Many studies conducted on construction productivity and tool time, have highlighted
the common fact that only a portion of the tool time of the site work crew has been
realistically effective in producing the desired output or the deliverables (Noor 1998,
Peer 1986, Jenking & Orth 2006, Ruwanpura et al. 2006). According to the
revelations of the majority of these time motion or tool time studies, general worker
time spent on a direct work related task, which is commonly called direct tool time,
lies between 40-60% of the total time spent on the task by an individual worker.
Around 40-60% of the total worker time has been spent on either the supporting tasks
or totally non-productive work tasks (Choy and Ruwanpura 2005, AACE
International Recommended Practice No. 25R-03, 2004, Thomas et al 2004 , Heather
& Summers, 1996).