This section is from the book "A Treatise On Architecture And Building Construction Vol4: Plumbing And Gas-Fitting, Heating And Ventilation, Painting And Decorating, Estimating And Calculating Quantities", by The Colliery Engineer Co. Also available from Amazon: A Treatise On Architecture And Building Construction.
Scope Of Subject. The art of estimating is very important both to the architect and to the builder; to the latter, in that he must employ some systematic method of estimating in order to carry on his business successfully, and to the former for the reason that he should at all times be able to estimate the cost of the buildings which he designs.
The science-for such it is-of fixing prices on a piece of work in any branch of the building trades, must be based on an extended experience. Any one can, with a little practice, learn to take off the quantities of materials, but when it comes to determining the rates, only a person of large and varied knowledge of building and costs of various details can accurately estimate the time and labor required to complete the work. It is the aim of this section to put the student on the proper course to pursue in order to become a practical estimator. For this purpose, a number of detailed estimates, and a complete example in estimating, are given as guides; it should be remembered, however, that as the prices of materials and labor vary from those assumed, so will the estimates vary. The estimates given herein are, in general, net figures, and do not include any contractor's profit.
Qualifications Of The Estimator. In this country there are no standard or definite rules on estimating which hold good in every section, the builders of each locality having their own ideas and customs in regard to the subject; this fact, together with the difference in the cost of labor in various parts of the country and the fluctuations in the market price of materials, requires, as before remarked, that the really clever estimator be a man of long and varied experience in the business. There are, however, certain practical rules and suggestions that will materially assist in taking off the quantities, and in valuing the labor required for any building operation. These will be taken up and considered in detail in this section.
Important Factors. The prime considerations in making an estimate are time and accuracy; to these ends, the estimator must systematize his efforts and endeavor to do a maximum amount of work in a minimum amount of time; but not at the expense of accuracy, which is the most important factor, and which is only insured when the figures are carefully checked. The estimator should, therefore, while avoiding too great refinements in calculation, aim at correctness rather than speed in doing the work. Very frequently do the effects of haste and inaccuracy in estimating the cost of a structure become evident when it is too late to remedy the errors, resulting sometimes in the financial ruin of the builder who trusts too implicitly in the estimator's figures.
A record should be kept of all estimates made, as this kind of information is most valuable, and establishes a precedent upon which to base subsequent estimates, as well as a check on the work at hand.