Originally Posted By: roconnor
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Thanks for the input from the woodworking point of view guys. Maybe the difference is the manufactured lumber is mass produced and under different stress in service, and they probably don’t use the top of the line expensive adhesives.
Manufacturers of glued wood products are not so quick to admit there have been problems unless pushed, but they will definitely tell you these products should not be exposed to moisture. Roof and exterior wall members that should note be exposed to moisture ... hmmmmm ... but we all know what the reality is ... ![icon_eek.gif](upload://yuxgmvDDEGIQPAyP9sRnK0D0CCY.gif)
Glu-Lams actually don't hold up very well in high moisture conditions, and if there are interface problems there can be significant strength loss. One of the reasons LVL lumber (e.g. Microlams) were developed, which really doesn't rely on glue to resist stresses ... it mostly holds the laminations together (like a stack of paper on its side held together).
But even LVL's are not recommended for moist conditions, and these members have been damaged when the building wasn't enclosed/covered right away leaving it exposed to the weather, or where a roof leaks. This moistly just causes cupping and swelling on LVL's, but has caused glue interface problems. Thats why LVL's that will be exposed during construction are recommended to have a waterproof barrier (e.g. "Watershed" overlay for the Microlams), which I recommend for any LVL.
One huge disadvantage with the finger joined studs is that the glue lines are also under stress in exterior wall studs when subjected to wind loads. This combined with the likelihood over time of the members being exposed to moisture and past problems with glued structural lumber makes me stop and really think about these products.
I am not saying they are bad, but as an engineer also I am looking at them with a skeptical eye for now due to the past problems. Maybe the manufacturer's have gotten better with the adhesives they use and ensuring a good bond on these finger joined members ... but I think only time will tell, and why I say the "Jury is Still Out" ...
Just my 2-nickles ...
Robert O'Connor, PE
Eagle Engineering ?
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I am absolutely amazed sometimes by how much thought goes into doing things wrong