The sustainability and success of the construction industry depends greatly on the level of accuracy in project estimates. The consequences of adopting inaccurate estimates are quite enormous and overwhelming. This research aims at using work study approach to empirically establish labour outputs of some selected trades for the Nigerian construction industry with the view of increasing the accuracy of construction cost estimates. A total of 15 construction sites were sampled within Zaria and Kaduna town. Physical observations and measurement of work outputs on block work, plastering/rendering and excavations were conducted through work study approach, particularly work measurement. Data collected were subjected to statistical analysis using both the descriptive and inferential data analysis techniques. The inferential tools made use of T-test statistics to assess and examine the influence of the various labour productivity factors on the outputs of the workers observed. The results of the analysis carried out established general average output values per day of; 10.68m2 30.85m2 and 19.04m3 for block laying, plastering/rendering and excavating trenches i.e. 1.50m deep respectively. However, The test of difference conducted in order to analyze and investigate the extent of influence of the productivity factors discovered a consistent significant difference in output of workers as the period of observation and the level and style of payment is varied. Also age as a productivity factor affected only the outputs of trench diggers excavating trenches n.e 1.50m deep. Similarly, even though differences existed between outputs in block laying and plastering operations, the tests conducted confirmed that they were quite insignificant. The level and length of experience of tradesmen observed had a tremendous effect on their outputs in block laying and plastering operations. Nonetheless, that did not affected workers in trench excavations operations. The additional qualifications obtained by the tradesmen in addition to their apprenticeship qualifications only affected the output of plasterers and was virtually insignificant to the other tradesmen in their trades operations.
The research concluded by recommending the outputs established to Contractors so as to exploit the output figures extracted according to productivity factors in order to optimize the productivity of their workers and profitability.