Length of bearing in feet.

Breadth, 2 in.

Breadth, 2 1/2 in.

Breadth, 3 in.

Breadth, 3 1/2 in.

Breadth,

4 in.

Breadth,

4 1/2 in.

Breadth, 6 in.

Breadth, 5 1/2 in.

depth, inches.

depth, inches.

depth, inches.

depth, inches.

depth, inches.

depth, inches.

depth, inches.

depth, inches.

5

4 3/4

4 1/2

4 1/2

4

3 3/4

3 1/2

...

...

6

5 3/4

5 1/2

5

4 3/4

4 1/2

4 1/4

...

...

7

6 3/4

6 1/4

6

5 3/4

5 1/4

5

...

...

8

7 3/4

7 1/4

6 3/4

6 1/2

6

5 3/4

...

..

9

8 3/4

8

7 1/2

7 1/4

6 3/4

6 1/2

6 1/4

..

10

9 3/4

8 7/8

8 1/4

8

7 1/2

7 1/4

7

6 3/4

11

10 1/2

9 3/4

9 1/4

8 3/4

8 1/4

8

7 3/4

7 1/2

12

11 1/2

10 3/4

10

9 1/2

9 1/4

8 3/4

8 1/2

8 1/4

No. XIV. Table Of The Scantlings Of Purlins, Of Baltic Pine, For Roofs For Different Bearings, From 6 To 14 Feet; Distances Apart 6 Feet, 7 Feet, 8 Feet, 9 Feet. See Sect. IV., Art. 264

Length of bearing in feet.

6 feet apart.

7 feet apart.

8 feet Apart

9 feet apart

depth, inches.

bread;h, inches.

depth, inches.

breadth, inches.

depth, inches.

breadth, inches.

depth, inches.

breadth, inches.

6

6

3 1/2

6 1/4

3 3/4

6 1/2

4

6 3/4

4 1/4

7

6 3/4

4

7

4 1/4

7 1/4

4 1/2

7 1/2

4 1/2

8

7 1/2

4 1/2

7 3/4

4 3/4

8

4 3/4

8 1/4

5

9

8 1/4

5

8 1/2

5 1/4

8 3/4

5 1/4

9

5 1/2

10

8 3/4

5 1/4

9 1/4

5 1/2

9 1/2

5 3/4

9 3/4

11

9 1/2

5 3/4

9 3/4

5 3/4

10 1/4

6

10 1/2

6 1/4

12

10

6

10 1/2

6 1/4

10 3/4

6 1/2

11 1/4

6 1/4

13

10 3/4

6 1/2

11 1/4

6 3/4

11 1/2

7

12

7 1/4

14

11 1/4

6 3/4

11 3/4

7

12 1/4

7 1/4

12 1/2

7 1/2

Purlins of less scantlings than in the Table may often appear strong enough, but in such cases the common rafters will be found to bo stronger than is necessary. It is most economical to make the rafters no stronger than is necessary to carry the load between the purlins, and the purlins sufficiently strong to carry the rafters.

No. XV. Table Of The Scantlings, Of Common Rafters, For Roofs, For Different Bearings, From 5 To 20 Feet; Distance Apart 12 Inches. See Sect. IV.. Art. 265

Length of bearing in feet.

Breadth, 1 3/4 in.

Breadth, 2 in.

Breadth,

2 1/4 in.

Breadth, 2 1/2 in.

Breadth, 2 3/4 in.

Breadth, 3 in.

Breadth, 3 1/2 in.

Breadth, 4 in.

Breadth, 4 1/2 in.

depth, inches.

depth, inches.

depth, inches.

depth, inches.

depth, inches.

depth, inches.

depth, inches.

depth, inches.

depth, inches.

5

3

2 7/8

2 3/4

...

...

...

..

..

..

6

3 1/4

3 1/2

3 1/4

3 1/8

3

...

...

..

..

7

4 1/8

4

3 3/4

3 5/8

3 1/2

..

...

..

..

8

4 3/4

4 5/8

4 3/4

4 1/4

4 1/2

4

3 3/4

..

..

9

5 1/4

5 3/8

5

4 3/4

4 5/3

4 1/2

4 1/4

..

..

10

6

5 3/4

5 1/2

5 3/8

5 1/8

5

4 3/4

4 1/2

..

11

6 1/2

6 1/4

6

5 3/4

5 5/8

5 1/2

5 1/4

5

4 3/4

12

7

6 3/4

6 1/2

6 3/8

6 1/4

6

5 3/4

5 1/2

5 1/4

13

7 3/4

7 1/2

7 1/4

7

6 3/4

6 1/2

6 1/4

5 3/4

5 5/8

14

8 1/4

8

7 3/4

7 1/2

7 1/4

7

6 3/4

6 1/4

6 1/8

15

8 3/4

8 1/2

8 1/4

8

7 3/4

7 1/2

7 1/4

6 3/4

6 5/8

16

9 1/2

9 1/4

8 3/4

8 1/2

8 1/4

8

7 3/4

7 1/4

7

17

10

9 3/4

9 1/2

9

8 3/4

8 1/2

8 1/4

8

7 1/2

18

10 1/2

10 1/4

10

9 1/2

9 1/4

9

6 3/4

8 1/2

8

19

11

10 7/8

10 1/2

10

9 3/4

9 1/2

9

8 3/4

8 1/4

20

11 3/4

11 1/2

11

10 1/2

10 1/4

10

9 1/2

9

8 3/4

Roofs that are covered with plain tiles, or stone slate, will require rafters one-third stronger than is necessary for blue slate. The Table will answer for either, as it is calculated for blue slate; and if to the ' breadth found at the head of a column half of that breadth bo added, it will give the breadth required for stone slate, or plain tiles. Thus, for a rafter of 7 feet bearing, 4 inches by 2 inches is sufficient for blue slate; and therefore 4 inches by 3 inches is the scantling for stone slate, or plain tiles.

Purlins also require the same addition to their breadths when the covering is of plain tiles, or stone slates.