Advantages of Prefabrication Construction in Comparison with Conventional Construction

Recent innovations in the construction process should be noticed in the total context of the technological development of human societies over time. There is a general impression that the extensive advantages in productivity and quality, reached in manufacturing industries, have not been matched by similar progress in building construction. This paper reflects this deep belief that a significant order to this problem can be attained only with prefabrication, industrialization and automation replacing manual labor in all phases of the construction process. Prefabrication and industrialized building systems are the processes of an investment in construction equipment, facilities, and technology with the purpose of increasing output, saving manual labor, and improving quality. These building systems increase productivity and improved the performance and quality of the construction components. Moreover, they are a set of interrelated components that act together to reach the defined performance of a building. In a wider sense they also include several technological and managerial methods for the producing and assembling of their components for this intention. Many of possible construction components are prefabricated offsite at a central facility where specialized equipment and organization can be established for this purpose. The several building works are incorporated into large prefabricated assemblies with minimum erection, jointing and finishing work onsite. Materials and component handling onsite are widely mechanized and in concrete work, large standard steel forms, ready-mixed concrete, and concrete pumps are used. Design, production, and erection onsite are strongly interrelated and must be viewed as parts of an integrated process which has to be planned and coordinated accordingly. Automation is introduced into the prefabrication building systems in realization process in order to reduce human involvement and improve quality in design, production, and construction onsite. In this paper, the possibility of using prefabricated construction systems in building industry is discussed. These argued subjects are: • Analyzing of Demolition Management in Construction, • Analyzing of Benefits and Disadvantages of Prefabrication Building Systems and Applying these Construction Methods in Building Industry, • Presenting an Effective Patterns in Using Prefabrication in Construction of Various Buildings, • Economic Analysis of Applying Prefabrication Methods in Building Industry. A lot of prefabricated components are vastly applied in construction. They have potential to reduce waste production and minimize negative environmental impacts of buildings. In order to compare advantages, disadvantages, barriers and development of prefabrication in building sites, a questionnaire was presented to proper and qualified building constructors in Tehran city, Pardis and Parand new towns. Required data are collected and extracted from completed questionnaires and in order to simplify the analysis of data, findings are categorized in tables. Finally, advantages, disadvantages and future developments of applications of prefabrication are presented and appropriation of these building systems is analyzed for different types of construction projects according to the categorized and meaningful tables. It can be inferred from the findings that various advantages of prefabrication have different values. “Supervision of increasing the quality of prefabricated components” item has the highest value and “better and improved design” and “decreased total costs” are the next main items. In the other hand, some disadvantages of prefabrication systems are noticed, too. Findings show that prefabricated buildings are not flexible or adaptable to future changes. In most cases, after compilation of prefabricated buildings, end-users can’t modify them easily. Thus, “rigidity to change” is the main disadvantage of prefabrication. Some findings related to future developments demonstrate that prefabrication construction methods should be considered in preliminary design process in order to achieve the upper standardization level. “Upgrading construction techniques” and “fitting to the future projects” are the second significant items supporting the future improvements. In addition, feasibility of applying prefabrication in building projects was discussed. Five basic items (sub-structure, structure, exterior construction, interior construction and building installation) were analyzed focusing on main projects, mass housing, personal housing and commercial projects. It can be shown that conventional construction methods are suitable for foundation, sub-structure and non-standard construction. Prefabricated components are preferred to steel structural frames, facades, concrete roofs, dry-wall systems. Many of prefabricated components are load-bearing elements and development of lightweight prefabricated components should be considered in order to reduce the use of raw materials and shipment. In addition to the above items, nowadays large quantities of waste are generated in building industry while most of its significant environmental aspects remain unnoticed. Conventional systems seem to be unable to provide satisfactory results in building industry. Based on the results, by using prefabrication methods, construction waste could be reduced to half and the most reduction will be in wall finishing and coating phase. Also, using standard and regular designs for buildings will be helpful. Moreover, through mechanization, using recycled or recyclable materials and industrial assembly of prefabricated components, the costs could be reduced.