A comparative study of user perceptions on prescriptive specifications versus performance-based specifications

Nearly every construction project has its specifications written in either the prescriptive format or the performance-based format, or a mixture of both. The recent proliferation of specialist works and the popularity of the Design and Build procurement method have given rise to an increased use of performance specifications. Whilst prescriptive specifications are characterised by detailed descriptions of material and workmanship requirements, performance specifications lay down the desired end results and verification methods. It is often said that the latter allows flexibility and encourages innovations in the use of materials, systems and methods. Yet, performance specifications are not without their problems. Commonly cited complaints raise questions on the practicality of some targets, as well as the lack of objective criteria for testing certain results. Substantiating the achievement of desired results becomes problematic for many contractors. A recent survey carried out in both Hong Kong and Singapore explored the perceptions of users on both types of specifications. Clients, consultants and contractors have given their ratings and opinions on the attributes, usefulness and limitations of performance specifications. The types of work currently being specified by performance in the two cities were also surveyed. Some interesting comparisons on the use of prescriptive and performance specifications have been made between the two cities and they are correlated with the respective contextual backgrounds, which are largely similar yet with distinguishable features.