EFFECTS OF ELECTRICAL MATERIALS AND INSTALLATION COST ON THE TOTAL CONTRACT SUM OF RESIDENTIAL BUILDINGS IN ABUJA

Abstract

The non-availability of working drawing for electrical services for most residential buildings have led to variations and false claims by the contractors. In addition, this has led to inaccuracy in cost estimates due to the technicality and complexity involved in the interpretation of electrical working drawings and specifications. Hence, the aim of this study was to assess the implication of electrical materials and installation cost on total contract sum in selected building types in Abuja. The methodology involved a structured questionnaire administered to 384 industry professionals (electrical engineers, project managers, quantity surveyors, electrical technicians, and procurement managers). Using a random sampling technique, 197 responses was recorded which represents 51.3% return rate. The study thus used multiple regression for cost modelling of total contact sum using piping, cable, fitting and installation costs for two, three, and four bedroom apartments respectively. Findings revealed that there exists a positive and moderate relationship between the independent variables (piping, cable, fitting and installation costs) and the dependent variable (total contract sum). Additionally, the cost estimation models developed for the selected building types (two, three, and four bedroom apartments) are CS = 0.584 + 0.215 PC + 0.344CC + 0.275 FC + 0.166IC, CS = 0.597 + 0.206 PC + 0.389CC + 0.237FC + 0.165IC, and CS = 0.588 + 0.202PC + 0.402CC + 0.229FC + 0.165IC respectively. The study concluded that the contract technique mostly adopted in electrical project is the lump Sum (or fixed price) contract technique. The major factors affecting the total contract sum as a result of electrical material and installation costs in order of importance according to findings are design error, supplier manipulation, change order, government policies and cost of labour with mean values 4.57, 4.40, 4.38, 4.23 and 4.20 respectively. Hence, the study recommends that electrical contract sum must be determined and calculated accurately and correctly using the required components from correct electrical/architectural working drawings, and the appropriate contract technique must be selected.