Rating the significance of the factors influencing shortage of skilled labours for sustainable construction: a perception of Makkah construction practitioner

The construction industry is one of the main economic sectors that contribute significantly to social and economic development. However, the lack of skilled labour is one of the factors affecting the success of projects in the construction industry. Skilled labours are the potential for enhancing overall delivery of construction projects to achieve sustainability. Building and construction industry in Makkah has continued to respond to shortages of skilled labours. Hence, the purpose of this study is to evaluate the importance of factors influencing the shortage of skilled labours from the perceptions of construction practitioners. In order to achieve the aims and objectives of this study, the quantitative descriptive method was adopted for this research study, and data for this study was collected through a stratified random sample of construction practitioners in Makkah. Data were first analysed by way of Analysis of Variance (ANOVA), followed by Relative Importance Index (RII) for ranking comparison among the construction practitioners. The results of RII indicates that the significant factors influencing the shortage of skilled labours in Makkah include delay in salary payment, low wages structure, lack of motivation system, health and safety issues on construction sites, lack of job security, bad relations between skilled labours and management team, poor living conditions, Slow recruitment of skilled labours, restricted government regulations, and exposure of climate conditions. The findings revealed that the factors rated are required for organisational performances which are essential in achieving sustainable building and construction in Makkah.


Introduction
Sustainable construction highlights the need to balance economic, social and environmental goals to address human needs [1,26]. This is due to the fact that construction industry is dynamic and contributes to production of most amenities which is necessary to improve the living standard of any nation [8]. Though, the performance of construction industry to achieve sustainable development depends on its human resources [25,39]. This includes professionals, skilled and unskilled labour [12]. In most countries, these human resources cover 30-50% of the overall project cost, depending on the nature of the project [32]. Kazaz and Acikara [23] and Kumarasinghe and Hadiwattege, [24] emphasised that skilled labour has the biggest impact on construction operations through the task performed. The task performed can be tied to particular skills possessed. These skills trades involve masonry, joinery/ carpentry, tiling, fabrication, plant/equipment operator, thermal/acoustic insulation, electrical services, plumbing and painting. Though, various studies have reported that there is a shortage of skilled labour in Makkah construction industry [4,5]. This poses concern as Saudis' vision 2030 will necessitate increased provision of infrastructure to attain sustainable development. In view of this concern, factors influencing skilled labours have been perceived to characterised issues regarding skilled labours supply to the construction industry. From the review, it was informed that previous studies on factors influencing shortage of skilled labour appear to consider the view from project managers and construction managers [4]. It is in this light, this study takes into account building and construction practitioners' (architects, civil engineers, mechanical engineers, electrical engineers and building engineers) perceptions to be expedited to align with the Makkah construction industry.

Literature review
The few studies that have focused on the need for more varied supply of skilled labour in the construction industry, and have proposed a comprehensive and concise list of factors that match those found in the construction industry of developing countries [4,9,19,23,27,28,40,[44][45][46]. These factors offer an opportunity to understand the shortage of skilled labour in the construction industry. For example, workers poor living condition induced an unemployed skilled worker to look for opportunities in other industries, and when the economy recovers the skilled workers are reluctant to return to the construction labour market, thus influencing shortage of skilled workers [4]. Also, lack of job security has been considered a major factor influencing shortage of skilled workers where skilled workers enjoy little or no social protection [28]. For instance, during the bumper periods, construction industries enjoyed an influx of capital leading to a builder's market with abundant construction work than during economic recession which leads to retrenchment of skilled workers, and when the economy recover the skilled workers are reluctant to return to the construction labour market, thus influencing shortage of skilled labour [44]. Besides, in most developing countries, there is no regulation guiding minimum wage for construction workers. Bilau et al. [9] put forward that different wages are paid in across construction organisations which can be erratic depending on construction projects. In addition, skilled workers potential is boundless but it requires motivation in order to excel [46]. Ironically, the majority of construction firms in developing countries do not motivate their skilled workforce for improved performance and productivity [19,40]. Besides that, poor working conditions of skilled workers have influenced shortage of skilled workers where they have no clear career paths, thus, enjoy no promotion opportunities [45]. Thus, skilled workers seek permanent jobs with clear career paths of promotion opportunities and insurance protection as a guarantee to their life for the future [41,43].
Construction has been one of the most hazardous industries as measured by the number of accidents. Thus, it is being labelled as 3D images of dirty, dangerous and difficult. Similarly, the poor image of the construction industry has unfavourably affected popularity as a career choice [38]. The image is low among workers themselves as the majority of construction skilled workers of various ages and experience would never recommend their trade to their children [37]. Other factors influencing shortage of skilled labour identified by previous researchers include long working hours for more than ten working hours per day, delay in salary payment, restricted government regulations, exposure of climate conditions, long distance from family, bad relations between skilled labours and management team, poor site accommodation, geographic location of the project, slow recruitment of skilled labour and frequent changes of skill requirement [4,23,40,46].

Nature of construction industry in Makkah and type of involved labours
Saudi Arabia's construction market is thought to be the largest and fastest-growing in the Gulf [6]. The country is worldly wide known by the biggest oil exporter resulting in increased government investment on infrastructure and construction projects. Because of this, the Saudi economy is constantly expanding, and activity in the construction sector in particular has increased significantly. According to Alrashed et al. [6], the Saudi Arabian government has allotted a significant amount of money for the building sector. Construction is presently valued at USD 600 billion till 2020, according to Saudi Arabia's Industrial Sector Overview Report from 2016. Due to Saudi Arabia's among the fastest-growing populations, there is a greater need for housing, healthcare, education, and other services. The construction industry, on the other hand, is experiencing financial difficulties as a result of rising military spending, a drop in oil prices, the country's deteriorating financial situation, youth unemployment, and declining financial reserves. Additionally, the Saudi Arabian construction industry is plagued by persistent issues such cost overruns, delays, poor safety, and low quality [13,34,35].
(If a construction project is finished on time, under budget, and with good quality, it can be deemed successful [30]. The construction sector in Makkah was subjected to a modeling investigation by Rahman et al. [34] that J. Umm Al-Qura Univ. Eng.Archit. (2023) 14:13-25 | https://doi.org/10.1007/s43995-023-00013-5 Original Article 1 3 examined 37 delay factors. Findings showed that the most important group to influence construction projects in Makkah, Saudi Arabia, was the client and consultant group. Additionally, Saudi Arabian construction workers face a number of problems, including low productivity, a lack of competent labour, bad living conditions, low compensation, delayed salary payments, inadequate transportation, injuries, and fatalities [7]. Consequently, the performance of the entire project is impacted by these issues, both directly and indirectly. Only foreign male employees make up the majority of Saudi Arabia's construction labourers [7]. They are either immigrants who were born domestic workers or foreign employees. These construction site personnel are divided into three groups based on their talents and academic level. Unskilled site workers make up the lowest class, semi-skilled site workers make up the middle class, and skilled site workers make up the highest class [7]. Therefore, all three of these worker types are necessary for the construction sector, but competent workers are preferred because they can complete construction duties correctly.
Saudi construction industry prefers foreign workers due to the high cost of Saudi labour, negative social and cultural perceptions and attitudes toward manual and low status jobs, the fact that expatriates are more disciplined than Saudis, the fact that Saudis have less English language proficiency and technical skills than expatriates, and finally the fact that Saudi employees are less willing to relocate for work. As a result, employers favor hiring international labour for their companies over local ones. According to the 2016 Saudi Arabia Manpower and Employment Report, 4.4 million expatriates are employed in the construction sector overall [3].
The most lucrative industries for this development are those related to real estate, infrastructure, hospitality, and retail. In Makkah, there is a huge demand for hotel rooms, particularly during the holy months of Ramadan and Hajj. During these times of year, the hotels are typically completely booked. Despite the presence of various hotels, Makkah city still lacks enough rooms to house tourists. According to Mostafa and Al-Buzz [29], more than USD100 billion has been set aside for the building projects being undertaken in Makkah city, including the construction of the Grand Mosque (Al-Haram mosque), in an effort to enhance the services provided to the millions of pilgrims who travel there to perform the Hajj and Umrah.
Elawi estimates that in just six years, the government has spent around USD10.6 billion on the expansion of the Holy Mosque (2010-2015). The Abraj Kudai, Abraj Al-Bait (Makkah Royal Clock Tower Hotel), the extension of the Grand Mosque, the Jabal Omar development project, King Abdul Aziz Road (KAAR), and other large and wellknown projects are available and presently being built in Makkah City. These construction projects encountered failures in terms of timely, affordable, high-quality, and safety-required completion. As a result, the focus of this essay is on the reasons why large-scale construction projects in Makkah, Saudi Arabia, fail [4].
In an attempt to provide a significant overview and evaluating the factors influencing shortage of skilled labours for sustainable building and construction in Makkah, the studies have identified seventeen factors influencing shortage of skilled labour from international studies, as presented in Table 1. It implies that understanding of this aspect is important as it is perceived to characterised issues regarding shortage of skilled labour to the building and construction industry. Hence, it is this gap of determining the significant factors influencing shortage of skilled labour that is the main stimulus for this study.

Research methodology
Research methodology is considered as a systematic approach, which mainly focused on finding answers for all research inquiries and to produce effective results of a specific study [11]. In order to achieve the aims and objectives of this study, descriptive methodology with a systematic approach is adopted to provide a full background with the most knowledge that explains the phenomenon (perceptions of perceptions of Makkah construction practitioners in rating the significance of the factors influencing shortage of skilled labours for sustainable construction), then it will be circulated after the confirmation of results in order to lead the researcher to obtain the targeted results [11].

Study tool
The current study aims to evaluate the significance of the factors influencing shortage of skilled labours for sustainable construction: A perceptions of Makkah construction practitioners, therefore, the questionnaire was used as a tool for this study, with reference to a group of literature and previous studies, to measure the variables arising from the hypotheses and model of the study and to answer their questions. The questionnaire is the most widely used scientific research tool, and it is considered one of the best means of collecting information about the study community and for its relevance to the nature of this study in terms of effort and capabilities and the spread of the study community members in far and different places.

Questionnaire
The data required for this study was gathered through the use of questionnaire survey before carrying out quantitative analysis. Using survey method, questionnaires were administered on respondents with adequate knowledge of the skills shortage issue in the construction industry, these include engineers, architects, civil engineers, mechanical engineers, electrical engineers, and building engineers in region of Makkah in Saudi Arabia.
The main reason for selecting these building and construction practitioners is due to their experience in construction activities, they are believed to have better insight and provide better evaluation and necessary information about the significance of the factors influencing shortage of skilled labours for sustainable construction and how to alleviate skills shortage in the construction industry. The questionnaire survey were centered on literature reviews which revealed seventeen (17) factors influencing shortage of skilled labour by previous researchers in the last 10 years as shown in Table 1. Consequently, a pre-test study was carried out in the form of expert validation to ensure clarity of the questions and ease of completing the questionnaire. Five (5) academics having a strong background of construction participated in this process and suggested a few changes to the questionnaire regarding the wordings of the questions. The questionnaire was then modified based on the feedback before it was finally used at the data collection stage. The questionnaire consists of respondents' personal particulars such as membership of professional bodies, years of experience, academic qualification, and numbers of projects executed (Section A). In section B, each respondent was asked to rate the factors influencing shortage of skilled labour on a five-point Likert scale ranging from 1 to 5, where 1 represents "Insignificant" and 5 represents "Very significant".

Sample structure
The population of this study were targeted on 400 drawn building and construction experts with more than 15 years of experience in the Makkah construction industry. This was intended to gather data from respondents who are considered more experienced and hold a higher position in their respective construction organisations. This is in agreement with Pradhan and Jena, [33] who emphasised that more in-depth understanding can be gathered from highly experienced experts. Consequently, a list of experts was compiled through the building and construction experts' directory. This made the task of finding each expert achievable. Thus, the questionnaire was delivered to the experts through email to ensure easy targeting specific segments from the population. Table 2 shows a summary of the sample responses of the questionnaire survey. From Table 2, the response rates were 112(74.67%), 78(78.0%), 33(66.0%), 27(54.0%) and 27(54.0%) for architects, civil engineers, mechanical engineers, electrical engineers and building engineers respectively. This was considered adequate for analysis based on the assertion by Spillane et al. [42] that the result of a survey could be measured as biased if the return rate was lower than 30%.
Sample size of this study was determined using the following formula [15]. Zaki et al. [45] where SS = Sample Size, Z = Z value (1.96 for 95% confidence level), P = percentage picking a choice, expressed as a decimal (0.5 used for sample size needed), C = margin of error (9%).

Data analysis and discussion
The data was analyzed using the following methods;

Analysis of variance (ANOVA)
The mean scores of the responses from the building and construction experts were analysed using ANOVA to test whether the responses from the five groups of experts could be treated equally. This will provide the basis which supports the opinions of the building and construction experts. The parameters used in the ANOVA are the level of significance (5%) in the mean scores of each variables and the strength of the difference otherwise called effect size for making decisions. A test result in the mean scores of each variable shows a statistically significant difference where the p-value is less than 5% level of significance. This determines the decision rule for accepting or rejecting a hypothesis. While, the effect size was calculated using the Eta squared, which classify the effects as small (0.01), medium (0.06) and large (0.14). Accordingly, the results in Table 4 revealed that there was no significant difference at p > 0.005 in the mean scores for health and safety issues on construction sites, lack of motivation system, poor living conditions, delay in salary payment, restricted government regulations, exposure of climate conditions, bad relations between skilled workers and management team, poor site accommodation, slow recruitment of skilled workers, lack of job security, and frequent changes in skill requirement. The strength of the mean difference was also small, based on the effect size calculated using Eta squared. However, there was a significant difference at p < 0.005 in the mean scores for long working hours for more than ten working hours per day, low wages structure, long distance from ss = Z 2 * P(1 − P)∕C 2 family, poor image of construction jobs, geographic location of the project and poor working conditions. Despite the significance difference, the strength of the mean difference ranges from quite small to medium with a value of 0.07, 0.06, 0.04, 0.08, 0.04 and 0.09 respectively based on the effect size calculated. Overall, this implies that the means did not differ among the building and construction experts on the factors influencing shortage of skilled workers in Makkah construction industry. Thus, the null hypothesis was accepted (Table 3).

Relative importance index (RII)
The data was analyzed using the Relative Importance Index (RII) comparison of ranking among building and construction experts. The values of the RII range from 0 to 1. The closer the RII to 1, the more important. Thus, the output of each variable was rated on the basis of the importance weighting or the proposed efficiency of each variable. Hence, the item with the highest index is the first in the rank order. This type of scale has been found acceptable in several construction management studies as an excellent approach for gathering the respondent's responses of the variables rated on an ordinal scale [14,16,22,36]. From the responses, RII was calculated using the following formula, where n1 represents the number of respondents who answered 'very significance' , n2 represents the number of respondents who answered 'significance' , n3 represents the number of respondents who answered 'moderately significance' , n4 represents the number of respondents who answered 'less significance' , n5 represents the number of respondents who answered 'insignificance' . Table 4 shows that RII values from architects ranged between 0.893 and 0.657. While, Table 5 shows civil engineers RII values ranged between 0.0.931 and 0.615. Also, Table 6 shows mechanical engineers RII values ranged between 0.872 and 0.672. Table 7 revealed that RII = 5n 1 + 4n 2 + 3n 3 + 2n 4 + n 5 5 n 1 + n 2 + n 3 + n 4 + n 5 While, low wages structure was ranked as topmost by electrical engineers, mechanical engineers and building engineers, second by architects and civil engineers. Also, lack of motivation system was ranked third by architects,  civil engineers, mechanical engineers and building engineers, and second by electrical engineers. Lack of job security was ranked third by mechanical engineers and building engineers, fourth by architects and electrical engineers, and fifth by civil engineers. Besides, health and safety issues on construction sites was ranked third by the mechanical engineers and building engineers, fourth by civil engineers, and fifth by architects and electrical engineers. Though, poor image of construction jobs was ranked fourteenth by architects, fifteenth by mechanical engineers, sixteenth by building engineers, and seventeenth by civil engineers and electrical engineers. Consequently, the ranking of each building and construction experts were evaluated to have a general agreement. This is in line with the suggestion by Chan and Kumaraswamy, [10] as more convenient for grouping the respondents' ranking of the variables. Following  Table 9.
Hence, the mean of RII values was derived by dividing the sum of RII values by the total number of factors to establish the level of agreement. This is expressed below mathematically; Mean;13.443 = 0.791 In relation to the level of agreement presented above, Akadiri, [2] marks the cut-off points for interpretation as follows,Strongly disagree (SD)-below the mean but less than 0.10; Disagree (D)-below the mean but greater than 0.10; Moderately agree (MA)-equal to the mean; Agree (A)-above the mean but less than 0.80, and Strongly agree (SA)-above the mean but greater than 0.80). Therefore, the results which fall in the first and second levels should be dismissed, as it does not represent the mean perception of the building and construction experts. Accordingly, from the above mentioned levels, RII values of factors such as; poor image of construction jobs (0.659), long distance from family (0.659), poor working conditions (0.712), geographic location of the project (0.720), poor site accommodation (0.733), long working hours for more than ten working hours per day (0.753), frequent changes in skill requirement (0.770), were below the mean, and their level of agreement ranges from strongly disagree to disagree. The results showed that there are many common factors among the respondents regarding the factors affecting the shortage of skilled labour in construction projects, such as health and safety issues, low wages structure, delay in salary payment at construction sites and other mentioned factors. But there are some factors that are important to some and unimportant to some of the respondents, such as long distance from family, poor site accommodation and other factors. It is expected that the reasons for the differences between the respondents are that these factors vary in importance according to the job and location of each of the respondents in construction projects.
Based on the outcome, ten factors; delay in salary payment (0.908), low wages structure (0.906), lack of motivation system (0.869), health and safety issues on construction sites (0.853), lack of job security (0.851), bad relations between skilled labour and management team (0.827), Poor living conditions (0.823), Slow recruitment of skilled labour (0.808), restricted government regulations (0.797), and exposure of climate conditions (0.975) are above the mean, the results which was considered by evaluation as the factors influencing shortage of skilled labour in Makkah construction industry. Accordingly, the findings shows delay in salary payment as a significant factor influencing shortage of skilled labour. Al-Emad and Rahman, [4] and Sangole and Ranit, [40] have identified poorly saving of part of advance payment from the beginning of the project and lack of efficient control in the project resources as the causes of delay in salary payment. Low wages structure was also revealed as a significant factor influencing shortage of skilled labour. The result is in agreement with Ismail and Yuliyusman, [21] who affirmed that low wages prompt construction skilled workers to pursue another career for better remuneration. Lack of motivation of skilled labour was also revealed as a significant factor, which may be due to absence clear career paths and promotion opportunities. Norhidayah et al. [31] acknowledged that the issue of motivation prompt construction skilled labour to pursue other careers for better incentives. The result shows health and safety issues on construction sites as a significant factor influencing shortage of skilled labour. This may be due to existence of dirty, difficult and dangerous image that has always been associated with this industry has indirectly discouraged many workforces from staying away from entering the construction industry [17,18]. This finding agrees with the contention of Al-Emad and Rahman [4] asserting that most of construction projects in Makkah are high rise projects and workers are not well train to strictly follow the safety requirements to avoid injuries and fatalities at sites. Based on the outcome, ten factors; delay in salary payment (0.908), low wages structure (0.906), lack of motivation system (0.869), health and safety issues on construction sites (0.853), lack of job security (0.851), bad relations between skilled labour and management team (0.827), Poor living conditions (0.823), Slow recruitment of skilled labour (0.808), restricted government regulations (0.797), and exposure of climate conditions (0.975) are above the mean, the results which was considered by evaluation as the factors influencing shortage of skilled labour in Makkah construction industry. Accordingly, the findings shows delay in salary payment as a significant factor influencing shortage of skilled labour. Al-Emad and Rahman, [4] and Sangole and Ranit, [40] have identified poorly saving of part of advance payment from the beginning of the project and lack of efficient control in the project resources as the causes of delay in salary payment. Low wages structure was also revealed as a significant factor influencing shortage of skilled labour. The result is in agreement with Ismail and Yuliyusman, [21] who affirmed that low wages prompt construction skilled workers to pursue another career for better remuneration. Lack of motivation of skilled labour was also revealed as a significant factor, which may be due to absence clear career paths and promotion opportunities. Norhidayah et al. [31] acknowledged that the issue of motivation prompt construction skilled labour to pursue other careers for better incentives. The result shows health and safety issues on construction sites as a significant factor influencing shortage of skilled labour. This may be due to existence of dirty, difficult and dangerous image that has always been associated with this industry has indirectly discouraged many workforces from staying away from entering the construction industry [17,18]. This finding agrees with the contention of Al-Emad and Rahman [4] asserting that most of construction projects in Makkah are high rise projects and workers are not well train to strictly follow the safety requirements to avoid injuries and fatalities at sites.
Government policies on construction organisations is also one of the significant factors influencing shortage of skilled labour. This is in agreement with Al-Emad and Rahman [4] found that government restrictions to skilled non-Muslim foreign workers, restriction to form union/ association and unfriendly authoritative rules has pushed many skilled labour away from the industry. This policy is a significant source of concern as skilled labour are of the view that their skills are not appreciated by the government. The result also shows exposure of climate conditions as a significant factor influencing shortage of skilled labour in Makkah construction industry. Hearly et al. [20] acknowledged that this issue is rooted in skilled labour working without requisite Personal Protective Equipment (PPE) and protection required despite prolonged exposure to climate conditions.

Conclusion and recommendations
The city of Makkah's construction sector has a variety of difficulties that make it difficult to complete projects successfully. The city of Makkah's construction sector has a variety of difficulties that make it difficult to complete projects successfully. The stakeholders in the construction industry need to pay greater attention to this in order to boost performance and guarantee the completion of construction projects. The importance evaluating the issues affecting the shortage of skilled labours for sustainable building has been identified in this article. The results of this study will assist researchers better understand the complex problems affecting construction projects in Makkah city as well as the construction community in Makkah and throughout Saudi Arabia. The problem of skill shortage in the construction industry has affected the quality and productivity of construction projects over the years in Makkah. The boom in customer demand for projects is putting pressure on the construction industry and the industry is struggling to meet the increasing demand for its services. Rework is another effect of the adoption of unskilled labour force in the construction industry, due to poor quality of work and low productivity. Lack of skills can lead to rework as a result of inadequate supervisors, ratios of supervisors, low level of skilled workers, unclear instructions from supervisors, non-compliance with set specifications, and poor coordination of resources. Foundation failure, which is common in start-up construction companies, is another consequence of skills shortages.
The stakeholders in the construction industry need to pay greater attention to this in order to boost performance and guarantee the completion of construction projects. Evaluation of the issues affecting the shortage of skilled laboures for sustainable building has been identified in this article. The results of this study will assist researchers better understand the complex problems affecting construction projects in Makkah city as well as the construction community in Makkah and throughout Saudi Arabia.
This study presented the significant factors influencing shortage of skilled labours in Makkah construction industry from building and construction practitioners perceptive that have been working for more than 1 3 15 years in Makkah. Although, some of the significant factors follow the same trend as those found by other researches on the literature, new attributes are emerged in this study including delay in salary payment; low wages structure; and lack of motivation system. This is aligned with the perceived low productivity of construction sector in Makkah.
This study offers some recommendations for professionals and academics researching skilled labuors in the construction sector. The first implication is that the performance of building projects may be impacted by a lack of skilled labour. The performance of the construction project has been favourably impacted by the skilled labour scarcity, as evidenced by the findings of our proposed framework. This study backs up the assertion that having access to trained labour is crucial to the success of building projects. The second implication is that human capital and project-related factors might have an impact on the availability of skilled workers in the construction sector. Both causes are equally capable of contributing to a lack of trained workers in the construction sector. Therefore, while developing qualified human resources for the construction business, these issues should receive careful consideration.
Accordingly, the following recommendations were proposed to minimize shortage of skilled labours in construction projects of Makkah: 1. Construction organisations should resolve delay in salary payment by efficiently controlling project resources. 2. Construction organisations should secure sufficient cash flow throughout the project lifecycle. 3. Wages should be distributed fairly based on skills and experience and not based on nationality. 4. Construction organisations should resolve motivation issues by giving some incentives, reward or bonus to workers, and also to allow overtime motivation to improve workers financial status. 5. The contractor must manage its finances and cash flow planning by utilizing phasing effectively and efficiently to avoid any disruption to the project's financial progress. 6. The customer must make an advance payment to the contractor on time to enable the contractor to finance the project. 7. An appropriate coordination system should be established between the project parties to increase project performance. 8. The contractor should establish a dedicated team to plan and monitor the progress of the work on a daily basis and the pending issues.
9. It is essential to establish appropriate formal communication channels between all parties to the project throughout the project life cycle. 10. The contractor must employ the competencies and professionalism of his organization in order to prevent the project from facing construction delays. 11. The contractor must employ a sufficient number of skilled workers and motivate them to improve the productivity of construction activities. 12. The production of the design documents must be done on time, otherwise the delay in the production of the design document will affect the slow implementation of the site.

Consent for publication
The participants has been asked and they all agreed in the statement "I understand the general purposes, risks and methods of this research. I consent to participate in the research project and the following has been explained to me: the research may not be of direct benefit to me. My participation is completely voluntary. " Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/.