42. Carpentry should include general framing, roofs, floor joists, partitions, sheathing, flooring, furring, and plastering grounds.
43. Board Measure.—The rough lumber used in framing is measured by the board foot, which means a piece 12 inches square and 1 inch thick. Lumber is always sold on a basis of a thousand feet board measure. The customary abbreviation for the latter term is B. M.; that for thousand is M. Thus, 500 feet board measure, costing $27 per thousand, would be written: 500 ft. B. M., at $27 per M.
To obtain the number of board feet in any piece of timber, the length, in inches, should be multiplied by the end area, in square inches, and the result divided by 144. For example, the number of feet B. M. in a floor joist 20 feet long, 3 inches thick, and 10 inches deep is 240 inches (=20 feet × 12) multiplied by 30 square inches (the end area) divided by 144, or 50.
The following rule is used by most contractors and lumber dealers: Multiply the length in feet by the thickness and width in inches, and divide the product by 12. Thus, a scantling 26 feet long, 2 inches thick, and 6 inches wide contains
| 26 × 2 × 6 | = 26 feet B. M. |
| 12 |
This rule, expressed in a slightly different manner, is more convenient for mental computation: Divide the product of the width and thickness in inches by 12, and multiply the quotient by the length in feet. Thus, a 2" × 10" plank, 18 feet long, contains
| 2 × 10 | × 18 = 30 feet B. M. |
| 12 |
44. Prices of Lumber.—Owing to the continual variation in the prices and grades of lumber, it is impossible to give prices here that will not vary from day to day. The architect before starting to estimate should first be sure that he has the latest lumber prices obtainable. These prices can always be secured from the local lumber dealer.
45. Studs.—To calculate the number of studs—set on 16-inch centers—the following rule may be used: From the length of the partition, in feet, deduct one-fourth, and to this result add 1. Count the number of returns, or corners, on the plan, where double studding is required, and add 2 studs for each such return. (The reason for adding 1 is to include the stud at the end, which would otherwise be omitted.) The sills, plates, and double studs must be measured separately.
