COST OF REINFORCED CONCRETE As a general proposition, reinforced concrete is almost invariably the lowest priced fireproof material suitable for factory construction. The cost is nearly always lower than that for brick and tile; and, with lumber at a high price, it is frequently even lower than brick and timber, with the added advantage of durability and fire protection.
In comparing the cost of different building materials, one must bear in mind that the con crete portion of the building is only a part of the total cost. Since the cost of the finish and trim may equal or exceed that of the bare structure, even if the concrete itself cost, say, 10 per cent more than brick and timber, the cost of the building complete may not be 5 per cent greater than with timber interior. The lower insurance rates will partly offset this even if there is no other economical advantage for the fireproof structure.
The exact cost of a building in any case is governed by local conditions. In reinforced con crete, the design, the loading for which it must be adapted, the price of cement, the cost of ob taining suitable sand and broken stone or gravel, the price of lumber for forms, the wages of the laborers and carpenters, are all factors entering into the estimate. Reinforced concrete is largely laid by common labor, so that high rates for skilled laborers affect it less than many other building materials.
As a general proposition, it may be stated that the cost of reinforced concrete factories fin ished complete with heating, lighting, plumbing, and elevators, but without machinery, may run, under actual conditions, from 8 cents per cubic foot of total volume measured from footings to roof, to 16 cents per cubic foot. The former price may apply where the building is erected simply for factory purposes with uniform floor loading, symmetrical design—permitting the forms to be used over and over again—and with materials at moderate prices. The higher price will usually cover manufacturing buildings, lo cated in restricted districts, and where the ap pearance both of the exterior and interior must be pleasing. This does not include in either case interior plastering or partitions.
Professor C. Derleth, Jr., says: "No doubt you have been told that there are many systems for reinforced concrete construction, and some of you may be in doubt as to what type should be used. In
general, a building of reinforced concrete, designed irre spective of a distinct type or system, will cost more money than an alternate design recognizing a well developed method. This difference in cost results, not because a patented system has superior merits theoret ically, but because it has been tried—because the mate rials are manufactured according to system and may be readily obtained; moreover, because a company repre senting a responsible system may be counted upon to fur nish high-grade materials." Along this same line of thought in regard to the intelligent placing of the steel work in rein forced concrete structures, it seems in place to introduce a statement made by Buel and Hill: "The compressive resistance of concrete is about ten times its tensile resistance, while steel has about the same strength in tension as in compression. Volume for vol ume, steel costs about fifty times as much as concrete. For the same sectional areas, steel will support in com pression thirty times more load than concrete, and in tension three hundred times the load that concrete will carry. Therefore, for duty under compression only, con crete will carry a given load at six-tenths of the cost required to support it with steel. On the other hand, to support a given load by concrete in tension would cost about six times as much as to support it with steel. If the various members of a structure are so designed that all of the compressive stresses are resisted by concrete, and steel is introduced to resist the tensile stresses, each mate rial will be serving the purpose for which it is the cheap est and best adapted, and one of the principles of eco nomic design will be fulfilled." In the cost of plain work such as the con struction of reinforced walls and foundations, labor has much to do with the cost. The cost of reinforcement for such walls can be easily com puted from the current price of steel bars. This cost is sometimes lowered by using material taken from other sources; but in using such ma terial, care should be taken that it is in good condition both as to quality and strength.