Number of researches and articles have been studied on causes of delay in construction industry. The outcome of these studies have been reviewed for this particular research. Distributed the delay causes into various causing groups (consultant, owner, contractor, labor, material, equipment, project and external related groups), and the major causes of delay were rated into very high, high, medium, low and very low delay related causes. Mohamed and Tarek et al 01.
The delay factors was divided into three main groups.
1-The input factors group: was described as resources required for the project as labour, material, equipment.
2-The internal environment group: the participants in the project including-employers, consultants and contractors.
3-The unpredictable factors group: climate changes, changing in the policy of government and other casual occasions. Michal and Angieszka et al 03.
The main delay causing factors was divided into nine causing factors (contractor related, lake of labour, external factors, material deficiency, design errors, owner related, technology restrictions, consultant related and project related). Out of these delay causes or factors the technology restrictions factor was the most important and causative factor of delay. Samad and Mohamed et al 09. Eighty three factors of delay were found, and also the factors were combined into nine groups, the importance index was used to rank and rate important causes or factors of delay, and also the top ten major delay causes in Afghanistan were gathered as follows (security, corruption, unexperienced contractor technical staff, poor site management, poor supervision by the contractor, ineffectual planning and scheduling by the contractor, delay in the invoices of project by the employer or government, difficulties in project financing by the contractor and the final one type of project bidding or award). Ghulam and Kassim et al 04. Found that the Indonesian construction industry is not influenced only by labor related aspects, but there are some more significant factors (equipment, material, construction methods, site management and non-professional management), the delay causes were categorized into six different groups (people, non-professional management, design and documentation, material, execution and external factors. Keith et al 05. The most significant effects of delay were discussed (time overrun, cost overrun, litigation, disputes, lawsuits, project abandonment, bankruptcy, arbitrations. And a theoretical outline of delay factors were determined as follows (client/sponsor/owners/projects team, consultants/design engineers/contractors/sub-contractors, materials, government authorities, socio-economic aspects and others). Ghais et al 06. From this particular study gathered the delay in honouring payment certificate was the most causative and important factor of delay in construction projects by the contractor, and also this study showed that the most significant factors of delay are (time overrun, cost overrun, loss of reputation, loss of productivity, efficiency, rescheduling of the project and claim and litigation). Benjamin et al 07. It was found that (inflation, inadequate financing by the owner, poor feasibility study of the project and extreme scope changes are the key delay factors in construction projects at Middle East, and analyzed that the inadequate financing occurs due to inflation and most of the times due to poor feasibility study. The risk factors in civil engineering projects in Middle East were determined as follows (oil price instability, currency rate instability, geo-political issues and risks, labor non-availability, form of contract, non-accurate cost estimations, inflation and delay factors or causes related scope changes). Maryam et al 10. At least 42 delay causes were found and existing in a questionnaire survey. 179 experts was given their response and was analyzed by Importance Index, Spearman’s Rank Correlation, T-Test, Risk Mapping and factor Analysis. And the most major delay factor in was the low productivity of works (57.86%). The study analysis indicated that the most causing delay factors or causes in Qatar construction industry were (low productivity of worker, delay in decision making, delays related to sub-contractors, changes in project by owner and unqualified workforce. And the delay causes for the rest of the word were also given as follows (delay in decision making by the owner, low productivity of the workers, poor site management, delays related to sub-contractors works and complications in planning and scheduling by contractor. Mahanad et al 11. The delay was defined as surpassing the completion of construction project by the time duration specified in the contract, or surpassing the time duration on which both the parties agreed to the delivery of the particular project. In Indian construction industry mostly delays occurs due to poor cooperation of the participants (owner, contractor, consultant and others). The eight delay factors were found with their eight effects.
8 delay factors: owner, contractor, designer, worker, material, equipment, construction and external factors.
8 delay effects: time overrun, cost overrun, loss of productivity of owner, damage to the reputation of the company, delay in payment by owner, the participants of the project are in disputes, exit of the project, reduction in the market value. Mr.Karthik et al 12. Almost 51 delay factors were found, the questionnaire survey was conducted in order to find the most important delay factors or causes. The top ten ranked delay factors accorded to the project participants in Turkish construction industry are (termination of the project by owner, delays in progress payment by owner, impractical project duration, lake of decision making process by owner, inadequate planning of the project, difficulties in financing by contractor during construction, shortage of labor, slowness in the delivery of materials, difficulties in obtaining permits of municipality, change in design by owner). Mehmet et al 13. The mostly important factors of delay in construction projects were analyzed and the relationship between delay factors and plant and equipment management was identified and cleared, for effective and better plant and equipment management few studies were recommended, in order for future minimization of delay in construction industry a plan for plant and equipment management was recommended. Sri Nuwan et al 14. The delays of schedule which occurs mostly in projects were categorized into non-excusable, non-compensable excusable, compensable excusable and concurrent delays. Aside with that the questionnaire survey and structured interviews were conducted to collect the opinions of consulting, construction firms, financing institutions and implementing agencies, the structure of interview questions were constructed according to the data collected from literature review and was identified those challenges that financiers, consultants, contractors and implementing agencies are facing with them in implementing road construction projects in Zambia. The effects or belongings of cost escalation which causes delay of project’s schedule were given as follows (poor quality of the end product, project schedule extension, litigation, project abandonment and cost overruns. Found that bad or extreme changes in weather due to very heavy and hard rains which results floods is the number one and most important delay factor for cost and schedule escalations, and was followed by changings in scope, mitigation and site protection. Chabota et al 15. Delay of projects have been a global phenomenon and are accompanying by time and cost overruns, can be prevented while their causes have found and identified. In this research code-related delay was discussed as the most critical factor and was followed by design related delays, construction related delays and so an. These most significant factors of delay in Californian construction industry was ranked as follows: 1- change order (3.81), 2- drawing changes (3.76), 3- partial documents, 4- inspections (3.40), 5- specifications changes (3.37), 6- decisions while project is in the development stage (3.350, 7- plant drawing approval (3.23). Syed and salman et al 16.The focus of the study was on large building projects in Bangladesh, the three main and major parties of projects were asked to find the most significant delay factors of projects, 79 important delay factors were found in building projects, the parties were agreed that among all theses 79 factors inexperience project managers, fund restrictions from owner, lowest bidder selection in bidding process, site constraints, inappropriate planning and scheduling, contractor’s extreme work load, lake of skilled workers, unsuitable cooperation among project team, problems of cash flow during construction of project by contractor, sudden escalation of resources prices, etc. Muhammad et al 17. The delay factors in the complete results were separated into eight different groups: 1- client, 2- contractor, 3- consultant, 4- labor, 5- contract, 6- external factors, 7- the contractual relationship, 8- material and equipment. The most important delay factors identified by survey, literature review and the overall results are as follows: 1- weakness in financing by owner, 2- unexperienced contractors, 3- non-payment by owner, 4- the poor qualification of the technical staff of the contractor, 5- and mistakes in soil investigations. And the lake of financing by owner was returned as the main delay causing factor, the delay effects were mostly same to the effects discussed almost in all papers. Aymen et al 18. The delay causes or factors which effects time, cost and quality were discussed and studied to find those factors which mostly impact the objective and out puts of the projects. The delay causes were ranked by importance index method and flooding was stated at the top of those casual factors. Anuradha et al 19. The delay causes were classified into numerous groups, in order those delay groups were ranked as well, a number of most important delay factors were listed as (schedule overrun, cost overrun, disputes, arbitration, total abandonment of projects and litigations). Ghanim et al 20. The main delay factors were identified, from the overall result of questionnaire slow decision making and unexperienced project staff, low performance of sub-contractors, delay in material delivery to site, design changes were considered as most important causing factors of time overrun in construction industry in North Cyprus. The focus of the research was on identifying of the most important delay causes and few case studies were studied and analyzed for this purpose. Seyed et al 21. Apart of the questionnaire survey numerous case studies were analyzed and discussed and the time and cost overrun factors and their effects were identified. Disappointment and arbitration were at the top of delay factors in civil engineering, found that the average projects in their duration is effected by delay, and was recommended if the project team owner, contractor and consultant take their responsibility on time and coordinate as a team delays can be minimized or prevented. Symon et al 22. 17 client related delay causes were found, with the average Index of Importance (47.05), 20 contractor related delay causes were found, with the average Index of Importance (47.40), 7 consultant related delay causes were find, with the average Index of Importance (44.13), 4 external related delay causes were also found, with the average Index of Importance (38.65). The most important and significant delay causes were ranked and inadequate supervision and management by the contractor was ranked at the top of the ranking list. Dr.Ashraf et al 23. The two most important delay causes were both related to client and management. 1- Weakness of key project participants. 2- Actions and omissions of the participants of the project. Hence, poor management and coordination of project team was considered as the source of project delay. Alfred et al 24. The top ten most important delay causes were found and listed as: ineffective planning and scheduling, errors and delay in producing of the design papers, delay in progress out flow, less experience of owner in construction, delay in delivery of materials, shortage of labor, lake of design experts, poor qualification of contractor, changing of sub-contractors frequently, delay in putting to services. Anil et al 25. 15 causes of delay were found and they were ranked according to the Mean Index Score, the causes includes: poor financing, changing in drawing, poor communication among the parties involved in the projects, inadequate information by consultants, slow decision making, inexperience project team, mistakes in contract documents, non-availability of equipment and failure, mistakes during construction phase, bad weather, increase in prices of building materials, inappropriate organizational structure and labor strikes. And the most major delay effects were: overrun of time, cost overrun and so on. The data collected from experts was indicating that the client having the highest percentage (51.1%) of causes of delay, followed by the contractors having (35.5%) then the consultants with the least percentage of (13.3%) causes of delay in construction industry. Owolabi et al 26. The delay causes were ranked accordingly through different ranking methods (Frequency Index, Severity Index and Importance weight). Also the delay causes were categorized into four (contractor, owner, consultants and external) distinguish groups. The most significant delay causes were given as low skilled labor and increase in price of materials. Shebab et al 27. The delay types were categorized into four different groups (critical or non-critical, excusable or non-excusable, compensable or non-compensable and concurrent delays), apart with that the delay causes were categorized under each type of delay. Overall 83 delay factors were found. Leena et al 28. 72 delay causes were found and were distributed into six categories (consultants, client, contractors, projects, resources and external) related. It was found that among the top ten delay factors five were related to resources, two were related to contractor, two were related to external factors and one was client related delay factor. The top ten delay factors in Malawi construction industry were indicated in this particular paper as: fuel shortage, deficient contractor cash flow, delay in progress payment by client, shortage of foreign currency for importation of materials and equipment from other countries, deficient equipment, delay in displacing equipment, shortage and lake of construction materials, delay in the payment of compensation to land owners, lack of technical staff and delay in mobilization to site. M J Kamanga et al 29. The delay of construction projects were classified into two (external and internal) groups. Internal group included: client, contractor and consultants. External group included: Act of God, weather conditions, government…etc. found that construction projects in Malaysian construction industry are delaying with average (20.102%) of time overrun percentage. Overall 30 causes of delay were found. Mohamed Babikir 30. The major delay factors in Norwegian construction industry were given: poor planning and scheduling, slow decision making processes, resources shortage, poor communication and coordination among the parties, slow quality inspection process of the completed work by the project team, changes in design during construction, client lake of commitment, office issues, delay in design and user issues. Youcef et al 31. At all 11 delay factors were discussed the most significant factor which cause delay in construction projects were given as: legal obstacles and permits, defective provision of design details and specification, slow decision making process and change in order from the client’s side. Aleksander et al 32. Overall 39 delay causes were studied, the top ten delay factors were given as follows: slow decision making process, poor site management and supervision by contractor, delays by the cub-contractor, shortage of material, rework due to errors, low productivity level of labor, payment delay to contractor, delay in obtaining work permits and the last one delay in commissioning. Aedwin et al 33.