A STUDY ON CLIENT'S DECISION-MAKING IN CONSTRUCTION PHASE OF BUILDING PROJECTS IN JAPAN

Abstract

Building projects need many decision-making, and clients cooperate to decide with architects, supervisors, general contractors and other consultants in projects. Especially in Japan, because the project members trust each other and the ability of Japanese general contractors is excellent, clients often make a decision in construction phase. However, the laws in Japan don't define client's decision in construction phase clearly, and that often makes some kinds of risk (e.g., design change, delay of projects, and high cost). This paper aims to clarify factors and influence of client's decision-making in construction phase in Japan. There are three main laws related construction projects in Japan, Building Standards Act, Act on Architects and Building Engineers, and Construction Business Act. In addition, there are several standard specifications of construction work and standard forms of contract in Japan. These three laws and some standards define client's decision-making as follows. [1] if they find some mistakes in drawings in construction phase, clients must make architects correct it. [2] by agreement with the project member, clients can change drawings in construction phase. [3] if the design change affects structure, clients must perform structural calculation and obtain the application of building confirmation. [4] In case that it is reasonable to select in construction phase such as color, material and equipment, clients can select them in construction phase after clarifying in drawings. Therefore, we took the questionnaire about current status of client's decision-making involved in reinforcement work, steel work, exterior work, and equipment work. Questionnaire was an open-ended question method and composed of three questions as below. [1] what kind of client's decision-making is there? [2] what factors of decision-making are there? [3] what influence of decision-making is there? The sample was restricted to people in construction project and the respondents were belonged to clients, developers, architects, and general contractors. A total of 78 questionnaires were distributed by e-mail and 14 samples were collected. The results of survey revealed the difference of client's behavior between 4 works. In reinforcement work and steel work, clients do not decide and instruct the number of reinforcement and performance of a steel member directly. However, clients affect these works indirectly. In design phase, sometimes, clients do not decide certain use of space because they want to follow a trend or they have not decided tenant yet. In this case, clients decide these things in construction phase and that makes change the position of partition and piping sleeve in reinforcement work and steel work. In exterior work, it is reasonable to decide color and material of exterior in construction phase because clients cannot judge from only drawings whether the design is good. General contractors make mock-up for clients to check the design and clients decide or change the design detail directly. In equipment work, clients affect it in two ways. In case that it is reasonable to decide it in construction phase, clients decide the position, number, and performance of equipment directly. On other hand, in the case that clients decide use of space in construction phase, the use and size of the room determine the required position, number and performance of equipment. Finally, in order to analyze factors of client's decision-making, we applied the fishbone diagram analysis. Fishbone diagram is the tool for identifying the root causes of problem, which was “Client's decision-making in construction phase” in this paper. This diagram has 3 main causes (project member, building type, building element) and 42 secondary causes. In addition, it was modeled how client's decision-making in construction phase affects the post-process of four works.