As an example of the labor connected with the above-mentioned cost of forms and center ing, we quote an answer to an inquiry made as to the cost of labor on building walls consisting of piers two feet square with eight-inch curtain walls between. The reinforcement consisted of an ordinary type of deformed bar: "The labor cost in concrete form building is a very uncertain figure, as no two men do the same amount of work per day. I have had a squad of carpenters and helpers who would build forms for 24 by 24-inch columns at less than 10 cents per foot height; and, again, I have seen it cost as much as 35 cents per foot. Then, condi tions make a wide difference; and I recall an instance where forms cost as much as 70 cents per cubic foot of concrete, as no form could be used over again in stories higher up. The side-wall forms are worth from 6 to 20 cents per square foot for labor ; but it is all guesswork, for even the nature of the lumber affects the labor cost data; besides, you must remember that the cost of forms is always the big item in reinforced concrete, and until we have a system of changeable forms it always will be. I recall an instance where a contracting firm under estimated the cost of forms $28,000 on a building which they contracted to build for the sum of $230,000. In fact, their estimate as to cost of forms was only $17,000, and the total cost amounted to $45,000.
"The cost of labor per cubic yard for reinforced work of sizes given will be as follows: First-story-columns, $2.35 per yard; walls, $2.75 per yard. Second-story columns, $2.66 per yard; walls, $3.00 per yard; and so on up. These figures are based on machine mixing and elevator." A consideration of the detailed costs of con crete construction will show quite clearly where the temptations lie for slighting the work on the part of inexperienced contractors. As an ex ample, take an eight-story office building which was recently erected in the East. In this build ing, which was 80 feet by 175 feet in ground plan, the percentage costs of the various items were as follows: Labor 38 per cent Cement 15 per cent Stone and lime per cent Steel 21 per cent Lumber 10 per cent Power per cent Miscellaneous, unclassified 5 per cent It is evident that the large items on this job were the labor, the cement, the steel, and the lumber. The lumber charge is for the material used in forms. Although the actual costs in the case of a factory building would be somewhat different, their relation, as shown by these per centages, would hold substantially true, except that there might be some saving in the amount of cement, steel, or lumber. In a word, that the
expense of these items could be varied more easily in this type of construction than in most others.
Table VII shows a detailed consideration of the costs of reinforced concrete construction work. The steel cost given at the end of the table applies only to cost of putting in place and does not cover purchase price. These costs were obtained from a very large corporation engaged exclusively in reinforced concrete work and em ploying as superintendents and foremen experi enced, skilled men. The average contractor handling occasional jobs cannot hope to reach these figures except under very favorable circumstances.
In the case of concrete piles—another of the many uses to which this valuable agent has been subjected—we again have the question as to how whose domain they are encroaching to a con stantly increasing extent.
One of the chief factors making towards the increased cost of wood piles, is their growing scarcity. This is largely due to the recklessness with which our forests are being yearly depleted. The cost of concrete piles, as compared with that of wood piles, was brought out in a striking man ner during the erection of the new buildings of the United States Naval Academy at Annapolis, Md. The original plans called for wood piles; but, as the allotment made for the various build ings had been exceeded, it was found necessary to reduce costs wherever possible. Calculations showed that by using concrete piles a saving of over $27,000, or more than 50 per cent of the cost of wood piles, could be effected. As a re sult, these piles were selected. The various fac tors which tended toward the economy resulting from the substitution of concrete piles, are thus stated by Walter R. Harper, inspector in charge of the work: 2,193 wood piles were replaced by 885 concrete piles; 4,542 yards of excavation were reduced to 1,038 yards, saving 2,504 yards; and 3,250 yards of concrete footing were reduced to 986 yards, thus saving 2,264 yards. Shoring and pumping, which would have cost $4,000 had wood piles been used, were entirely eliminated. This indicates, in a measure, the means by which foundation costs were reduced as stated. Fur thermore, the permanence of the foundation is beyond question. This would not have been the case had wood piles been used. Table VIII shows a detailed statement of the comparison.
The saving in the cost of foundations by the use of concrete piles was $27,458.18, or more than half the original cost of the foundations as designed with wood piles.