Table of Contents |
Most construction estimators
accumulate tables, man-hour records, and useful data during their entire
career. Few ever organize and compile this valuable information into a
form that could be used by other estimators. This manual is an attempt to
assemble in a convenient form a career's worth of estimating reference
The content of the book is limited
to estimating reference materials; no dollar costs and very little
engineering data are included. If you need engineering, architectural or
dollar cost data, many other publications are available. Nowhere in this
book do we explain how to compile an estimate. Again, many other books
explain estimating procedures.
We generally follow the Uniform
Construction Index format to organize the book into sections. If you've
used the 16 division UCI system before, you'll have no trouble turning
right to the section that has the information you need. For those not
familiar with the UCI system, an exhaustive index is provided at the back
of this book.
The information you find here
falls into four categories: Construction Descriptions, Conversion Tables,
Material Tables, and Labor Tables.
difficult or impossible to estimate the cost of any work you can't
visualize. Consequently, many pages of text and illustrations are
included in this book to familiarize you with the work involved. But a
much larger volume would be needed to describe all construction work. In
fact, a whole library of books would be required. The descriptions
included here only highlight information that will be of particular
interest when estimating the type of work covered.
Every estimator needs to make conversions:
from tons to cubic yards; from linear feet to board feet; from bank to
loose measure. There's no substitute for the exact conversion table you
need, and this manual will most likely have what you're looking for.
Properties of materials are an important
subject for every construction estimator: What types of materials are
generally available, in what finishes, in what weights, in what sizes? A
good, non-technical summary of key materials and how they are used will be
found in many sections.
Most of this book is devoted to man-hour
estimating tables, and for good reason. The labor required is a key
element in every construction estimate. Because there are so many labor
tables in this book, and because labor is such an important part of every
estimate, an in-depth explanation of the labor tables is appropriate.
estimators recognize that no two jobs are exactly alike. Labor
productivity varies widely from job to job, even if the crew remains the
same. Thus, judgment is an essential element in every construction
estimate. And judgment will be required when using the labor tables in
The man-hour tables in this book
are not based on "ideal" conditions. They assume conditions typical
of what most contractors encounter on better planned and managed jobs. The
labor productivity indicated in the tables will apply to the extent that
these conditions apply to the job you are figuring. Where conditions
differ, modification will be necessary.
Specifically, the man-hour tables
are based on the following assumptions:
Size of the job is
moderate, about what most contractors handling this type of work are
accustomed to bidding.
The materials needed are
readily available at a storage point relatively close to the point of
installation. The materials are service grade and meet generally accepted
standards for the type of use intended.
Layout and installation are
relatively uncomplicated because the plans and specifications are
adequate, access to the work is good, and work done by other trades
was done according to the plans and is professional quality.
Labor productivity is fair
to good. The crew is experienced in this type of work, motivated to
complete the work as required, and is just large enough to get the job
done using routine procedures.
Temperature and working
conditions do not adversely affect progress of the job.
Tools and equipment
appropriate for the job are available and used to best advantage during
the course of construction.
Work is professional quality.
However, exceptional work involving great detail, decorative
materials, custom treatments or unique skills is not considered. Any
defects or omissions are remedied before the crew leaves the job site.
Only new construction is
involved. Repair, replacement and remodeling- type work often involves
problems of limited access, matching of materials, working with
non-standard sizes, patching, and control of the construction environment.
The tables will be a useful guide to the extent that repair or remodeling
work is similar to new construction.
Scope of the Work Described
The man-hour tables in this book will be a
useful guide if you can visualize what work is included and what work is
excluded from the tasks listed in each table. No man-hour estimate is
useful if there is considerable doubt about what the figures actually
cover. Most labor tables in this book have a footnote which should clarify
the scope of work included. But it would be nearly impossible to describe
in detail every element of each man-hour estimate.
It is safe to assume, however,
that every task essential to performing the work has been included in the
estimate. If the scope of work covered still is not clear, understand that
estimates are for the "complete" job and include all of the associated
work usually performed along with the named task unless noted otherwise.
But be aware that most tables
include work by only one trade classification. This should help you define
what is included and excluded from each table. For example, man-hours for
installing a cabinet (by a carpenter) would not include the time to stain
and seal the cabinet (by a painter).
Two categories of work are
specifically included and excluded from the man-hour tables:
Non-productive labor is not
included unless noted otherwise. On larger crews it is assumed that the
supervisor works along with the crew when not actually directing the work.
Mobilization and demobilization
on the site are included. Time usually spent unloading tools,
materials and equipment, and preparing to do the work is included in the
man-hour estimates. So is time spent reloading tools and equipment at job
completion and cleanup of surplus material. Naturally, no travel time or
delays off the site are included unless specifically noted.
How Accurate are the Tables?
The figures published here are the result of
actual observations compiled, interpreted, and verified by professional
estimators. This implies an exercise of judgment. And it should be clear
to the user that this manual is the product of personal judgment. Grew
productivity varies widely. Even the most well-informed, professional
judgment can not guarantee that the figures here will apply to the job
you are estimating.
In the aggregate the man-hour
estimates in this manual will be accurate to within about 20% on most jobs
where conditions are similar to the conditions outlined. On most of the
remaining jobs the figures will be too high by 20% or more - estimating
more man-hours than are actually required. This is intentional, as an
estimate slightly too high is better than an estimate slightly too low.
Most contractors would agree.
Let's look at an example. This
book lists labor installing asphalt strip shingles at 1.5 man-hours per
100 square feet. A skilled shingle specialist working under ideal
conditions on a larger job will be able to handle considerably more work
than this. You'll hear claims of 200 or more square feet per man-hour. At
that rate a two man crew would finish two 1600 square foot roofing jobs in
a day. That's an excellent rate. But it's not a rate most estimators
should use until they saw their crews produce results like that on several
Now look at the other extreme.
Estimators who have figured asphalt shingles on commercial, better
industrial or military jobs claim that 2 to 2.5 man-hours per 100 square
feet is a reasonable figure. We don't doubt the validity of these
estimates for that type of work.
Most jobs fall between these
extremes. Many experienced roofing contractors would insist that their
crews can average close to 100 square feet per man-hour. Thus a two man
crew would finish that 1600 square foot job in one 8 hour day. That's 33%
faster than the 1.5 man-hours listed on page 192 of this manual.
Again, we don't doubt the validity
of these figures. But we recognize that they are based on specialized
crews working under experienced super- visors and with exactly the right
To summarize, reasonable estimates
for installing asphalt strip shingles may vary from .5 to 2.5 man-hours
per square, with most experienced crews producing about 100 square feet
Why the difference? There are many
reasons. The highest and lowest productivity rates vary from the
conditions outlined above and probably don't include and exclude the same
tasks. Many shinglers can put down 200 square feet of shingles in an hour.
But every shingle job involves checking and cleaning the deck, moving
tools and materials into place, laying out the job, placing felt and
starter strips, some flashing work, making minor repairs and cleanup. All
of this should be included in any realistic estimate and is included in
the 1.5 hour estimate in this book.
Another difference is the type of
work itself - even though the material applied fits the same description.
Commercial jobs nearly always receive higher quality workmanship than the
typical residential job. Every tradesman worthy of your payroll will give
more care and attention to a highly visible root on a commercial building
covered with top quality shingles than a garage root using strictly
standard grade shingles.
Recognize also that an experienced
crew working under the direct supervision of an owner-entrepreneur will
out-produce less motivated tradesmen on nearly every job. And a crew
working on a piecework basis will do its level best to get the job done by
quitting time so a return trip isn't necessary the next day.
No single figure will cover all
work and a 500 word essay would be needed to describe most common
situations. In this book we have selected what we feel are reasonable
first approximations for labor productivity. Use these figures when the
productivity of the crew is unknown and the exact type of work is not
specified. In the case of asphalt strip shingles, 1.5 man-hours was our
choice. And that brings us to our final, and most important point.
Every man-hour estimate in this
volume is a poor second choice when compared to the figures you develop
yourself from the work your crews have handled. Your most reliable guide
will always be your own cost records. Where you must supplement your
experience with the reference data in this manual, we hope our judgment
proves worthy of your trust
Table of Contents |
Paperback, 384 pages
Construction Estimating Reference Data