The source and nature of output constants used for preparation of construction estimates should be accurate and reliable for the client to have confidence on the prepared estimates. This research is focused on using time study approach to empirically determine the outputs of block laying work items inconstruction industry. The study reviewed BESMM3 and surveyed possible block work items in construction sites. Ten work items were selected from the identified block work items in BESMM3 and construction sites for Physical observations and output measurement. A total of 105 sites were observed in F.C.T., Abuja and Nasarawa state. Data collected were subjected to statistical analysis using both the descriptive and inferential data analysis techniques. The inferential tools adopted were T-test and ANOVA statistics to assess and examine the influence of some selected labour productivity factors on the outputs of the workers observed. The inferential test revealed the following; period of observation, shape of the building and mode of employment significantly affected outputs on the ten work items. The results of the analysis carried out established mean output values per day for: 150mm thick block in foundation (12.85m2); 150mm thick block in superstructure (13.22 m2); 150mm thick block in superstructure overhand (12.47m2); 225mm thick block in foundation (8.90m2); 225mm thick block in superstructure (11.17m2); 225mm thick block in superstructure overhand (9.16m2); 225mm thick block isolated piers in superstructure (5.00m2); 225mm thick block piers in superstructure overhand (4.57m2); 225mm thick block in pit bottom plan > 4 m2(7.85m2); 225mm thick block in bottom plan < 4 m2 (7.13m2). The study also identified forty-four (44) block work items not captured in BESMM3 and suggested that these work items be incorporated into BESMM3 for productive and cost implication. The research recommended that in compliance to BESMM3, the NIQS in collaboration with NJIC to sponsor a research on determination of labour outputs in all trades as a way to ensure uniformity in output constants. The study therefore finally concludes that SMM takes cognizance of productivity impact associated with labour and it is imperative for reliability and accuracy in block work estimate to empirically determine labour outputs on the basis of work items as stated in BESMM3.



1.1   Background of the Study

In Nigeria, like most developing countries, the construction industry plays a dominant role in the economic activities of the country.The efficiency of the construction industry has been established to heavily rely on its level of productivity. Construction productivity is constantly declining over a decade due to the lack of standard productivity data base system and ignorance of impact of various factors influencing labour productivity (Muqeemet al., 2011).The accuracy of the project cost estimates depend largely on the degree of accuracy of cost information obtained on the key components of an estimate (i.e. labour, plant, material, and profit and overhead) (Abdullahi, 2009), while the use of Standard Methods of Measurement (SMM) for the preparation of BOQ gives the quality and standard of the extent of work to be done, it also takes precedence of the cost significances of every classes of operations within a trade.

The common method of generating cost estimates for construction projects involves the multiplication of unit rate by the measured quantities in the bill of quantities (Ashworth, 2002).The unit rate is a component of labour rate (obtained from the multiplication of labour constant by all-in rate) plus cost of material and percentage allowance for profit and overhead, while the measured quantities are obtained from drawings and specifications for the works rules specified by Building and Engineering Standard Methods of Measurement (BESMM3). RISK IDENTIFICATION AND ASSESSMENT IN HOUSING DEVELOPMENT PROJECTS USING ANALYTICAL HIERARCHICAL PROCESS.