APPROXIMATE ESTIMATING
4. In order to make a preliminary estimate, before the plans of a structure are drawn, but after the general dimensions of the proposed building have been determined, architects and builders sometimes employ a method of approximate estimating, by which the cost is figured at so much per cubic foot of the building, the rate varying according to its character and the finish required. The method is also considerably used by insurance companies in fixing the amount to be placed on a building. It should be borne in mind that this method gives the approximate cost only, and should never be used in figuring the contract price of a building. This estimate, however, may be used to advantage in checking the accurate estimate, with which it will frequently be found to agree remarkably well.
TABLE I
COST OF BUILDINGS PER CUBIC FOOT
| Class of Building | Cost per Cubic Foot |
|---|---|
| Small frame buildings, costing from $800 to $1,500 | 10 to 12 |
| Frame houses, 8 to 12 rooms, costing from $1,500 to $10,000 | 12 to 15 |
| Reinforced-concrete mill buildings | 10 to 14 |
| Brick houses, 8 to 10 rooms | 15 to 18 |
| Highly finished city dwellings, brick or stone | 20 to 25 |
| Schoolhouses, brick | 12 to 20 |
| Churches, stone | 20 to 40 |
| Office buildings, well finished | 35 to 50 |
| Hospitals, libraries, and hotels | 35 to 50 |
[Table I] shows the approximate cost per cubic foot of various kinds of structures. In computing the contents of a building, there is no uniformity in practice, but no great error will be made in figuring the solid contents from floor of cellar to ridge of roof.
OUTLINE OF THE WORK
5. The drawings and specifications of a structure are the guides that the estimator must follow in making his computations. All measurements necessary for calculating the quantity of the materials required are obtained from the drawings; and all information in regard to the character of the workmanship and the quality of the materials to be used is furnished by the specifications.
In compiling a schedule, there are three stages to the operation: (1) Taking the dimensions for each of the various classes of work; (2) computing and collecting the quantities; and (3) estimating the cost.
In carrying out the first of these steps, each of its subdivisions should be considered in the order in which the work will be executed in the building. This order is about as follows: