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Roof reports and MinimumDead Load Questi

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Dennis,

I pulled out TPI-68, -74 and -85 (which I should have done before my prior 
post) and in Appendix A, they have,

Top chord dead load:  actual weight but not less than **7 psf**.

Bottom chord dead load:  actual weight but not less than 10 psf.

Accessible attics by means of scuttle:  Bottom chord minimum total 
load is 10 psf. (TPI-85)

With regard to the truss plates of the early '70's and late '60's, The "Gang 
Nail" (TM) truss plates had much longer nail type protrusions than the type 
does now.  These would have the elongated punch-outs.  "Gismo Gussets" (TM) 
had octagonal punch-outs (looks circular) and the triangular prongs were 
barely 3/16 inch long.  While some plates were designed to have some nails 
hold them temporarily in place while they were pressed or rolled into the 
wood, they would not have been nailed.  If the plates are actually nailed, 
then the truss probably would not have been built under the plated truss 
industry standards, so it would be unknown what dead loads were used in the 
design of the trusses.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Dennis Wish wrote:

. > Dennis S. Wish PE
. > seaintonln(--nospam--at)aol.com

. > Thanks for the comments about roof loads and minimum dead loads. Roger 
. > Turk's comments were pretty much dead on to what I was looking for. As 
. > far as replacment weight - I restricted the roof to a 6.0 psf tile and 
. > required the contractor to provide an approriate ICBO report from the 
. > manufacturer of the tile to verify the weight before installation. 
. > Regardless of the Shake weight, the lightweigt tile (6 psf) and the 
. > existing 1/2" thk plwd (and builders paper) would not exceed 10 psf at 
. > the top chord. I had read someplace that the weight of green shake is 
. > typically used in the design dead load and that this can very from 3.0 to 
. > 5.5 psf. 

. > Roger, you brought up the plates used on the trusses - a very good point. 
. > I did inspect them and found them all to be no less than 6x6 oversized 
. > press plates. I'm not sure how much they were used in the early 70's but 
. > do know that they are more the standard now. They could have been nailed 
. > plates, but my eyes are not what they were and I could not make out the 
. > nail heads.

. > Even though I posted this questions, I have had to deal with this issue 
. > for years. I've always considered my alternatives to be conservative and 
. > when the truss looks particularly flimsy, I'll recommend analysis of the 
. > truss or replacement with a similar weight material regardless of 
. > appearance.

. > Thanks again for all the help,

. > Dennis