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combination of the object of labor and means of work and human work (Muhlemann,
Oakland and Lockyer, 1997).
Time consumption in the production process of construction services, including construction
services supply (purchasing) process, should be understood as the time spent to complete
the task - services. This means that to make a change to one of these factors causes a
change in the time-consuming process (Wysocki and McGary, 2005). The process of supply
of construction services (pointing to the productive nature of the service) requires active
resource consumption (as defined above) and resources of passive means eg. material
resources (Grzyl, 2011; Ambroziak, 2007):
active resources (technical measures)
passive resources (material resources).
The time-consuming process, therefore, are the resources used during the time allotted for
the task (execution of the service). Given the fact that the purchasing process is preceded by
the vast majority of construction output, time-consuming of purchasing process and
construction services is determined at the stage of planning. A display by modeling the
proceedings on one task is sufficient to characterize the problem of defining timeconsuming.
To present the task the terms „z” is being used. To complete the task "z" there
should be active resources included in the set R = {r1, r2, ..., rn}, for which the amount of
work presented individually - in resource-hours - give the vector n = [n1, n2, ... nn]. To
complete the task "z", there should be an allocation of resources in a number of l (ri) for i =
1, 2, ..., n, allowing you to take a decision in determining the time, expressed in hours it
takes to complete a task in the supply in accordance to formula 1:
where p(z) - defines the scope of the task "z". If the task "z" will be the only task performed
by the resources set R, and resources will be on-site task "z" the whole duration, the
allocation of the associated loss (eg. in pln) due to incomplete use working time active
stocks, marked out by depending on the formula 2:
where c i is the unit loss (eg. in pln / hr.) due to incomplete use working time i resource.
Separate the losses c i we can determine by the rules bringing them into their calculations for
each resource under consideration by the formula 3:
where: c p i − the unit price of work of i resource, w kp ,w z − percentage rates of indirect costs
and profit.
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