# truss lift



## maj (Mar 13, 2006)

Joasis, I would think if you have a history of no problems with uplift because of the dry climate and mild winters, you should be able to get by doing things as you normally would. But don't take my word, I only know what works for me! On the other hand, a 44' span does have the pssibility to be more susceptible to movement. The scissored vault should be dealt with carefully. That is still a problem for me sometimes. Seems I always get cracks somewhere on a scissored vault.

Here's a good simple explanation and how to deal with the problem.
http://www.rushwood.ca/trussuplifting.html


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## Joasis (Mar 28, 2006)

I probably will frame the vaulted room after the trusses are in place, and then "load" the bottom with the wall, since from an engineering point, that artificially "breaks" the truss loading. I would guess the weight combined with sheetrock load will prevent uplift, since a scissor truss is less succeptable from my reading. There may be some timber beams placed if my customer can find oaks long enough for me to mill for them.


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## durham (Apr 17, 2006)

truss uplift is the result of internal upward stresses within a truss.
i.e. - winter conditions. Top chord exposed to colder temps than bottom chord ( which is covered by insulation. ) 
- wood shrinkage/relative humidity of wood
Maj is right on the money in his observations. Use those t clips & blocking. No screws in sheetrock within 18" of intersecting partion.


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## Dan K (Oct 14, 2005)

jjtt said:


> ...My question is: Should I have known not to attach any sheetrock to trusses within in 18" of interior walls, is that the sheetrockers responsibility, or is truss uplift not a common enough thing for a contractor to know everyway to avoid it( I have been building houses since 1998 and have never had this problem or heard of it.)



Ok,
I'm gonna go out on a limb here with my first post...I don't want to offend anyone but the answer to your questions is YES, any contractor should be aware of truss uplift.

Its defintitely more of an issue in northern colder climates... but bottomline... if your going to build with trusses you should know how they can react to seasonal changes...there's plenty of available documetation on this. I recently built my first home in Oklahoma and was shocked that the GC wasn't aware of uplift. I recently relocated from Illinois so I was aware of the potential problem. 

Respectfully,
Dan K


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## Joasis (Mar 28, 2006)

I am in Oklahoma Dan, and I haven't heard of problems with trusses til the last few years...Coming from Illinois, you would have had much more exposure then here. I talked to a buddy from Houston, and he was well aware of it. Talking with a few other carpenters here, some knew, some had never seen it. I asked the engineer at Mills Truss in OKC about the potential lift in the scissor (vault) trusses we will be using on the custom home, and he doubted it would be a factor, simply due to the average humidity here year round.


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