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Abstract
This study attempted to develop a knowledge-based decision support system, called ‘Knowledge-based Decision support System for roofing Material selection and cost eStimating’ (KDSMS), to facilitate the selection of optimal material for different roof sub elements. The aim of the decision support system is to provide a tool for the architects, quantity surveyors or self house builder to select optimal materials for different roof sub elements and also to estimate the conceptual cost for the roof element in the early stage of design.
The developed system consists of a database and a knowledge base. The former is used to store different types of roofing materials with attribute values. The later is used to hold qualitative and quantitative knowledge which were collected from domain experts and other technical literatures such as building regulations, price guide book and product catalogues. The developed system employed the TOPSIS (Technique of ranking Preferences by Similarity to the Ideal Solution) multiple criteria decision making technique to solve the material selection and optimisation problem.
The developed system was evaluated by using the pitched roof projects data collected from human experts from the construction industry in Northern Ireland through a questionnaire survey. Using the Student t-test statistical analysis, the evaluation results showed that the system has a very good predictive ability for estimating the roofing element cost at early design stage. It also proved very efficient in material selection capability. In addition, the results show some possibility of cost reduction when optimal materials are selected, something that would not be obvious when manual selection is carried out.