This section is from the book "Elementary Principles Carpentry", by Thomas Tredgold. Also available from Amazon: Elementary Principles Of Carpentry.
Length of bearing in feet. | Breadth, 1 1/4 in. | Brendth, 1 3/4 in. | Breadth, 2 in. | Breadth, 2 1/2 in. | Breadth, 2 1/4 in. | Breadth, 2 3/4 in. | Breadth. 3 in. | Breadth, 31/4 in. | Breadth, 3 3/4 in. | Breadth, 4 in. |
depth, inches. | depth, inches. | depth, inches. | depth, inches. | depth, inches. | depth, inches. | depth, inches. | depth, inches. | depth, inches. | depth, inches. | |
5 | 5 3/4 | 5 1/2 | 5 1/4 | 5 | 4 3/4 | 4 1/2 | 4 3/5 | 4 1/4 | 4 1/8 | 4 |
6 | 6 1/4 | 6 | 5 3/4 | 5 1/2 | 5 3/6 | 5 1/4 | 5 | 4 1/2 | 4 3/4 | 4 1/2 |
7 | 7 | 6 3/4 | 6 1/2 | 6 1/4 | 6 | 5 3/4 | 5 1/2 | 5 3/4 | 5 1/4 | 5 |
8 | 7 3/4 | 7 1/2 | 7 | 6 3/4 | 6 1/2 | 6 3/6 | 6 1/4 | 6 | 5 7/8 | 5 3/4 |
9 | 8 1/2 | 7 7/8 | 7 1/2 | 7 | 6 7/6 | 6 3/4 | 6 1/2 | 6 1/4 | 6 | 5 7/8 |
10 | 9 | 8 1/2 | 8 | 7 3/4 | 7 1/2 | 7 1/4 | 7 | 6 7/8 | 6 3/4 | 6 1/2 |
11 | 9 1/2 | 9 | 8 3/4 | 8 1/2 | 8 | 7 3/4 | 7 1/2 | 7 1/4 | 7 | 6 3/4 |
12 | 10 | 9 3/4 | 9 1/2 | 9 | 8 1/2 | 8 1/4 | 8 | 7 3/4 | 7 1/2 | 7 1/4 |
13 | 10 3/4 | 10 1/4 | 9 3/4 | 9 1/2 | 9 | 8 3/4 | 8 1/2 | 8 1/4 | 8 | 7 3/4 |
14 | 11 | 10 1/2 | 10 | 9 3/4 | 9 1/2 | 9 1/4 | 9 | 8 3/4 | 8 1/2 | 8 |
15 | 11 1/2 | 11 | 10 1/2 | 10 | 9 3/4 | 9 1/2 | 9 1/4 | 9 | 8 3/4 | 8 1/2 |
16 | 12 1/4 | 11 1/2 | 11 | 10 3/4 | 10 1/2 | 10 | 9 3/4 | 9 1/2 | 9 1/4 | 8 1/8 |
17 | 12 3/4 | 12 | 11 1/2 | 11 1/4 | 10 3/4 | 10 1/2 | 10 1/4 | 10 | 9 3/4 | 9 1/4 |
18 | 13 1/4 | 12 1/2 | 12 | 11 1/2 | 11 1/4 | 10 3/4 | 10 1/2 | 10 1/4 | 10 | 9 1/2 |
19 | 13 3/4 | 13 | 12 1/2 | 12 | 11 1/2 | 11 1/4 | 10 3/4 | 10 1/2 | 10 1/4 | 10 |
20 | 14 1/4 | 13 1/2 | 13 | 12 1/2 | 12 | 11 1/2 | 11 1/4 | 11 | 10 3/4 | 10 1/4 |
21 | 14 3/4 | 14 | 13 1/2 | 122 | 12 1/2 | 12 | 11 3/4 | 11 1/2 | 11 | 10 3/4 |
22 | 15 | 14 1/2 | 13 3/4 | 13 1/4 | 12 3/4 | 12 1/2 | 12 | 112 | 11 1/2 | 11 |
23 | 15 1/2 | 142 | 14 | 13 3/4 | 13 | 12 3/4 | 12 1/4 | 12 | 11 3/4 | 11 1/4 |
24 | 16 | 15 1/4 | 14 1/2 | 14 | 13 1/2 | 13 1/4 | 12 3/4 | 12 1/2 | 12 | 11 3/4 |
25 | 16 1/2 | 15 1/2 | 15 | 14 1/2 | 14 | 13 1/2 | 13 | 12 3/4 | 12 1/2 | 12 |
Example. - For a 14 feet bearing, a joist 10 by 2 is of the same degree of stiffness as one 9 by 3, or as one of any other depth opposite 14, with the breadth at the top of the column.
This Table was calculated by the equation (l2/b)1/2x2.2=d. See
Art.195.
 
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