Figure 2-2.--Estimating time required for a gangway repair job.
F. Drying time (8 hours). This must be counted in
the total estimate even though no work can be
done on the gangway during this period.
G. Giving the second coat of varnish. This step
might take one person about 1 hour.
H. Drying time (8 hours).
I. Putting on the metal fittings. This step might
take one person about 1 hour.
Notice that, although there are four people available
to work on this job, it is not possible for all four to be
working on it at all times. Most of the work must be
done in sequence; for example, you can't finish the
So you find that the total job requires 33 man-hours
surface before you have renewed the stringer and treads,
of work. But what does this mean? Does the number of
and you can`t make the new stringer and treads before
you have made the template. Step A (obtaining the
man-hours tell you how long the job is going to take?
metal fittings) could be performed at any convenient
Is it safe to assume that a job requiring 33 man-hours
time before step I (putting on the metal fittings). The
can be done in 8 1/4 hours if you put four people to
advantage of using a diagram such as the one shown in
work on it? Obviously not, since there is a limit to the
figure 2-2 is that it shows at a glance the total number
number of people who can work on the job at any
of hours that must be allowed for the work-in this
case, 28 hours.
The unit MAN-HOURS, then, is a measure of
The diagram shows you something else, too: the
amount of work but not of total length of time. You
number of man-hours required for each step. Let's add
should be very cautious about using man-hours when
estimating how long a job will take, since this measure
does not allow for the sequence in which the work must
be performed, the number of steps required, or the
number of people who can work on the job at each