Construction Estimating Reference Data
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Introduction | Table of Contents | Back Cover

Introduction

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 data.

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.

Construction Descriptions
It's 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.

Conversion Tables
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.

Material Tables
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.

Labor Tables
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.

Experienced construction 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 this manual.

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 jobs.

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 equipment.

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 per hour.

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

Introduction | Table of Contents | Back Cover