Cutting construction wastes by prefabrication

Abstract

Construction wastes have become the major source of solid wastes in Hong Kong. Thousands of tonnes of solid wastes are produced every year from construction and demolition activities. Increasing generation of these wastes has caused significant impacts on the environment and aroused growing public concerns. Therefore, the minimization of construction wastes has become a pressing issue. This paper aims to: i) revealing the status of construction wastes; ii) investigating the effectiveness of prefabrication in terms of waste reduction in replacing traditional wet-trade practices; iii) examining the factors that help minimize construction wastes by the adoption of prefabrication; and iv) exploring the current waste reduction situations after adoption of prefabrication by comparing with in-situ construction. It investigates wastes generated from various wet-trade construction activities such as in-situ concreting, timber formwork, bricklaying, plastering, screeding, tiling, rebar fixing and bamboo scaffolding. Six major reasons for the excessive construction wastage are known to be: i) cutting; ii) over ordering; iii) damaging during transportation; iv) losing during installation; v) poor workmanship; and vi) change of design. From the findings of a structured interview survey of thirty-one construction practitioners, "timber formwork" is found to be having the greatest potential for cutting scrap, and wastes from "poor workmanship" can be greatly reduced by adopting prefabrication in construction. Furthermore, after the adoption of prefabrication, wastage generation can be greatly reduced in various wet-trade activities including concreting, rebar fixing, bricklaying, drywall, plastering, screeding and tiling. Especially in plastering, the waste reduction can be reduced by 100%. It is concluded that prefabrication of building components is one of the effective technologies of waste minimization.