Identiﬁcation of Schedule-Performance Indicators and Delay-Recovery Strategies for Low-Cost Housing Projects

: Many construction projects su ﬀ er from schedule delays that ultimately lead to considerable cost overruns and defeat the purpose of low-cost housing (LCH), which is to support low-income earners. It is, therefore, vital that the schedule delays and cost overruns be minimized. The objectives of this research were to investigate, identify, and classify the schedule-delay indicators (SDIs), prioritize them based on their level of impact, and formulate constructive strategies to improve the schedule performance. To achieve the objectives set forth, 68 interviews were conducted with professionals who are active in LCH projects, and a structured survey was developed and distributed to other experts involved in LCH projects to validate the result of the interviews and collect additional data. Survey responses were collected from 101 individuals and were analyzed. The signiﬁcant SDIs were identiﬁed and classiﬁed by the research team and were ranked and prioritized, using the Relative Importance Index (RII) method. The results demonstrated that the identiﬁed SDIs could be classiﬁed into the following eight main categories: legal, design and technology, project characteristic, project management, material resource, human resource, location, and ﬁnance. The outcomes of this study will help project managers and stakeholders identify the causes of schedule delays early in the project and implement e ﬀ ective strategies for improving project performance in low-cost housing projects.


Introduction
Housing is considered a key element of human survival, as it contributes significantly to economic growth and society's general well-being [1]. In underdeveloped countries, increases in population and urbanization have led to a growing demand for low-cost housing (LCH), which is one of the most significant needs of low-income families [2,3].
Scholars and practitioners frequently encounter the challenges of schedule delays and cost overruns in construction projects [4] which negatively affect the cost of the projects and the growth of the economy. Since LCH is designed to help low-income earners, it is critical that the projects are completed on time. A lack of knowledge of the root causes of schedule delays is one of the main reasons that such projects fail [5].
Although multiple studies have been conducted to investigate causes of schedule delays through existing literature [6], the schedule performance of many construction projects is still poor [7]. This is particularly detrimental to LCH projects. This research addressed the problem by formulating the

Low-Cost Housing (LCH)
Oxley [9] defined low-income housing as a vehicle for helping households who are unable to support themselves. Similarly, UN-Habitat [10] defined low-income housing as provided housing that meets the needs of low-income individuals/families who are unable to compete in the marketplace for decent housing options.
The term "low-cost housing" has various meanings in different societies. In underdeveloped countries, low-income individuals/families in urban or rural areas are often unable to access the housing market through mortgage institutions and consequently need low-cost housing. In developed countries, such as the USA, low-income housing is usually affordable if the household can purchase or rent the housing unit for a small portion of its income [11]. Mortgage lenders consider this standard as one of the main criteria in qualifying buyers for mortgage loans.

Schedule Performance
Failure to finish construction project services on time is a common issue and leads to schedule delays, cost overruns, and in some cases, low-quality products [12]. O'Brien [13] defined schedule delays as the completion of a project beyond the agreed-upon contract deadline and/or beyond the date that the parties agreed on for the delivery of a project. In 2008, [14] described schedule delays as acts or events that extend the time to perform the task beyond the agreed-on contract deadline.
Project success with respect to a particular project participant was defined by [5] as the degree of achievements of project objectives and expectations of that participant. They also mentioned that schedule, cost, and quality are considered the three factors that most significantly impact a construction projects' success. In 2009, [15] stated that project success is strongly connected to the project parties' satisfaction, minimal disputes/conflicts/legal proceedings, safety, and environmental impacts of the project. Additionally, schedule delays commonly have negative impacts on primary and secondary stakeholders such as clients, contractors, and consultants [16].

Schedule-Performance Indicators in Low-Cost Housing (LCH)
An attribute of LCH projects is their tight schedule and congested critical path. Any delay in the project schedule would result in cost overrun which defeats the purpose of finishing the project with a low cost. As the main purposes of providing LCH is to support low-income individuals/families, delivering the projects on time is critical to preventing cost overruns. Therefore, it is important to identify the critical root causes of delays in these projects [17]. In 2014, [18] conducted a study and identified the main causes of schedule delays in housing projects as ineffective execution policies, unqualified team members, and poor leadership of the project management team.
In 2014, [19] performed a study that found the unavailability of housing loans, high lending costs or interest, short loan repayment terms, and low-quality materials as the most significant delay indicators in housing projects. In 2010, [20] concluded that unsuitable locations of housing projects was one of the main factors of low schedule performance in these projects. In 2008, [21] identified the lack of governmental support as one of the key indicators of schedule delays.

Gap of Knowledge
Identification of the root causes of schedule delays during the early stages of construction projects is important to prevent them and the resulting cost overruns from occurring [22]. Multiple studies, as indicated in Table 1, have been conducted to identify SDIs in different sectors of the construction industry. However, few studies have focused their attention on the significance of SDIs in LCH projects. Since the main target of providing LCH is to support low-income earners, delivering the projects on time and within budget is crucial. Thus, the focus of this study was to determine significant SDIs, classify them, and prioritize them based on their impact on LCH projects. Additionally, constructive best practices were developed and are proposed to improve the schedule performance of LCH projects.

Research Methodology
To achieve the objectives of this study, a five-step research framework was developed. As shown in Figure 1, the existing literature was thoroughly reviewed to identify the list of potential SDIs associated with the construction of LCH projects. An interview protocol, using the potential SDIs, was developed, and 68 professionals and experts active in LCH projects from all over the world (i.e., North America, Africa, and Asia) were interviewed, and the collected data was analyzed. To validate the results and collect additional data, a structured survey was developed based on the SDIs mentioned by the interviewees, and the survey was distributed among other experts and professionals involved in LCH projects globally. A total of 101 survey responses were collected, and, as shown in Figure 1, the collected survey data was analyzed to determine and classify the significant SDIs associated with LCH projects. The significant SDIs were ranked and prioritized, using the RII approach. In the fourth step, constructive and practical recommendations, based on the outcomes of the previous steps, were developed and proposed. The relationships between the recommendations and schedule categories were investigated, and the results were discussed in detail.

Relative Importance Index
The RII method has been previously used in different studies to calculate the relative importance of the various causes of delays [36]. The RII method was also adopted in this study to quantify the relative importance of significant SDIs. The significant SDIs were ranked and prioritized based on the calculated values of the RIIs. The SDI with the highest value of RII was ranked as first. The equation to calculate the RII is shown in Equation (1). where W, A, and N indicate "weight associated with each SDI," "highest weight" and "total number of survey questions" respectively.

Relative Importance Index
The RII method has been previously used in different studies to calculate the relative importance of the various causes of delays [36]. The RII method was also adopted in this study to quantify the relative importance of significant SDIs. The significant SDIs were ranked and prioritized based on the calculated values of the RIIs. The SDI with the highest value of RII was ranked as first. The equation to calculate the RII is shown in Equation (1).
where W, A, and N indicate "weight associated with each SDI," "highest weight" and "total number of survey questions" respectively.

Data Collection Approach
The procedures implemented to develop the interview protocol and survey questions are presented in Figure 2. A comprehensive list of the potential SDIs associated with LCH projects are shown in Figure  2. The research team's interviews with a large group (68) of experts and professionals involved in LCH

Data Collection Approach
The procedures implemented to develop the interview protocol and survey questions are presented in Figure 2. A comprehensive list of the potential SDIs associated with LCH projects are shown in Figure 2. The research team's interviews with a large group (68) of experts and professionals involved in LCH projects revealed the SDIs that they deemed the most significant, which were used to develop a structured survey to validate the results of the interviews and collect more data. projects revealed the SDIs that they deemed the most significant, which were used to develop a structured survey to validate the results of the interviews and collect more data.

Data Collection: Interview
The literature review and list of potential SDIs were used to develop an interview protocol consisting of 22 questions designed to gather data essential for identifying the critical SDIs in LCH projects. The interviews were conducted with professional and experienced participants such as general contractors, project engineers, superintendents, project managers, and finance officers who were involved in LCH projects. The interview protocol was sent to the interviewees two weeks prior to the telephone interviews. Table 2 presents the professional information of the interviewees: 17 general contractors, 17 subcontractors, 17 project managers, and 17 superintendents.

Data Collection: Interview
The literature review and list of potential SDIs were used to develop an interview protocol consisting of 22 questions designed to gather data essential for identifying the critical SDIs in LCH projects. The interviews were conducted with professional and experienced participants such as general contractors, project engineers, superintendents, project managers, and finance officers who were involved in LCH projects. The interview protocol was sent to the interviewees two weeks prior to Sustainability 2019, 11, 6005 5 of 13 the telephone interviews. Table 2 presents the professional information of the interviewees: 17 general contractors, 17 subcontractors, 17 project managers, and 17 superintendents.

Results of Interviews
The significant SDIs were determined based on the interviews conducted with 68 professionals involved in LCH projects and the results are presented in Table 3. Table 3 consists of five columns: the number assigned to the SDI, category, schedule-delay indicator, frequency of responses, and percentage of responses. The research team classified the SDIs into different categories that were inspired by existing literature [11,30]: project management, human resources, material resource, legal, design and technology, finance, and project characteristics. As indicated in Table 3, the entire group of expert interviewees believes that inefficient site management and supervision, belonging to the category of project management, is a significant SDI associated with LCH projects. Inefficient site management and supervision can lead to the issuance of change orders that may modify the design in the later construction stages of LCH projects, which might cause major delays in the delivery of a service and consequently decrease the schedule performance.
As shown in Table 3, all 68 of the professional interviewees believe that one of the critical indicators leading to substantial schedule delays in LCH projects is the lack of qualified team management members, which belongs to the human resource category. The project management team is commonly responsible for applying the knowledge, skills, tools, and techniques that are necessary to deliver the project's objectives. Therefore, a dearth of qualified managers results in improper manipulation of the project tasks and personnel and consequently leads to inefficient coordination and an increased rework. Thus, the schedule performance of the LCH projects is negatively impacted.
All the interviewees stated that inefficient logistics and material supply, belonging to the material resource category, is one of the main SDIs in LCH projects and causes inefficient planning, execution, control of procurement, transportation, and stationing of material. These SDIs tend to increase the duration and decrease the schedule performance of the projects.
As shown in Table 3, most of the interviewees (98.5%) believe that delays in the approval of submittals, design drawings, and shop drawings, belonging to the legal category, is one of the main SDIs in LCH projects. Delays in approval squanders the workers' time and as a result, increases the number and frequency of schedule delays.

Data Collection: Survey
After identifying a list of potential critical SDIs from existing literature and performing the interviews, a survey was developed that consisted of five-point Likert scale questions associated with significant SDIs. The survey included three main sections: general information, causes of schedule delays, and recommendations. Each of the identified SDIs became one question in the second section of the survey. Five sample questions belonging to the category of project management are presented in Figure 3.  The survey was distributed to qualified professionals and experts involved in LCH projects, and 101 survey responses were returned to the research team. The demographic information of respondents is presented in Table 4. Participant profiles illustrate that 38 respondents (37.6%) had five years or less work experience in LCH projects, approximately 37% of the respondents had more than five years, and equal or less than ten years job experience in LCH projects. As shown in Table 4, 27 (26.7%) of the respondents were project engineers, and 24 (23.8%) of the respondents were project managers.  The survey was distributed to qualified professionals and experts involved in LCH projects, and 101 survey responses were returned to the research team. The demographic information of respondents is presented in Table 4. Participant profiles illustrate that 38 respondents (37.6%) had five years or less work experience in LCH projects, approximately 37% of the respondents had more than five years, and equal or less than ten years job experience in LCH projects. As shown in Table 4, 27 (26.7%) of the respondents were project engineers, and 24 (23.8%) of the respondents were project managers.

Data Analysis of Collected Survey Responses
The value of RII associated with each SDI was calculated and is presented in Table 5. "Scope creep", belonging to the legal category, received the highest value (0.75), based on the RII method, and was ranked first among the significant SDIs. Scope changes often lead to the issuance of change orders in the field and/or design modifications and thus seriously affect the schedule performance of LCH projects by requiring extra time to complete the project.  Table 5 shows that "design changes/modifications," belonging to the design and technology category, received the second highest ranking among the significant SDIs, with an RII value of 0.74. Design changes and/or modifications can occur due to many factors, such as financial issues, quality of material/equipment and lack of craft labor experience which cause major negative impacts on the project completion time and schedule performance of LCH projects. Table 5 indicates that the third highest ranked SDI is "unrealistic baseline schedule", belonging to the project characteristic category. The unrealistic baseline schedule SDI causes schedule delays for all activities throughout the execution phases of LCH projects. A tight schedule may cause delays in delivery of the equipment, tools, and materials, and lead to considerable schedule delays in LCH projects.
The survey respondents ranked "ineffective communication and coordination" as the fourth highest ranked SDI in contributing to low schedule performance in LCH projects. Lack of effective communication and coordination can drive numerous challenges associated with conflicts among the LCH project parties and prevent important information and knowledge from being disseminated among the project parties in a timely manner [37]. Major schedule delays can result from lack of communication and coordination throughout the execution of LCH projects.

Recommendation
In the last step, the respondents were asked to provide recommendations that might help reduce and/or prevent delays in LCH projects. The recommendations are presented below.

Early Identification of Errors in Planning and Specifications
As "design changes and modifications" attribute to schedule delays in construction projects [38,39], it is very important to identify their root cause. The professionals who were involved in LCH projects stated that errors and omissions in the planning and specification stages are a key cause of reworks. Therefore, it is very important to identify the mentioned errors and omissions early in LCH projects so that the reworks can be minimized or prevented.

Prevention of Complex Design
When the design of a system is complex, there is an increased potential for errors that lead to design changes and modifications during the construction phase. This is probably attributable to multiple factors, such as deficiencies in the designers' knowledge and/or experience [40]. To prevent these challenges, architectures/engineers need to conduct an initial constructability analysis to prevent the possibility of design changes in the construction of the LCH projects.

Development of Realistic Schedule
The project schedule is frequently established before the scope of the project is well-defined and the project team is finalized. Unrealistic deadlines put unnecessary pressure on the staff and project management team who are expected to deliver services on time. In addition, the number of design changes and modifications often increase as the project progresses [41], and leads to schedule delays. Therefore, it is vital that a realistic and reasonable schedule project is developed to ensure that the construction activities can be completed in the time allotted. Collaborative planning strategies such as the use of Lean construction methods such as the Last Planner System (LPS) could help alleviate the challenges associated with unrealistic schedules [42].

Establishment of Effective Communication
The establishment of effective communication among different project parties is commonly considered to be one of the main responsibilities of the project management team. As each of the project parties has unique set of experience, knowledge, and skills, reaching an agreement is often challenging and time-consuming [43]. Ineffective communication may cause an increase in the number of design changes and/or modifications in a project; thus, effective communication among the project parties is one of the most efficient ways to avoid conflicts that can delay the project.

Implication of Advanced Tools and Techniques
Multiple advanced tools and techniques have been developed to improve the performance of construction projects and decrease the number and cost of reworks in projects. Building Information Modeling (BIM) is one of the advanced tools [44] that is very useful for improving project performance and decreasing the number of change orders in LCH projects. The professionals and experts involved in LCH projects suggested implementing BIM software platforms such as Navisworks to help the construction management team identify clashes early in the design of projects which can in turn result in cost saving for LCH projects.

Relationship Between Schedule Performance and Recommendations
The research team analyzed the relationships between the SDIs and the five recommendations. The results are presented in Table 6. Two of the recommendations are particularly important to improving the schedule performance in LCH projects: the implementation of advanced tools and techniques, which helps laborers with minimal experience and skills execute projects effectively, with few errors; and early identification of errors in planning and specifications, which leads to a considerable reduction in design changes and/or modifications.
The research team analyzed the relationships between the eight schedule-performance categories and five recommendations, and the results are presented in Figure 4. This figure illustrates that the adoption of the three recommendations, namely "early identification of errors in planning and specifications", "development of a realistic schedule" and "establishment of effective communication" would help reduce the number of schedule delays in LCH projects caused by SDIs belonging to the project management category. Figure 4 also indicates that implementing three strategies, "adoption of advanced tools and techniques", "prevention of complex designs" and "early identification of errors in planning and specifications" can help reduce the number of schedule delays that belong to the design and technology category. The research team analyzed the relationships between the eight schedule-performance categories and five recommendations, and the results are presented in Figure 4. This figure illustrates that the adoption of the three recommendations, namely "early identification of errors in planning and specifications", "development of a realistic schedule" and "establishment of effective communication" would help reduce the number of schedule delays in LCH projects caused by SDIs belonging to the project management category. Figure 4 also indicates that implementing three strategies, "adoption of advanced tools and techniques", "prevention of complex designs" and "early identification of errors in planning and specifications" can help reduce the number of schedule delays that belong to the design and technology category.
As shown Figure 4, the elimination of complex designs in LCH projects could potentially prevent delays in LCH projects by precluding the issuance of major design changes and modifications belonging to the design and technology category. The execution of a complex design for an LCH project might require skilled, experienced, and qualified team management members and laborers, as well as advanced technologies and equipment, resulting in many design changes and modifications and schedule delays. Therefore, it can be concluded that the elimination of complex designs in LCH projects would help mitigate schedule delays. As presented in Figure 4, establishing effective communication could reduce schedule delays related to finance in LCH projects. Since funding delays have negative impacts on the quality of a delivered service, such as an insufficient number of qualified project management team members and laborers, and inadequate materials and equipment, the process of reaching an agreement becomes more time-consuming. Delays in payments also result in discouraged staff and project members, and seriously affect their As shown Figure 4, the elimination of complex designs in LCH projects could potentially prevent delays in LCH projects by precluding the issuance of major design changes and modifications belonging to the design and technology category. The execution of a complex design for an LCH project might require skilled, experienced, and qualified team management members and laborers, as well as advanced technologies and equipment, resulting in many design changes and modifications and schedule delays. Therefore, it can be concluded that the elimination of complex designs in LCH projects would help mitigate schedule delays.
As presented in Figure 4, establishing effective communication could reduce schedule delays related to finance in LCH projects. Since funding delays have negative impacts on the quality of a delivered service, such as an insufficient number of qualified project management team members and laborers, and inadequate materials and equipment, the process of reaching an agreement becomes more time-consuming. Delays in payments also result in discouraged staff and project members, and seriously affect their motivation to work efficiently and deliver the project on time. These challenges and issues normally generate several difficulties during the execution of an LCH project and increase the probability of schedule delays, but the establishment of effective communication could be constructive in mitigating those issues.

Conclusions
This study aimed to determine, classify, and prioritize the critical root causes of schedule delays in LCH projects. Recommendations were also formulated and the relationships between the recommendations and schedule performance were studied and analyzed. The results revealed that "scope creep" was the highest ranked SDI and can seriously affect the schedule performance of LCH projects, requiring extra time and money to complete the projects. "Design changes and modifications" was ranked second highest among the identified SDIs in LCH projects and can lead into many issues, such as financial challenges, changes in the required material types and equipment, and lack of experienced craft labor, all of which negatively impact the schedule performance of LCH projects.
The respondents made multiple constructive suggestions on how to decrease schedule delays in LCH projects, such as: (1) early identification of errors in planning and specifications, (2) prevention of complex designs, (3) development of realistic schedules, (4) establishment of effective communication, and (5) implementation of effective tools and techniques. It was concluded that if project management met the challenges inherent in the five above named areas, it would greatly improve the schedule performance in LCH projects. The outcomes of this study can assist practitioners in evaluating the causes of schedule delays early in the project, and in adopting effective and efficient best practices to improve project performance in the construction of LCH projects.
Author Contributions: E.S. wrote the original draft, S.K. and R.A. reviewed and edited, and B.A. conducted formal analysis of this study.
Funding: This research received no external funding.