TABLE 8.5 Allowable Spans in Feet and Inches for Low-Slope Raftera, Slope 3 in 12 or Less (No Celling) Allowable Extreme Fiber Stress in Bending F (psi). 1200 Raher Sie Sp 500 600 700 800 900 1000 1100 1300 1400 1500 1600 1700 1800 1900 10-10 11-7 0.55 9-5 0.48 7-8 14-2 124 12-4 124 O.80 9-2 10-0 17-5 13-0 0.94 13 0.82 9-2 13-7 14-9 15-4 1.56 13-3 135 10-10 15-11 16-5 16-11 2.09 17-10 033 7-11 0.29 6-6 0.24 12-1 1.09 11-9 0.94 9.7 225 15-1 1.97 0.67 10-0 140 12-10 1.73 13-9 1.50 113 1.22 20-11 191 14-2 1.65 11-7 247 15-6 12.0 0.44 10-8 14-8 0.58 8-2 0.70 1.07 10-0 O.88 121 10-5 0.99 19-6 140 16-10 121 13-9 0.99 181 11-11 2.14 2x6 16.0 0.38 7-1 12-4 8-8 0.57 16-3 080 12-8 031 13-3 0.44 11-6 0.38 048 15-3 067 13-3 0.58 10-10 067 17-1 0.94 14-10 077 L10 20-3 1.56 17-6 135 144 1.35 21-7 191 18-9 1.75 22-11 23-7 2.28 24.0 161 0.39 144 0.55 12-5 0.48 10-1 0.39 18-3 148 22-3 2.09 19-4 17-11 18-9 1.24 16-3 L07 13-3 088 033 10-6 16.0 0.29 8-7 024 15-5 033 13-4 0.29 10-11 0.24 18-9 033 16-3 0.29 13-3 0.24 1.09 2.47 19-10 20-5 12.0 1.73 18-2 15-6 0.94 12-8 0.77 22-10 23-11 14-0 2x8 0.70 11-6 0.82 12-1 0.67 1.65 14-10 1.50 181 15-9 L48 28-5 1.97 2.14 15-3 135 27-7 16-3 16-8 1.75 30-1 9.4 0.48 19-6 24.0 031 16-11 0.57 20-8 LI0 25-10 1.22 26-8 21-10 0.94 I8-11 0.82 161 29-3 2.28 25-4 24-10 1.56 224 1.35 18-3 12.0 0.44 14-8 038 11-11 031 20-6 044 17-9 038 14-6 0.31 067 16-11 0.58 13-9 0.48 23-9 0.67 0.55 15-10 048 0.80 17-11 0.70 14-8 0.57 25-2 0.80 21-9 0.70 17.9 0.57 1.09 124 19-10 20-8 140 21-6 121 1.73 23-2 1.50 18-11 191 23-11 1.65 196 1.35 33-6 191 29-1 1.65 2.09 24-7 247 26-0 1.97 20-8 2.14 21-3 2x10 160 094 16-2 0.7 107 16-11 -17-7 0.88 27-10 29-1 181 20-1 12-11 0.39 22-2 0.55 15-5 0.67 26-6 0.94 23-0 0.82 18-9 0.67 24.0 0.99 30-3 1.40 26-2 L10 314 1.56 27-2 135 122 32-6 1.48 34-7 2.09 161 35-7 2.28 1.75 36-7 2.47 12.0 19-3 0.48 15-8 0.39 20-6 0.58 16-9 0.48 1.09 24-1 094 124 25-2 1.73 28-2 1.50 23-0 1.22 29-11 30-10 31-8 1.97 2.14 25-2 25-10 2x12 16.0 19-8 0.77 1.07 20-6 0.88 121 21-5 0.99 22-2 1.10 23-9 24-5 148 24.0 1.35 1.61 1.75 "Criteria: 20 psf lve load, 10 paf drad load, live load deflection limited to Me of the span. Number shown in cach hox below the span is the minimum required modulus f elasticity in units ef 1.000.000 pai. Spans are meared along the horlenntal projection and loads ae onnnidend an applied slong the horizontal projection Sourer: Reprodaced from the Uiniform Bailding Cinde, 1991 edition, (Ret. 3), with permension of the publishers, International Conference of Building Officials Problem 8.8.C. Using Table 8.5, select the minimum size rafter for a span of 24 ft if rafters are 16 in. on center and the wood grade is Douglas fir-larch, No. 1 grade.
TABLE 8.5 Allowable Spans in Feet and Inches for Low-Slope Raftera, Slope 3 in 12 or Less (No Celling) Allowable Extreme Fiber Stress in Bending F (psi). 1200 Raher Sie Sp 500 600 700 800 900 1000 1100 1300 1400 1500 1600 1700 1800 1900 10-10 11-7 0.55 9-5 0.48 7-8 14-2 124 12-4 124 O.80 9-2 10-0 17-5 13-0 0.94 13 0.82 9-2 13-7 14-9 15-4 1.56 13-3 135 10-10 15-11 16-5 16-11 2.09 17-10 033 7-11 0.29 6-6 0.24 12-1 1.09 11-9 0.94 9.7 225 15-1 1.97 0.67 10-0 140 12-10 1.73 13-9 1.50 113 1.22 20-11 191 14-2 1.65 11-7 247 15-6 12.0 0.44 10-8 14-8 0.58 8-2 0.70 1.07 10-0 O.88 121 10-5 0.99 19-6 140 16-10 121 13-9 0.99 181 11-11 2.14 2x6 16.0 0.38 7-1 12-4 8-8 0.57 16-3 080 12-8 031 13-3 0.44 11-6 0.38 048 15-3 067 13-3 0.58 10-10 067 17-1 0.94 14-10 077 L10 20-3 1.56 17-6 135 144 1.35 21-7 191 18-9 1.75 22-11 23-7 2.28 24.0 161 0.39 144 0.55 12-5 0.48 10-1 0.39 18-3 148 22-3 2.09 19-4 17-11 18-9 1.24 16-3 L07 13-3 088 033 10-6 16.0 0.29 8-7 024 15-5 033 13-4 0.29 10-11 0.24 18-9 033 16-3 0.29 13-3 0.24 1.09 2.47 19-10 20-5 12.0 1.73 18-2 15-6 0.94 12-8 0.77 22-10 23-11 14-0 2x8 0.70 11-6 0.82 12-1 0.67 1.65 14-10 1.50 181 15-9 L48 28-5 1.97 2.14 15-3 135 27-7 16-3 16-8 1.75 30-1 9.4 0.48 19-6 24.0 031 16-11 0.57 20-8 LI0 25-10 1.22 26-8 21-10 0.94 I8-11 0.82 161 29-3 2.28 25-4 24-10 1.56 224 1.35 18-3 12.0 0.44 14-8 038 11-11 031 20-6 044 17-9 038 14-6 0.31 067 16-11 0.58 13-9 0.48 23-9 0.67 0.55 15-10 048 0.80 17-11 0.70 14-8 0.57 25-2 0.80 21-9 0.70 17.9 0.57 1.09 124 19-10 20-8 140 21-6 121 1.73 23-2 1.50 18-11 191 23-11 1.65 196 1.35 33-6 191 29-1 1.65 2.09 24-7 247 26-0 1.97 20-8 2.14 21-3 2x10 160 094 16-2 0.7 107 16-11 -17-7 0.88 27-10 29-1 181 20-1 12-11 0.39 22-2 0.55 15-5 0.67 26-6 0.94 23-0 0.82 18-9 0.67 24.0 0.99 30-3 1.40 26-2 L10 314 1.56 27-2 135 122 32-6 1.48 34-7 2.09 161 35-7 2.28 1.75 36-7 2.47 12.0 19-3 0.48 15-8 0.39 20-6 0.58 16-9 0.48 1.09 24-1 094 124 25-2 1.73 28-2 1.50 23-0 1.22 29-11 30-10 31-8 1.97 2.14 25-2 25-10 2x12 16.0 19-8 0.77 1.07 20-6 0.88 121 21-5 0.99 22-2 1.10 23-9 24-5 148 24.0 1.35 1.61 1.75 "Criteria: 20 psf lve load, 10 paf drad load, live load deflection limited to Me of the span. Number shown in cach hox below the span is the minimum required modulus f elasticity in units ef 1.000.000 pai. Spans are meared along the horlenntal projection and loads ae onnnidend an applied slong the horizontal projection Sourer: Reprodaced from the Uiniform Bailding Cinde, 1991 edition, (Ret. 3), with permension of the publishers, International Conference of Building Officials Problem 8.8.C. Using Table 8.5, select the minimum size rafter for a span of 24 ft if rafters are 16 in. on center and the wood grade is Douglas fir-larch, No. 1 grade.
Chapter2: Loads On Structures
Section: Chapter Questions
Problem 1P
Related questions
Question
Transcribed Image Text:TABLE 8.5 Allowable Spans in Feet and inches for Low-Slope Raftern, Slope 3 in 12 or Less (No Celling
Siat Spacing
IN)
Allowable Extreme Fiber Stress in Bending F (pai).
1200
500
600
700
800
900
1000
1100
1300
1400
1500
1600
1700
1800
1900
11-7
13-0
0.94
13-7
109
11-9
0.94
9.7
14-2
124
12-4
14-9
154
15-11
16-5
191
14-2
16-11 17-5
2.28
15-1
9-2
10-0
17-10
10-10
0.55
9-5
12-4
0.67
O80
10-8
1.56
13-3
12.0
2.09
033
7-11
0.29
6-6
0.44
140
12-10
1.73
13-9
247
156
10-0
058
8-2
113
0.82
9-2
8-8
14-8
1.35
10-10
0.70
107
10-0
121
10-5
0.99
19-6
1.50
1.65
11-7
181
11-11
1.97
12-4
214
12-8
2x6
160
0.38
7-1
0,48
7-8
0.39
8-8
11-3
1.22
20-11
L73
18-2
0.24
12-1
0.33
10-6
0.29
8-7
024
15-5
0.33
13-4
0.31
13-3
0.44
11-6
0.48
15-3
0.57
16-3
0.67
17-1
0.77
17-11
0.88
18-9
L10
20-3
1.35
21-7
148
22-3
2.09
1.75
22-11 23-7
2.28
24.0
1.61
144
067
13-3
0.94
14-10
1.09
15-6
124
16-3
140
16-10
121
13-9
0.99
24-10
1.56
17-6
12.0
0.55
12-5
0.48
10-1
0.39
0.80
14-0
191
18-9
2.47
19-10 20-5
19-4
0.70
I1-6
2x8
16.0
0.38
94
0.58
10-10
0.82
12-1
0.67
0.94
12-8
1.07
13-3
1.35
144
1.10
1.50
14-10
1.65
15-3
181
15-9
1.97
16-3
161
29-3
2.28
2.14
16-8
031
16-11
0.57
20-8
0.80
0.77
088
1.75
30-1
247
24.0
0.48
19-6
0.67
16-11
21-10
0.94
I8-11
1.22
26-8
1.73
23-2
135
27-7
1.91
23-11
1.48
28-5
2.09
24-7
22-10 23-11
25-10
18-3
0.55
15-10
048
12-11
1.56
224
12.0
0.44
14-8
1.09
1.24
19-10 20-8
140
17-11
0.70
14-8
0.57
21-6
25-4
26-0
1.35
18-3
16.0
029
10-11
024
18-9
033
16-3
0.38
11-11
058
13-9
0.82
155
094
121
16-11 -17-7
0.88
1.07
1.50
18-11
1.65
19-6
1.35
33-6
1.91
29-1
1.65
23-9
1.81
20-1
197
20-8
2.14
21-3
1.75
2x10
16-2
031
20-6
0.39
22-2
0.48
23-9
0.67
20-6
0.58
16-9
0.67
26-6
0.94
0.77
L.10
31-4
1.56
27-2
122
32-6
24.0
0.99
30-3
1.40
26-2
1.48
34-7
2.09
161
35-7
25-2
0.80
27-10 29-1
36-7
12.0
0.44
17-9
0.55
19-3
1.09
24-1
094
19-8
0.7
124
25-2
1.07
20-6
0.88
1.73
28-2
2.28
2.47
30-10 31-8
197
25-2
21-9
23-0
29-11
0.29
13-3
24.0 024
0.38
14-6
031
0.70
17.9
0.57
0.82
18-9
0.67
121
21-5
135
22-2
1.50
23-0
1.22
181
24-5
2.14
25-10
2x12 16.0
0.48
15-8
0.39
0.48
0.99
1.10
1.35
1.48
1.61
1.75
"Criteria: 20 psf live load, 10 puf dead load, live load deflection limited to e of the span. Number shown in cach box below the span is the minimam required modulus
f elasticity in units of 1,000,000 pei. Spams are measured along the horienetal projection and loads are eonsidered an applied along the horizontal projection.
Sourer: Reprodaced frem the Uiniform Bailding Cinde, 1991 edition, (Ret. 3), with perminnion of the publishers, International Conference of Bluikding Officials
Problem 8.8.C.
Using Table 8.5, select the minimum size rafter for a span of 24 ft if
rafters are 16 in. on center and the wood grade is Douglas fir-larch, No.
1 grade.
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