LABOR ESTIMATE
TYPES OF LABOR ESTIMATES
Preliminary Manpower Estimate - are used to establish costs for budget
purposes and to project manpower requirements for succeeding projects
and deployments. The estimates are prepared from limited information:
general descriptions or preliminary plans and specifications that contain
little or no detailed information; for example, on the basis of area, length,
or other suitable measurement. In some cases, a comparison may be
made with similar facilities of the same basic design, size, and type of
construction. A good preliminary estimate should vary less than 15
percent from the detailed estimate.
Detailed Manpower Estimate - are used to determine the manpower
requirements for the construction of a given project and the local direct
labor requirements of a deployment. Detailed estimates are prepared
using the individual activity quantities taken from the activity work sheet.
Then, selecting from the appropriate table the man-hours per unit figure,
and multiplying by the quantity, the total man-hours required is obtained.
FACTORS AFFECTING PRODUCTION
These factors are: weather conditions during the construction period; the
skill and experience of the men who will perform the work; the time allotted for
completion of the job; the size of the crew to be used; the accessibility of the
site; and the types of material and equipment to be used.
Workload - The time allotted for construction of the project has a definite
bearing on the number of workers assigned to do the work. Rush jobs may
require a crew to work long hours and 7 days a week. A worker's
production per hour decreases sharply under these conditions. Sometimes
it is better to increase the number of workers in a crew or work several
crafts at the same time in one location in order to complete a job quickly.
When work area is crowded, workers are likely to get into each other's
way, or distract others in the area. The results are reduction in efficiency
so that more man-days are being used to accomplish the same amount of
work. The size of the crew can affect production in another way. Crews are
made up of workers with the various skills required to do a certain job and
are assigned to jobs as a crew. They vary in size. When a crew is assigned
to a job which will not take quite all day, there is tendency to slow down
and make the work last out the day.
Site Area - The space for equipment maneuverability, storage of materials,
and job layout, have significant impact on the productivity of the crew. Site
accessibility can affect labor requirements for a project. A hard-to-reach
site may cause irregular delivery of materials and time consuming delays,
which use man-hours without producing results. These factors must be
considered when estimating manpower requirements for a project.
Conditions may vary, cramped working area, no material storage, may
reduce productivity to .25 -.30 efficiency. An example of ideal working
conditions, large work area, no restrictions on use or equipment
maneuverability, all materials stored at the site with easy access, will rate
high .80's as productivity efficiency in that area.
Labor - The skill and experience of the workers who are assigned to the
work should be considered when deciding the man-hour range to use. The
production rate of experienced workers is better than that of a workers
with little or no experience. If a crew consists of a few experienced
workers and many inexperienced workers, the experience workers will use
part of their time instructing and training the inexperienced workers. If a
deployment consists of essentially the same type of construction on all its
projects, inexperienced workers will increase their skill before the
deployment is completed. Jobs performed towards the end of the
deployment, after many months of similar work are done quicker, and with
less effort. For example, a person with no training or experience will rate .
25 -.30, "A" school graduate may raise factor to .35 -.40, a 3rd class petty
officer will average .50 -.65, a journeyman with long experience at task ma
rate .80 -.85 in efficiency.
Supervision - The skill and experience of the crew leader has a definitive
bearing on how the crew performs. A 3rd class petty officer with little
training and experience may achieve .30 -.40 efficiency factor; a 2nd class
petty officer with repetitive projects, and leadership training will perform
an average range, for the Seabees, of .60 -.70; an experienced 1st class
petty officer may have .70 -.85 efficiency rating.
Job Condition - Conditions that a worker faces on the job effects
productivity. Low quality work requirements such as rough surfaces,
inexact cuts, where visibility is not important may have a .70 -.75
efficiency rating. Median quality requirements such as temporary
construction may have an average efficiency rating. High visibility projects
where highest quality and workmanship are required may have an
efficiency rating of .25 -.30. The types of material used may slow down job
progress significantly. Heavy wet clay is much more difficult to excavate
than sandy loam or sand. Bulky or heavy materials will require more time
and equipment than light, prepackaged, easy to handle materials. The
efficiency factor may range from .25 -.35 for heavy clays to .75 -.80 for
pelletized tiles. Time allocated for operations will give .30 -.40 for "short
fuse" or short duration projects to .65 -.80 for projects with adequate time.
Insect annoyance has to be taken under consideration. A site with great
number of mosquitos, gnats, or other insects will have a .30 -.40 efficiency
factor, where a site with no insects may rate .65 -.80.
Weather Condition - Weather conditions have an effect on the number of
manhours required to do a job. Cold, damp climates, as well as hot, humid
climates, reduce a worker's daily production and affect the output of
construction equipment. Although time lost due to rain is not normally
charged against a project, rain in the midst of a construction operation
slows production and sometimes causes additional work which increases
the number of man-hours required to repair damages, and to remove
water from work areas before construction can resume.
Equipment - The type of equipment available has considerable effect on
the amount of labor required to perform a certain task. It is, therefore,
necessary for the estimator to know what equipment will be used on a
project before he can make an accurate estimate of manpower
requirements. For instance, he needs to know whether soil is to be hauled
in trucks or scrapers and the equipment size (it will take twice as many
drivers and trucks if 5 cubic yard trucks are used instead of 10 cubic yard
trucks). The estimator needs to know if concrete is to be placed by cranes
and concrete buckets or with wheelbarrows, and if piles are to be driven
with a diesel hammer or a drop hammer. The conditions of the equipment
will dictate how often a piece has to go for repairs. Frequent breakdowns
and maintenance requirements will have efficiency as low as .30 -.40 for a
given task to high .60 -.75 for a new piece that stays on the job site and is
always operational and requires minimal maintenance.
Tactics and Logistic - Location of a job site will have tremendous impact on
the progress of the project; remote location, slow supply delivery, frequent
tactical delays will rate . 25 -.35 in efficiency factor. Project near the main
camp, prompt deliveries, no tactical delay will rate .70 -.80 in efficiency
factor.
PRODUCTION EFFICIENCY GUIDE
Man-Day Estimate: MD = (QTY / UNIT SIZE) x (MHRS / UNIT) / 8 x DF
MD = Man-Day Estimate
QTY = Material quantity from material take off (MTO)
UNIT SIZE = Obtained from labor estimating tables
MHRS/UNIT = Obtained from labor estimating tables
8 = 8 hours per one man-day
DF = Delay Factor obtained from production efficiency chart
Table Notes:
1. The weights of the elements can be adjusted if known facts so indicate.
2. Rainfall is normally treated separately in the area of calendar day
scheduling. Predictions of lost construction days are based on geographic
rainfall charts. Typhoon and hurricane seasons can cause considerable lost
time in securing job sites for alerts and warnings, even if work areas are
not directly in the path of the storm.
3. The tactical delay area of consideration should include: night travel
restrictions; mine sweeps on roads into the work area; preparation of zigzag trenches or individual protective measure; sabotage of equipment or
materials left on the job site; and any additional security requirements
which detract from the assigned work force.
4. The continual theft of tools and materials can affect production and is very
common in some areas of the world. This condition requires abnormal
controls and security, which in turn slows production.
5. The man-hour estimates contained in this manual are based on the
average Seabee Production Efficiency which is 67 percent.
