CONSTRUCTION - MISCELLANEOUS COST DATA As the prices of labor and materials not only vary considerably in different localities, but are constantly shifting in the same locality, the reader will understand that it is impossible to give any quotations of prices that will be re liable as of permanent or universal application. Any quotations given must be taken merely as proportionate, to be used in comparison with known quantities and methods.
The successful estimator requires more than mere accuracy and quickness in figures. Ex perience and good judgment, familiarity with all the complicated details of the particular job in hand—these are factors of inestimable value, and they are qualities of an indefinable and in tangible nature. The contractor should sub scribe for the leading trade journals covering such portions of the construction field as he is interested in, and should keep an eye on current prices and discounts. He should also make it a practice in every case to file away his estimates, whether his bids based on them have been suc cessful or not. If successful, he can compare his estimated costs with those of actual construc tion; and if unsuccessful, he can broaden his grasp of things by noting in what items his esti mates have been too high or too low. In the preparation of future estimates, he will have at hand a great mass of data that will be of prac tical service. In every case he must acquaint himself with conditions, prices, and discounts current in the local market.
Under the limitations above outlined, the reader will find of much practical value the fol lowing paragraphs and quotations,* based on a general review of prices prevailing during the past four or five years: The cost of a structure is a function of the number of pounds of steel or cast iron, the num ber of cubic feet or yards of masonry, the num ber of bricks, the number of feet of board measure, the number of square feet of paving, of linear feet of handrailing, etc., that go to make up the whole. An estimate of the cost requires careful calculating of all of these, as well as a knowledge of a fair unit-price at which they can be put into the structure.
Cost estimates must be based on unit values. The accuracy of the estimate will often depend upon the particular unit at which the estimate starts. The cost per unit will depend upon the particular plant or equipment employed and its fitness to handle the work most economically.
The plant or equipment needed to do a piece of work should be selected with a view of the size of the work and the time in which it is to be finished. Large equipment cannot, in general, be used economically on a small job, and small equipment cannot be used economically on a large job. The size, for example, of a concrete plant, should be such that its normal daily ca pacity is about equal to the amount of concrete that it is desired to turn out per day. For maximum economy, a plant should be employed continuously. If stops must be made to wait for forms to be put in readiness, or for other causes, the concrete will cost more than if the work of the concrete mixing can be carried on continuously.
For small concrete jobs, such as pavement work, hand mixing is more economical. Small batches may be mixed with a hoe or shovels in a box. Half-yard batches should be mixed on a platform by at least two men with shovels. The platform may be made of a steel plate or of boards placed with close joints on a frame.
A typical gang, mixing and laying one-half cubic yard batches, is the following: 1 foreman, 2 men delivering sand and stone, 1 man deliver ing cement, 2 men mixing, 2 men delivering con crete, 1 man tamping. At $3.00 per day for the foreman, and $1.50 per day for each of the other men, the cost per day of the gang is $15.00. The gang should turn out about 20 to 25 cubic yards per day. This is a cost of 75 to 60 cents per cubic yard for labor.
A typical gang for mixing and laying by hand cubic yard batches, is as follows: 1 forethan, 3 men delivering sand and stone, 1 man delivering cement, 4 men mixing, 3 men delivering concrete, 2 men tamping. The cost of this gang at the same wages as above is $22.50 per day. They should turn out about 40 cubic yards per day, making the cost of labor 56 cents per cubic yard.