays to schedule,
(4) Slow tradesmen, and
(5) Waste of raw materials onsite and
(6) Lack of supervision.
Thus an important fact that can be drawn from the above is that although Alwi(2002) has listed the waste
variables, the details of what type of waste are these variables are not looked upon. Thus, ambiguity
regarding waste types is something that can be concluded here.
Classified waste by Ramaswamy et.al (2008) divided waste in construction into (1) material, (2) quality,
(3) labor and (4) equipment. The following figure shows detailed waste classification done. It can be seen
that the waste types have also been further divided. The classification can be seen to be a better
representative of waste types, but in this case to the primary types such as wastage in money, time,
material etc are only looked upon metaphorically.
Figure 2. European Waste Catalogue.
Figure 3. Classification of Waste provided by Ramaswamy et.al
3.1 Conclusions derived for type of waste
It is thus a rhetorical question as to what are the primary types of waste that are to be used so as to be sure
of their quantification. For the sake of ease of quantification of waste in construction, wastes in this paper
have been divided primarily into 3 namely,
(1) Money waste / Economic waste.
(2) Time waste.
(3) Material Waste.
It is worthwhile to note that all other types of wastes in construction could be broken down into either of
the three given above or its combination. As an example the waste classification given by Ramaswamy
et.al (2009) can be further broken down into the above three wastes as in the following figure.
A critical review of the findings by Alwi on the context of what type of waste, we could conclude the
following further classification.
(1) Repair on Finishing work – Responsible for time waste, money waste and to an extend material
waste depending on type of work
(2) Waiting for materials – Time Waste
(3) Delays to schedule – Time waste
(4) Slow tradesmen – Time Waste and money waste.
(5) Waste of raw materials onsite – Material Waste
(6) Lack of supervision – All wastes can be incorporated as a result of lack of proper supervision.
Figure 4. Indirect Wastages are marked in oval diagram, based on waste classification given by
Ramasamy et al(2009)
Thus, the three wastes are chosen as primary wastes for further discussion, as the ease of classification is
thus very clear.
4. Waste Reduction Techniques in concept of Lean
Lean construction aims to maximize value in construction industry by reducing wastes. The goal of Lean
Construction Institute given in their website is as follows:
“An organization that aims to extend to the construction industry the ‘lean production’ revolution started
in manufacturing” (www.leanconstruction.org).
Lean manufacturing is a successful area in production engineering which was started by successful
implementation by Toyota in its manufacturing unit. Waste reduction was achieved by implementing lean
production .
“Waste elimination is a by-product of lean process, lean design and lean production management.
Viewing it as the raison d’être, focus or purpose for lean is itself wasteful” (Alan Mossman, 2009)
Seven wastes in production are focused upon so as to maximize its reduction (known in Japanese as
‘Muda’.) They are
(1) Over Production
(2) Over Processing
(3) Wait
(4) Motion
(5) Inventory
(6) Defects
(7) Inventory
The philosophy of Toyota Production System formed the beginning of lean manufacturing. It involved
continuous development process within the production phase requiring constant waste reduction of above
7 categories. One of the main philosophies involved is to work intelligently and eliminate waste so that
only minimal inventory in needed. (Ohno, Taiichi (1988)), Today lean manufacturing is an important
component of production systems in many firms worldwide. It is only in 1992 that the idea of lean
construction from lean manufacturing put forward by Lauri Koskela came into being (Koskela, 1992). As
a result of this idea, a number of tools were thus developed with the idea of reducing wastes. They came
to be known as ‘lean construction tools’. Some of the tools developed were Last Planner System (LPS),
Master Schedule, and Percentage Plan Complete (PPC) etc. They were successfully incorporated into
construction projects and studies clearly indicate an increase in productivity as a result, although not
clearly a successful as in manufacturing. The implementation ran into a number of serious problems and
results were thus not as promising as in case of Toyota during the 1930’s. The problem thus was
something that had to be sorted out.
It is to be contemplated that construction unlike manufacturing is ‘unique’ for every project. It is also a
series of complex set of processes that are interlinked. Further the complexity of construction processes
also had had a toll in successful transfer of lean from production to construction. Findings by Bo
Jorgensen and Emmitt (2008) clearly stated
“In the transition from manufacturing to construction the process losses appear to be related to critical
aspects and the challenges surrounding practical application to a different context. Lean is highly
interpretive and there is no shared definition or understanding of what is meant by lean, lean production,
and lean construction. The focus has been mainly on production system design, planning and
management, and implementation. This narrow focus has meant that some important issues concerning
the wider aspects of lean have been overlooked. There is a need for a “back to basics” discussion on
many other aspects of the approach, such as whole-life value and waste identification.” (Jorgenson et .al
(2008))
These conclusions clearly states that whole value approach and definitions for waste are issues that
requires critical review. It might be correct to say that either the above two issues do not affect production
sector, or their impacts are small enough that make these factors of any concern. Another possibility in
this regard is being to the structural differences between production and construction. Production is highly
repetitive, more predictable and thoroughly pre plan able”.
“Manufacturers make parts that go into projects but the design and construction of unique and complex
projects in highly uncertain environments under great time and schedule pressure is fundamentally
different from making tin cans” (Howell, 1999)
Production industry does not rely too much on un predictable factors common in construction. Another
advantage that makes the whole the more different is the human factors or large number of human
involvement in any project. In construction, human factor is as important as any other factor. It has highly
scattered chain of events that are controlled by individuals that are highly unproductive, unreliable and
keep changing positions over time. To explain this, consider a study by Noulmanee. Noulmanee et al.
(1999) investigated causes of delays in highway construction in Thailand and concluded that delays can
be caused by all parties involved in projects; however, main causes come from inadequacy of sub-
contractors, organization that lacks of sufficient resources, incomplete and unclear drawings and
deficiencies between consultants and contractors.
Figure 5. Schematic overview of the diffusion of lean production – schematic overview, only main
way arrows shown. ( Jorgensen and Emmitt (2008))
The study suggested that delay can be minimized by discussions that lead to understanding. Thus delay in
Thailand is caused by 4 out of 5 factors, which are human related.
To make things worse, a whole lot of external factors have direct control on construction activities, which
is very much unlikely in production. Environmental factors, climatic factors, governmental factors,
sustainability factors etc are some to name a few. For instance, study by Ibrahim Mahamid et.al (2011)
conducted detailed study on delay of road projects in West Bank, Palestine. It identified 52 causes. They
study concluded five severe causes as the political situation in West Bank, award project to lowest bid
price, shortage of equipment, progress payment delay by owner and the segmentation of west bank and
limited movement between areas
Figure 6. Concept map for recommended factors to consider when developing weekly work plan
based on number of trades involved with the project
The result of all these may be responsible for lean construction to be lost in transition while coming from
production. As suggested by Joggerson (2008), it is high time proper definition of waste and project value
is taken into account. In this paper, based on a wider study on the defining time waste (Safeer et.al 2012),
we argue that time waste is something that is not abstract and is quantifiable. Further, find a method of
quantification alongside units of its measurements. The coming chapters deal in detail regarding these.
5. ‘Time Waste’ in Construction
Although time waste is related to delay of construction projects as a whole, a detailed study on time
wastes are not a regular area of study. Study on this area by Safeer et.al(2012) showed that delays in
construction sector are very common and are commonly documented and are a regular area of study. Also
worthwhile to say is that activity oriented time waste generation is not a regular area of interest. (Safeer et
al (2012). Apart from a few research done by a small number of scholars, the area is of little interest.
Garas et.al. (2001) identified similar 9 primary areas of time wastes. They were:
Idle time (waiting periods),
Stoppages,
Clarifications,
Variation in information,
Re-work,
Ineffective work (errors),
Interaction between various specialties,
Delays in plan activities and
Abnormal wear of equipment
Terge Kalsaas did a thorough literature study on journals spanning 30 years. Meta-analysis was conducted
and the results showed that 49.6% of time was wasted in construction activities. (Horman et.al, (2005))
Diekman et al studied wasted time in steel erection jobs. He divided the activities as Value Adding (VA),
Non Value Adding (NVA) and Pure Non Value Adding (NVAR).The results are presented in Table 1
Table 1: Percentages of Value Adding Activities. (Adapted from Diekman et al(2004))
Steel Erection job VA NVA(Waiting) NVAR
Project 1 32 60(34) 9
Project 2 11 57(24) 35
Project 3 10 67(46) 24
The study given by Geras et.al (2001) and Horman et.al(2005) and Diekman.(2004) provides only a small
insight into areas that generate time waste. But the study could still be broken down to activity based time
waste, which was not done. Further, quantification data in suitable units are lacking. One must keep in
mind that by simply identifying an overall area of time waste generation or percentage of wasted time
does not help much in finding ways to its reduction. These are clearly stated in findings by safeer et al as
follows
Some of the findings were:
1. Very little study has been carried out in detail, on the entire construction process regarding time
wastes, although partial studies pertaining to certain activities have been seen.
2. The units of time waste, for the purpose of quantification, have not been made by any scholarly
work.
3. Extensive research is required into activity oriented time wastes in construction. Study need to be
carried out on reason, causes and remedies for reduction in time waste.
4. Lean techniques adopted from manufacturing may help in reduction of time waste but extensive
study need to be carried out to adopt the lean practices in reduction of time waste in construction
process.
5. Study need to be conducted to identify causes of time waste in building construction projects and
further identification of factors that are internal and external to project. The influence of these
factors on each activities obtained by discretizing the construction project into manageable units
need to be studied along with its relative importance and its interrelationship. This
interrelationship needs to be studied between activities and between time waste factors.
(Safeer and Arun (2012))
5.1 Units of Time Waste
Time Wastes are required to be defined for activities. It can be seen that systematic addition of time
wastes in a number of activities result in overall delay of the project. Project Management tools such as
CPM PERT CCPM etc are tools that help in judicious usage of time, so that various activities are
managed in the best way available. But these methods also are not completely reliable if the activities are
not broken down to the micro level. Thus it is imperative to find out means of quantifying wasted time for
each activity. So it needs to be seen what exactly is time waste for an activity?
The previous chapters of the paper have given a good insight to different literature available in the areas
connecting time waste. They included waste, delays, lean, material waste etc. As for convenience, in
chapter 2 wastes were primarily divided into 3 in construction activities (Time Waste, Money Waste and
Material Waste). It is thus possible that every activity may have time waste associated with it in case the
planning part of it is not done properly.
From studies by Ramaswamy, it can be noted that Time waste can be of 2 types
(a) Direct Time Waste
(b) Indirect Time Waste
5.2 Direct Time Waste (DTW)
DTW can caused as a result of a number of reasons which may be human factor, technological, external
or any other regular construction delaying factors. It is directly seen in variation of time taken to complete
a work. And this can directly be noted down. The amount of losses incurred can also be found as a result
of direct TW.
Example:
Suppose Activity A was to be completed in 10 days, and it took 15 days to complete it. The direct Time
Waste is 5 days of wasted time.
DTW = 5 days worth of waste.
In order that this waste is to be reduced, findings are to be done to reduce it.
5.3 Indirect Time Waste (ITW)
ITW are those TW which remain hidden, and are not seen at first sight. Any waste in time cased that are
not in the category of direct measurement as in DTW, is categorized as Indirect Time Waste.
In Project X, Suppose Activity B was planned to be completed in 20 days. And as expected it finished in
20 days.
In Project Y, Suppose same Activity B with similar resources and conditions took only 18 days to
complete above time. Thus, it is clear that the Activity B could be completed in 18 days. A lack of good
planning had given 20 days time to complete and it was done in that time. 2 days were given in excess of
that required. Thus 2 days could have been made productive. Thus this wasted 2 days have been
categorized as ‘Indirect Time Waste’
ITW = 2 days worth of waste.
Regarding Indirect Time Waste, an important law named after C N Parkinson, the Parkinson’s Law
(published in ‘The Economist’, 1955)
“Work expands so as to fill the time available for its completion.”
One among the reasons for considering ITW would be the application of Parkinson’s Law in activity time.
The after effects being that, time when planned in excess of required would not produce best usage. Or
the tendency to become lazy increases and the time would be used up completely. The human tendency to
shift all the work to the last minute plays its toll.
Another application of Indirect Time Waste may come hidden in certain activities that are linked to other
activities. Suppose Activity C has to been ordered a rework. Thus the time that is taken in excess to
complete the activity C is DTW. But if it affects any other activity, then time wasted in that activity is
ITW, whose cause would be rework of C.
The list of ITW’s is not exhaustive. As defied above any time waste that is not directly measured out is
ITW. It is of hidden nature; hence its presence can be related to number of activities and is of complex
nature. In order to identify it, detailed study of a project is required.
Finally it may be noted that the total time waste in an activity would be the sum total of Direct Time
Waste and Indirect Time Waste. Thus,
TW = DTW + ITW Eqn (1)
5.4 Units of Time Waste.
The definitions above for time waste become incomplete without defining a proper unit for Time Waste.
Without this part of the study, the quantification becomes impossible. Henceforth, all possible units are to
be considered before considering a suitable one.
(a) The first unit that can be proposed for TW is the unit of Time i.e., days/weeks/hours etc
It is unknowingly used almost everywhere, and the the most expected one to the considered for usage. But
there are a few issues concerning time as a unit of time waste. The problem would be inconsistency
arising if quantification is to be done.
Consider for instance, Activity P has to be completed in 10 days. And it took 13 days for P to be
completed, making a delay of 3 days. Thus bringing a DTW of 3 days,
As per definitions above, DTW = 3 ‘days’.
If activity P is painting work, say the loss of 3 days do not affect any other activity drastically.
But if the activity P is digging foundation, all the subsequent activities are affected.
And if the activity P was building a slab in the first floor for a 2 storey house, activities that connected to
it such the electrical connections, building toilet if any on that slab, adjacent beam on the slab etc do get
affected.
Thus the DTW = 3 DAYS, for all the 3 cases. With no issues to be taken for when the loss of productivity
or loss of economy for the project as a whole is considered. Thus, it may be concluded that there is a
delay of ‘3 days’. And a DTW of ‘3 units’, where units cannot be days since the impact of these 3 varies
as activity P varies. Thus the units of ‘time’ are not a suitable unit for unit of time waste.
To be clearer, the amount of waste generated is not the amount of time generated. They vary. This
difference is not taken into account in a large number of scholarly studies.
(b) The second unit that can be proposed would be unit of material waste.
As the name suggest, materials can be measured by the quantity of material that is wasted. For example, if
out of 50 kg bags of Cement, only 48 bags was used for casting of roof slab, and two was wasted away,
the material waste in this case would be,
Material Waste = 2 x 50 kg bags of cement
= 100 kg cement.
As far as time waste is considered, no such physical interpretation of wasted time is available. The only
possibility would be ‘time’ itself, which, in the previous section was ruled out as a consistent unit of TW.
(c) The third unit that can be considered is man-hours of work.
This is another possible candidate for unit of TW. But here too, issues exist. Suppose a labour has to work
for 8 hours to cast a wall. It was completed only in 12 hours. And so, the waste here would be 4 man
hours. It would be ok to call here, the TW would be 4 man hours. But when other Indirect Time Wastes
come into picture, and when if another laborer has to complete painting in 8 hours. And TW is 4 man
hours, then its impact on the project is also different. The resulting wastage is different. Further, if the
there are any other losses that are not human related, such as material losses, it would not be suitable to
call ‘man-hours’ of waste, when no ‘man’ is involved in the process at all.
(d) A fourth unit that can be considered would be the unit of money.
Although least expected, the units of money does seem to fit into many of the issues that exist above.
‘Time Waste’ cannot have units of Time, but it may have the unit of waste. And in construction, all
wastages can be finally converted into unit of money. Similar in the case of TW also.
Consider activity J was to be completed in 15 days. It took 18 days to complete.
The delay in this case would be 3 days. But cost of labour, cost of excess charges, cost of materials, over
head charges etc would be all amount to say Rs.50,000/-,
Then it could be said to have a TW worth of Rs 50,000/- has occurred. This would be the case of DTW,
in case of ITW,
if an activity K was planned for 20 days when it could have been completed in 18 days, the overall
amount that could have been saved equal to say Rs 30,000/- .Then an indirect time waste of Rs 30,000/-
has been incurred. (This amount is not something that is an additional expense, but it is something that
could have been saved in case of more judicious planning procedures)
Futher, it may be noted that, in completing in 20 days, no delay of project is incurred. Only Time Waste
worth of Rs 30,000/- is incurred.
Now suppose activity K got delayed by 1 day due to environmental factors such as rain, and it took 21
days to complete, the excess cost incurred as a result is Rs 15,000/- say. Then the net TW here would be,
TW = DTW + ITW,
TW = Rs 15,000 + Rs 30,000
= Rs 45,000/-
Thus total TW worth of Rs 45,000/- has been incurred with a Delay = 1day to the project.
5.5 Graphical Interpretation of Time Waste.
Indirect Time waste, (ITW) can be graphically shown using the time-cost trade off graph. The following
figure, fig 5.1, shows a typical time-cost trade off graph. On the x-axis, the task duration, on the y-axis
task direct cost. As the task duration of the activity is to be reduced the cost has to be substantially
increased. As far as DTW is considered, there would be a direct overrun of time and as a result an
increase in cost of project. As far as ITW is considered, there
usually would be no overrun of time, but time could be contracted and hence savings in cost can be made.
The following graph explains the incidence of ITW in the time cost trade of graph.
The presence of Indirect Time waste can be incorporated in the above Time cost trade off graph. Since
ITW remains hidden, there is no physical decrease in Time but only excess cost involved. Theoretically
these could have made more profitable by better planning. But for the current case, was not done. The
following figure shows presence of ITW. It could be used to reduce TW in the future planning stages.
Figure 7. Time Cost Trade off Graph used in Critical Path Method
Figure 8. Incidence of ITW in the Cost – Time Trade off Graph
6. Conclusions
Delays In construction could possibly be reduced by reducing activity oriented time waste generated.
Possible units of time waste are considered in this paper. It has been seen that time is not a suitable unit of
time waste. Neither are man-hours nor units of material wastes make suitable substitutes for units for time
waste. The units of money are seen as a possible unit for measuring time waste successfully.
Time waste was successfully divided into direct time waste (DTW) and Indirect time Waste (ITW). Direct
time waste is the amount directly measured wasted time and the amount of economic loss incurred can be
directly measured. Indirect time waste is hidden. They are to be investigated and found out. Usually
inefficiency in planning stage can cause ITW. Due to the application of Parkinson’s law in construction
field personnel, it happens that the entire time allotted is used up for finishing a work that could have
been completed earlier. Thus wasted time is hidden, and the economic gain that could have been
benefitted, if the planning was good is one type of ITW. Further investigation is required into classifying
and identifying all type of ITW and its interrelations.
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