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Hem Fir (N) Design Value Reductions

bIockhead

bIockhead

Structural
Jun 14, 2022
16
I saw this notification (reference: https://www.sbcacomponents.com/medi...e-reductions-approved-by-alsc-board-of-review) and was wondering if anyone had any insight into the rationale prompting this. It can't be that big a deal if no issues were flagged for existing structures designed using the old strengths (right????).

Does this simply reflect changes in the representative properties where maybe higher scatter in the testing data is being observed? Would be nice to see some reasoning beyond "
changed as part of the routine monitoring and assessment process".

When the notification email includes "Hem-Fir (N) remains a trusted and dependable choice for residential and commercial construction" then I reflexively become suspicious.

Curious whether anyone here knows the basis for this.
 
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This sounds alot like the So. Pine value reduction back in 2013. At the time the design value change (pretty significant reduction) was attributed to a "change in the resource mix" for Southern Pine (i.e. age and specific tree type that is being harvested and lumped into the "Southern Pine" Mix.) I believe the reduction was based on standard quality assurance testing of the visually graded lumber itself by grading agencies.

My assumption is that a similar process is ongoing for Hem-Fir, and other species may follow depending on changes in harvesting practice for that particular species.

At the end of the day I wonder if younger and easier to grow trees are being harvested due to modern timber practices - More juvenile wood = lower design values. This is purely speculation thought so take it with a grain of salt..
 
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RWW0002 said:
At the end of the day I wonder if younger and easier to grow trees are being harvested due to modern timber practices - More juvenile wood = lower design values. This is purely speculation thought so take it with a grain of salt..
Click to expand...
I asked AWC a similar question a few years ago regarding old vs new wood values and they did say that main driving factor is how the testing is performed, but that also younger wood being used today vs in the before times was a consideration as well.
 
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