Developing and implementing an empirical system for scoring buildability of designs in the Hong Kong construction industry

Abstract

In view of the Construction Industry Review Committee's report which highlighted the unsatisfactory buildability situation in the Hong Kong construction industry, this study is aimed at improving buildability by providing a yardstick for measuring and appraising the buildability of different building designs. In this study, buildability is defined as "the extent to which a building design facilitates efficient use of construction resources and enhances the ease and safety of construction on site whilst the client's requirements are met". The research objectives are (i) to identify the most effective approaches for improving buildability; (ii) to formulate a scoring system to evaluate the buildability of different design components; (iii) to devise a Buildability Assessment Model (BAM) based on the scoring system for use in Hong Kong; (iv) to validate the BAM; and (v) to develop strategies for improving buildability using the BAM. Amongst alternative means as reported in the literature, the quantifying assessment of designs was found to be the most practical and successful approach in improving buildability. Upon evaluation of contemporary studies in quantifying design buildability, the Buildable Design Appraisal System (BDAS) in Singapore has been demonstrated as being suitable for adaptation in Hong Kong. The proposed Buildability Assessment Model (BAM) has been established through carrying out a series of structured interviews and questionnaire surveys. The techniques of Factor Analysis, Analytical Hierarchy Process and Relative Importance Indices were used for data analysis. The BAM can be used to assess buildability of designs by focusing on 6 design components, namely: (i) Structural Systems; (ii) Slab Systems; (iii) Envelope Systems; (iv) Roof Systems; (v) Other Buildable Features (including Internal Wall Systems, Finishing Systems, Building Services Aspects and Building Features); and (iv) Site Specific Factors. For other design features which have not been covered by the BAM, an Open Score up to 10% maximum is given. Each design component contributes a sub-score of buildability. The calculation of the sub-scores depends on the physical coverage of the design components, the Buildability Indices representing the relative buildability of various design elements, as well as the Buildability Weightings representing the relative importance weightings amongst different design components. Summation of all sub-scores of the relevant design components and the Open Score gives the overall Buildability Score for the building design. Upon establishment of the BAM, the validation process has been undertaken and refinement made to further reinforce that the Model is largely accurate and representative in reflecting design buildability. The proposed BAM contributes to existing knowledge by providing a yardstick for buildability comparison amongst different designs, thereby serving as an incentive for buildability enhancement in Hong Kong. Eventually, recommendations have been made to enhance the implementation of the BAM such that in the long run, an increase in productivity and saving in manpower requirements on building sites can be achieved.