Roof Truss Span Tables

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.

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