BUILDABILITY ASSESSMENT MODEL FOR BUILDING CONSTRUCTION IN CAMBODIA

Abstract

Buildability refers to the integration of construction knowledge during the design stage to enhance the ease of construction while meeting all requirements of the owner/client. Lack of buildability in designs could result in design reworks, low site productivity, costs increase, and contract changes. Due to differences in site conditions, construction techniques, materials, equipment and experiences available, the buildability factors vary from countries to countries. Therefore, a model to comprehensively evaluate the buildability of building designs based on localized buildability factors at early phase of design is needed. The research is divided into two main parts. The first part aims to evaluate the importance level of buildability factors of building designs in Cambodia. The questionnaires using five-point Likert scale were distributed to project managers and site engineers of contractors in Cambodia. The analysis of One-sample t-test showed that there were 12 important factors that affected the buildability. The top 5 important factors associated with buildability were: (1) standardization of designs; (2) completion of design documents; (3) clarity of specifications; (4) requirement of labor skill; and (5) design to suit site conditions. The ranking of the factors and factor categories provides useful information for designers to improve buildability of their designs. The important factors of this research were then used for the development of buildability assessment model for building construction projects in Cambodia. The second part focuses on the development process of a model to assess the buildability of building design. The model was based on an Analytic Hierarchy Process (AHP) model. This part of research was divided into two main steps. First, structured questionnaires were conducted with mid- and high-rise building contractors to obtain the weights of buildability factors. Their opinions were aggregated by the geometric mean on judgments in AHP group decision. Then the subcriteria to evaluate the buildability factors and the current practices of designs were collected by cross-case analysis of structured interviews. Design for available resources was found to be the most important category of buildability followed by design to support site layout and design documents. The most important buildability factor under each category was design to support transportation of materials and labors, requirement of labor skill, and completion of design documents. This model was validated by applying 11 building projects in Cambodia. This model can serve as a framework to assess the buildability of a building design by the design team so that necessary improvements can be made before construction.