=50. Cost per Square Foot.=—For all classes of materials that enter into the general framing and covering of a building, a close estimate may be made by analyzing the cost per square foot of surface; that is, the cost of labor and materials—studs and sheathing in walls, joists and flooring in floors, etc.—required for a definite area should be closely determined, and this cost divided by the area considered, will give the price per square foot. If the corresponding whole area is multiplied by the figure thus obtained, the result will, of course, be the cost of that portion of the work. While the usual custom is to adopt a uniform rate for the various grades of work, a careful analysis will show that roof sheathing, where the roof is much cut up, costs more in place than wall sheathing, owing to its position; also that the studs in walls and partitions cost more than floor joists, as they are lighter and require more handling. The following example shows how to determine the cost per square foot of flooring and indicates the general method to be pursued in similar cases. The area used in the calculation is a square, or 100 square feet. The cost of labor is estimated at 40 per cent. of that of the materials, as it has been shown by experience that this allowance is a very close approximation to the actual cost of general carpenter work. COST OF FINISHED FLOOR PER SQUARE Joists, hemlock, 8 pieces, 3" × 10" × 10', 200 feet B. M., at $27 per M. $ 5.40 Bridging, hemlock, 7 sets, 2" × 3" × 1' 4", 9 feet B. M., at $27 per M. .24 Rough flooring, hemlock, ⅛ inch thick, laid diagonally, 100 ft. + 25 ft. + 10 ft., 135 feet B. M., at $25 per M. 3.38 Finished flooring, No. 2, white pine, ⅞ inch thick, 125 feet B. M., at $45 per M. 5.63 Nails, eightpenny (about) 3 pounds, at $2.50 per 100 pounds .08 Labor, 40 per cent. of cost of materials 5.89 ------ Total cost for 100 square feet $20.62 Cost per square foot, $20.62 ÷ 100 = 21 cents. A similar method may be followed in estimating the cost of interior finish, paneling, doors, etc.