# Assessing and Priorities Delay Factors of Prefabricated Concrete Building Projects in China
## 2 Schedule Management in Prefabricated Building Projects
### Identification of Construction Delay Factors  
To explore strategies for minimising schedule delay risks, it is important to identify the main delay factors in prefabricated building projects, prioritise key factors, and quantify their relationships. Therefore, a simple searching procedure is implemented by searching delay-factor-related and schedule-risk-related papers within the high-impact construction journals suggested by [PERSON] [34]. The literature limited to the last ten years (2009-2018) is then summarised in Table 1 and used to identify various delay factors. Once the delay factors are identified, elements irrelevant to prefabricated concrete building projects and rarely-occurring causes are excluded in this research through an expert interview. Table 2 displays the key factors affecting the schedule of prefabricated concrete buildings from the aspects of construction techniques, workforce, resources, machinery, clients, contractors, and external conditions. 1. Construction Techniques: Although off-site construction significantly reduces the on-site construction workload, it is difficult to cope with various prefabricated components. The components are also relatively large and heavy, which requires sufficient site space, and the appropriate schedule control for hoisting and installation. In addition, high-precision installation techniques are crucial for prefabricated construction, especially complicated connection processes [16]. Thus, technique-related risk factors, including inappropriate site management and low-level installation technologies, inevitably affect the project progress of prefabricated buildings. 2. Workforce: There is less workforce requirement in prefabricated construction, compared with traditional on-site construction. However, the current prefabricated construction process is not technologically advanced and relies on intensive labour, and the labour requires machine-oriented skills both on site and in the manufacturing process. Inadequate worker experience and poor performance have significant impacts on project progress. 3. Resources: Material shortage is a potential source of construction delay. The major cause of material shortage is that demand exceeds supply. Offsite prefabricated systems vary depending on the sizes of prefabricated components, which affect the need for on-site construction. Another cause of material shortage could be damage to stored components. 4. Machinery: Lack or unavailability of equipment is a significant factor that contributes to delays. In the construction stage, some contractors may experience the lack of machinery to produce work because of high cost and equipment failure. 5. Contractors: Time estimates aim to manage and structure projects. Ineffective planning and scheduling by contractors is another key driver in delaying projects. Poor site management and supervision also contribute to project delays. Large prefabricated sections may require heavy-duty cranes as well as precision measurement and handling to place in position.