DEVELOPMENT OF APPROPRIATE LABOUR CONSTANTS FOR BUILDING PROCESSES

Author: Ngwu Chukwuemeka
Department: Building
Affiliation: Nnamdi Azikiwe University Awka

Labour is one of the key components of unit rates for bill of quantities items. The major challenge facing estimators when pricing bills of quantities for tendering is their inability to quickly lay hands on proper information about labour thereby resulting in high variability of tender prices among builders bidding for building contracts in Nigeria. These information are the standards, usually given as constants in the form of time necessary for the manual completion of a defined quantity of work – standard time (st), or in the form of unit output – standard output (sop) for a specified working time. The aim of the study is to improve the reliability of tendering among contractors and assist in effective project planning and control. Consequently, a survey was carried out in six organized building sites two each in Anambra, Ebonyi and Enugu States of Nigeria with a view to developing appropriate labour constants for building processes (concrete work and block work). Research questions and corresponding hypotheses were postulated on the factors that cause low productivity of tradesmen on site, the degree of effect of these causes and whether there are significant differences between the existing labour constants and the evolved ones. The study adopted both field survey and work study technique designs using different data collection instruments, namely structured questionnaires, personal interviews, observations and measurements. A total of 250 questionnaires were distributed to the three categories of tradesmen, namely carpenters, masons and iron benders, out of which 215 were properly completed returned and used for the analysis. The sites were selected using purposive/judgmental sampling technique. Data obtained from the questionnaires were subjected to analysis using the following statistical tools: Frequency table and percentages. Mean score index, Relative importance index, Chi-square, Cramer’s V (V) and One-way analysis of variance. Work study was used to develop appropriate labour constants, and this involved full time scale study of each operation that make up the activity for each process by observing and recording using stopwatches the start and finish durations of each operation per shift for different cycles as well as measuring the quantity of work carried out by each gang for eight – hour working day. A three-time estimate using the formula for most probable time to complete each operation that make up an activity relative to the quantity of work performed, Regression analysis and Students tstatistic were used for the analysis. The results show that welfare facilities and design documentation most significantly affect the productivity of tradesmen on site and the developed labour constants are more realistic and appropriate for pricing than the claimed outputs by the tradesmen in the study area. In the light of the above findings, it is recommended that builders should provide adequate and decent welfare facilities. Building projects should be conceived by designers to avoid design complexity and design changes which could result to rework, and therefore avoid delay. The developed labour constants in this research are strongly recommended as veritable tools for realistic pricing. This will reduce the level of variability in tender sum among contending bidders. It will further assist in effective project planning and control through realistic determination of optimal labour force in the execution of building projects.

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