570  On  the  Cost  of  Agricultural  Buildings. 
the  joint  is  adjusted,  and  this  hole  must  be  quite  square  with 
the  timbers  ; the  diameter  of  a trenail  should  be  one-tliird  of  the 
depth  of  the  tenon  from  the  shoulders.  Trenails  are  not  to  be 
depended  upon  for  the  strength  of  joints,  as  this  should  result 
from  combinations  of  one  timber  with  another,  and  it  is  only  for 
the  setting  up  that  their  assistance  should  be  required. 
The  following  are  the  best  known  scantlings  of  timber  with 
which  to  construct  roofs,  partitions,  and  framed  floors:  — 
Scantlings  for  Roofs,  Trusses  not  more  than  10  feet  apart,  Pitch  j 
of  the  span,  Yellow  Fir  Timber,  and  Slate  Covering. 
Span 
in 
feet. 
Tie  Beam 
in 
inches. 
King-Post 
in 
inches. 
Principals 
in 
inches. 
Struts 
in 
iuches. 
Purlins 
in 
inches. 
Com.  Rafters 
in 
inches. 
20 
9JX4 
4 x4 
4 x4 
3*x3 
8 x4£ 
3£x2 
22 
10  xi* 
4^X41 
41 X 4 
4 X3 
8 X 5 
3ix2i 
25 
101x5 
5 x 5 
5 X4 
'41x3 
8 X5 
4 x2* 
27 
11  X 6 
5^X5}, 
6 x4 
5 x 4 
Six  5 
4^x3 
30 
12  XG 
0 XG 
6 Xl* 
G x4 
8ix5 
5 x 3^ 
Scantlings  of  Girders,  10  feet  apart. 
Length 
in 
feet. 
Depth 
in 
inches. 
Breadth 
in 
inches. 
Length 
in 
feet. 
Depth 
in 
inches. 
Breadth 
in 
inches. 
8 
8 
51 
8 
9 
41 
10 
9 
7 
10 
10 
6* 
12 
10 
8 
12 
11 
67 
14 
11 
9* 
14 
12 
n 
16 
12 
10* 
16  - 
13 
18 
13 
11 
18 
14 
H 
20 
14 
11* 
20 
15 
10 
22 
141 
13* 
22 
16 
10f 
24 
15 
14f 
24 
17 
Hi 
26 
1G 
15* 
26 
18 
12 
Scantlings  of  Binding  Joists,  not  more  than  6 feet  apart. 
Length 
in 
feet. 
Depth 
in 
inches. 
Breadth  \ 
in 
inches. 
Length 
in 
feet. 
Depth 
in 
inches. 
Breadth 
in 
inches. 
6 
G 
4 
16 
11 
7f 
8 
7 
4* 
18 
12 
8* 
10 
8 
5* 
20 
13 
9 
12 
9 
6* 
22 
14 
91 
14 
10 
7 
24 
15 
10 
