Alpine

12' 6" Roof Truss Span Tables 9 Top Chord 2x4 2x6 2x6 2x4 2x6 2x6 2x4 2x6 2x6 2x4 2x6 2x6 Bottom Chord 2x4 2x4 2x6 2x4 2x4 2x6 2x4 2x4 2x6 2x4 2x4 2x6 Pitch Spans in feet to out of bearing 2/12 24 24 33 27 27 37 31 31 43 33 33 46 2.5/12 29 29 39 33 33 45 37 38 52 39 40 55 3/12 34 34 46 37 39 53 40 44 60 43 46 64 3.5/12 39 39 53 41 44 61 44 50 65 47 52 70 4/12 41 43 59 43 49 64 46 56 69 49 57 74 5/12 44 52 67* 46 58 69* 49 66 74* 53 66 80* 6/12 46 60* 69* 47 67* 71* 51 74* 76* 55 74* 82* 7/12 47 67* 70* 48* 72* 72* 52* 77* 77* 56* 80* 83* 2/12 24 24 33 25 27 38 27 31 41 29 32 44 2.5/12 28 29 40 29 32 43 31 37 46 33 37 49 3/12 30 33 45 31 37 47 34 42 50 36 42 54 3.5/12 33 37 49* 34 41 51* 36 46 54* 39 46 58* 4/12 35 41 52* 36 45* 54* 39 50* 58* 42* 49* 62* 5/12 38* 47* 57* 39* 51* 59* 42* 56* 63* 45* 54* 68* 6/12 - 2/12 ‡ 40 43 59* 42 49 62* 45 56* 66 48 57* 71* 6/12 - 2.5/12 ‡ 37 38 52 38 44 57* 41 50 61* 44 52 66* 6/12 - 3/12 ‡ 33 33 45 35 38 52 38 43 56* 40 46 60* 6/12 - 3.5/12 ‡ 28 28 38 32 32 44 34 37 50 36 39 54 6/12 - 4/12 ‡ 22 22 31 26 26 36 30 30 41 32 32 44 ‡ 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 Top Chord 2x4 2x6 2x6 2x4 2x6 2x6 2x4 2x6 2x6 2x4 2x6 2x6 Bottom Chord 2x4 2x4 2x6 2x4 2x4 2x6 2x4 2x4 2x6 2x4 2x4 2x6 Depth Spans in feet to out of bearing 16" 23 24 25 § 25 § 25 § 25 § 25 § 25 § 25 § 25 § 25 § 25 § 18" 25 27 28 27 27 29 § 29 § 29 § 29 § 29 § 29 § 29 § 20" 27 28 30 28 28 32 31 30 33 § 32 31 33 § 24" 29 30 33 31 31 35 34 33 38 35 34 40 28" 32 32 36 34 33 39 37 36 42 38 37 44 30" 33 33 38 35 35 40 38 37 44 40 39 45 32" 34 34 39 36 36 42 39 39 45 41 40 47 36" 36 36 42 39 38 45 42 41 48 43 43 50 42" 39 39 45 41 41 48 44 44 52 45 46 54 48" 40 42 49 43 44 52 46 47 56 46 49 58 60" 44 47 55 46 49 58 48 53 63 49 55 65 72" 45 51 60 48 54 64 51 57 68 51 59 69 § = Span Limited by length to depth ratio of 24 A l p i n e t r u s s d e s i g n s a r e engineered to meet specific span, configuration and load conditions. The shapes and spans shown here represent only a fraction of the millions of designs produced by Alpine Engineers. Total load(PSF) Duration factor Live load(PSF) Roof type 55 1.15 40 snow shingle 55 1.15 30 snow tile 47 1.15 30 snow shingle 40 1.15 20 snow shingle 40 1.25 20 ** shingle **construction or rain, not snow load 55 1.15 40 snow 47 1.15 30 snow 40 1.15 20 snow 40 1.25 20 rain or constn. Total load(PSF) Duration factor Live load(PSF) NOTES: These overall spans are based on NDS '01 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 f =2000 psi f =1100 psi E=1.8x10 2x6f =1750 psi b t b 6 f =950 psi f =1900 psi E=1.8x10 t c 6 . Allowable 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 Alpine truss manufacturer for more information. 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. 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.

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