Roof Truss Span Tables
Alpine truss designs are
engineered to meet specific
span, configuration and load
conditions. The shapes and
spans shown here represent
only a fraction of the
millions of designs processed
by Alpine engineers.
Total load(PSF)
Duration factor
Live load(PSF)
Roof type
55
1.15
40 snow
shingle
47
1.15
30 snow
shingle
40
1.15
20 snow
shingle
55
1.15
2x4
2x4
2x6 2x6
2x4 2x6
2/12
2.5/12
3/12
3.5/12
4/12
5/12
6/12
7/12
24
29
34
39
41
44
46
47
24
29
34
39
43
52
60*
67*
33
39
46
53
59
67*
69*
70*
27
33
37
41
43
46
47
48*
27
33
39
44
49
58
67*
72*
37
45
53
61
64
69*
71*
72*
31
37
40
44
46
49
51
52*
31
38
44
50
56
66
74*
77*
43
52
60
65
69
74*
76*
77*
33
39
43
47
49
53
55
56*
33
40
46
52
57
66
74*
80*
46
55
64
70
74
80*
82*
83*
2/12
2.5/12
3/12
3.5/12
4/12
5/12
24
28
30
33
35
38*
24
29
33
37
41
47*
33
40
45
49*
52*
57*
25
29
31
34
36
39*
27
32
37
41
45*
51*
38
43
47
51*
54*
59*
27
31
34
36
39
42*
31
37
42
46
50*
56*
41
46
50
54*
58*
63*
29
33
36
39
42*
45*
32
37
42
46
49*
54*
44
49
54
58*
62*
68*
6/12 - 2/12 ‡
6/12 - 2.5/12 ‡
6/12 - 3/12 ‡
6/12 - 3.5/12 ‡
6/12 - 4/12 ‡
40
37
33
28
22
43
38
33
28
22
59*
52
45
38
31
42
38
35
32
26
49
44
38
32
26
62*
57*
52
44
36
45
41
38
34
30
56*
50
43
37
30
66
61*
56*
50
41
48
44
40
36
32
57*
52
46
39
32
71*
66*
60*
54
44
Pitch
Common -- Truss configurations for the
most widely designed roof shapes.
Mono -- Used where the roof is required to
slope only in one direction. Also in pairs
with their high ends abutting on
extremely long spans with a
support underneath
the high end.
Scissors -- Provides a cathedral or
vaulted ceiling. Most economical when the
difference in slope between the top and
bottom chords is at least 3/12 or the bottom
chord pitch is no more than half the top chord
pitch.
20 **
shingle
**construction
or rain,
not snow load
30 snow
tile
Top Chord
Bottom Chord
40
1.25
2x4 2x6 2x6
2x4 2x4 2x6
2x4 2x6 2x6
2x4 2x4 2x6
2x4 2x6 2x6
2x4 2x4 2x6
Spans in feet to out of bearing
‡ Other pitch combinations available with these spans
For Example, a 5/12 - 2/12 combination has approx. the same allowable span as a 6/12 - 3/12
Flat -- The most economical flat truss for a
roof is provided when the depth of the truss in
inches is approximately equal to 7% of the
span in inches.
Total load(PSF)
Duration factor
Live load(PSF)
Top Chord
Bottom Chord
55
1.15
40 snow
2x4
2x4
2x6 2x6
2x4 2x6
23
25
27
29
32
33
34
36
39
40
44
45
24
27
28
30
32
33
34
36
39
42
47
51
Depth
16"
18"
20"
24"
28"
30"
32"
36"
42"
48"
60"
72"
47
1.15
30 snow
2x4 2x6 2x6
2x4 2x4 2x6
40
1.15
20 snow
2x4 2x6 2x6
2x4 2x4 2x6
40
1.25
20 rain or constn.
2x4 2x6 2x6
2x4 2x4 2x6
Spans in feet to out of bearing
25 §
28
30
33
36
38
39
42
45
49
55
60
25 §
27
28
31
34
35
36
39
41
43
46
48
25 §
27
28
31
33
35
36
38
41
44
49
54
25 §
29 §
32
35
39
40
42
45
48
52
58
64
25 §
29 §
31
34
37
38
39
42
44
46
48
51
25 §
29 §
30
33
36
37
39
41
44
47
53
57
25 §
29 §
33 §
38
42
44
45
48
52
56
63
68
25 §
29 §
32
35
38
40
41
43
45
46
49
51
25 §
29 §
31
34
37
39
40
43
46
49
55
59
25 §
29 §
33 §
40
44
45
47
50
54
58
65
69
§ = Span Limited by length to depth ratio of 24
NOTES: These overall spans are based on NDS
91 with 4" nominal bearing each end, 24" o.c.
spacing, a live load deflection limited to L/240
maximum and use lumber properties as follows:
2x4 fb =2000 psi ft=1100 psi E=1.8x106 2x6fb=1750
6
psi ft=950 psi fc=1900 psi E=1.8x10 . Allowable
Alpine Engineered Products
spans for 2x4 top chord trusses using sheathing
other than plywood (e.g. spaced sheathing or 1x
boards) may be reduced slightly. Trusses must
be designed for any special loading such as
concentrated loads from hanging partitions or air
conditioning units, and snow loads caused by
drifting near parapet or slide-off from higher roofs.
To achieve maximum indicated spans, trusses
may require six or more panels. Trusses with an
asterisk (*) that exceed 14' in height may be
shipped in two pieces. Contact your local Alpine
truss manufacturer or office for more information.
15