Overdesign of Villa Structures in Oman

Abstract

Residential projects represent the largest section of the construction industry in Oman. It is widely claimed that designers in Oman tend to unnecessarily overdesign structures, thereby aggravating construction costs. The aim of this research was to investigate the existence and extent of structural overdesign through the investigation of 31 villas which were approved by Muscat Municipality between 2000–2010. The specified villas were structurally redesigned based on the British Code of Practice using the same geometry and material strengths recorded in the drawings. The required reinforcement resulting from the redesign work was compared with the provided reinforcement as per the drawings. The results showed clear cases of extra reinforcement in almost all villas. The difference between required and provided reinforcements in the villas ranged from 2.3– 104.8%, with an average of 48.5% and a standard deviation of 24.0. The required and provided weights of reinforcement per square meter of the built-up area ranged from 25.7–71 and 40.9–87.9 kg/m2, respectively. The largest differences between the required and provided reinforcement were in the slabs, followed by the footings. A field survey of consultants and municipality engineers indicated that the most notable reasons for overdesign are the absence of authorized agents specialized in reviewing structural design, a lack of an engineering licensing system in Oman, and the phenomenon of experienced engineers leaving design offices for better paying jobs elsewhere. Finally, the cost implication of overdesign is minor compared to the overall cost of building.