How to calculate truss dead load in PSF?

[Busybardo]

I am working on a project where we are using wood trusses (2x6 for top and bottom chord, 2x4 for web). I am trying to figure out a psf from the weight of the truss but am hitting a road block. I have attached a picture of my attempt. Any help here would be much appreciated. I use a 44pcf for wood to be conservative. Thanks!

 

[ToadJones]

determine the weight of your truss, divide by the length, and that will give you the weight of the truss in pounds-per-foot (PLF).
Divide that number by the truss spacing = PSF.

 

[dik]

2x6 are approx 2.5# per foot... and using a factor of 3 for top chord, bot chord and web... you would have load of approx 7.5# per foot... and, at 2' centres approx 4 psf of area. Check with a local supplier.

Dik

 

[woodman88]

2x6=2.3psl, 2x4=1.5psl at 40 pcf lumber
slope factor (slope length divided by run length)
0:12=1, 5:12=1.1, 12:12=1.4 (rise : run)

Assume a 5:12 roof, flat ceiling

TCDL(slope factor)+ BCDL + 1.5(slope factor) WebDL = truss psl
2.3(1.1) + 2.3 + 1.5(1.1)1.5 = 7.3 psl at 2'o.c. = 3.7 psf

Garth Dreger PE
AZ Phoenix area

 

[MiketheEngineer]

Lumbermate - now Alpine Engineered Products has a booklet "Encyclopedia of Trusses". It has many great tables supplying all kinds of info like this. See if you can get yourself a copy. I think it is Alpeng.com - but they have been bought by ITW - so you might need to go there.

 

[steelbeam]

The truss will weight about 6.9 lb./ft or 3.5psf @ 24" centers. I got this out of tables in "Wood Engineering and
Construction" 3 rd Ed. Faherty and williamson.

 

[rscassar]

I don't design roof trusses but I use 4psf when considering gravity loads on framed walls and 2psf when design tie-down. As for the calculations, calculate your total length of 2x6 and total length of 2x4, convert these to total weights, multiply by 1.05 to account from nail plates and divide by the length of and spacing of trusses.