# Integration of Cost and Work Breakdown Structures in the Management of Construction Projects
## 2 Literature Review
### Work Breakdown Structure (WBS)
#### 2.1.2 WBS in the Construction Industry  
Tracking is necessary at all project execution stages [17]. However, the approval and implementation of changes at the planning stage of the project usually have a lower cost impact [38]. Later, during the execution stage, the measurement of work in progress is one of the most pressing problems for project managers [39]. In fact, accurate and up-to-date measurement of work in progress is essential for other PM functions such as schedule and cost control, financial reporting, change requests, and legal claims [40]. It is in this context that the WBS can be used by contractors as an evaluation tool (especially in large projects) [41; 42]. The specific choice when drafting this kind of WBS depends mainly on three issues [43]:  
1. The decomposition criteria, grouping activities into construction units assigned to the different contractors, and/or subcontractors involved in the execution of the project. 2. The degree of work complexity and level of detail that identifies the sequence and other relations between the activities in a logical flow of execution. 3. The criticality of the tasks, being defined in terms of units of work, according to their importance to avoid activity preemption. Hence, there must be some logical pattern (decomposition criteria) in the way the activity tasks are subdivided [44]. For any significant project there usually is more than one correct way of breaking down the project work (according to the physical parts of the project, organizational patterns or work, allocation by managers and supervisors, etc.) [45]. The use of adequate WBS templates may help clients, contractors and consultants, particularly at the planning stage. More precisely, it can offer guidance to avoid important omissions at the conceptual and detail design and construction stages [46]. Despite this, decomposition criteria will still vary across organizations and projects as they involve some subjectivity [47]. In order to define consistent decomposition criteria, the considerations indicated in Table 2 must be observed [43]. Regarding the level of detail of the decomposition, there is no uniform criterion either. Still, depending on the industry, organizational culture, and type of contract, a series of guidelines can be provided. For example, for effective project planning and control, the WBS must reflect an appropriate level of detail, reflecting the extent of decomposition and the sizing of the WPs [16]. This level of decomposition must be balanced with the administrative burden costs of managing them [48]. Some organizations also have general guidelines to make it easy to identify this optimum level of detail (emerging as one of main purposes of their PM offices). These are typically expressed in terms of effort or elapsed time, but do not usually consider the activities' specific aims [49]. Some researchers have also proposed alternative approaches, such as breaking down the project into 40-h work elements [50] (a person's work week), with no need to break it down further. Others have established that it is pointless to decompose the project elements once they represent less than 4% of the total project in time or cost [51]. \begin{table}
\begin{tabular}{c c} \hline \hline
**Criterion:** & **Comment** \\ \hline Global Vision: & Integrate to simplify, prevent omissions, and allow global analysis of the deliverable \\ Strategy: & Segregate to facilitate cross-referencing and save resources \\ Homogeneity: & Share measurement units and measurement approaches \\ Appraisal: & Be executed by a single trade to be paid once completed \\ Equity: & Make the investment profitable avoiding construction units \\ Analysis: & that are executed separately \\ Normalization: & Meet aggregation criteria for cost analysis \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Decomposition criteria to construction unit level. As a general rule in construction projects, seven criteria can be considered to stop further subdivision of project tasks [52]:  
1.