Five-story tenements, built on 25x100, cost, as is well known, within the limit of $15,000 to $20,000, or at the rate of eleven to fifteen cents per cubic foot.

Six-story modern non-fireproof tenements, without elevators, commonly known as "walk ups," cost from twelve to sixteen cents per cubic foot to construct and are usually built on lots larger than 25x100, of which they cannot cover more than 70% of a lot, where the old style twenty-five foot house could use 75% of the lot. They are usually of very cheap construction and built to accommodate the families of day laborers whose earnings are near the bottom of the scale.

Six-story elevator apartment dwellings, non-fireproof, cost from fifteen to eighteen cents per cubic foot to build, and accommodate quite a large class of people who are able to pay from $7 to $10 per room per month.

Seven-story elevator apartment dwellings which are called semi-fireproof, vary in cost between somewhat wider limits, fireproof apartment dwellings of greater height costing from twenty-five to fifty cents per cubic foot to erect.

Non-fireproof store and loft buildings cost twelve to eighteen cents per cubic foot and the same, called fireproof, to any height, built of steel, cost from eighteen to thirty-five cents per cubic foot.

Office buildings cost from twenty-five to fifty cents per cubic foot.

Stable property, garages and factories cost from fifteen to twenty-five cents per cubic foot, according to character of construction.

New buildings are estimated at what they probably cost, and the value of the land is added to that to obtain the value of all.

The process of computing the cost of construction is to obtain the area of land covered, the height of the building, calculate its cubical contents in feet, and multiply by the figure determined upon as probably representative of the cost of building per cubic foot.

Example

To illustrate, take a corner property six stories high, covering 90% of a rectangular plot of four city lots, or 100x100, at the corner of an intersecting street and avenue. This shows an area covered of 9,000 square feet with twelve feet between floors or 84 feet in height above cellar bottom.

9,000 x 84 = 756,000 cubic feet.

Say that the character of construction warrants a cost unit of 18 cents per cubic foot, we have then 756,000 cubic feet by 18 cents or $136,080.

Supposing the land to be worth $20,000 per city lot as a land unit of value. Then 100x100, as a corner, following the method of land valuation outlined at the beginning of the lecture, would develop a full value as follows:

The unit of cost of construction is worked out from the average experience of the appraisers. The cost of a number of typical buildings is ascertained to lie within certain limits, and constant association of those units so derived with certain forms and appearances of construction has enabled us to make close approximations of actual cost (or what that cost should reasonably have been), to suit the purpose for which the building was erected.