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RE: Powder Post Beetle Deterioration

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Depending on how long there has been activity there could be major deterioration of the wood.  When they did the repairs 25 years ago, did they treat the structure to kill the insects?  Have there been inspections to make sure they have not come back?  This includes inspecting the other trusses.  The powder post beetles eat/tunnel through the wood and are often unnoticed.  The only evidence is small piles of sawdust where there is activity.  I have seen wood members that look perfectly fine on the outside, but completely eaten on the inside.  On very close inspection you might fine small pin holes into the wood.  But you are not aware of the tunnels on the inside.  We typically take a very small diameter drill bit and drill through the member and see what kind of resistance there is.  We drill several holes – every 18 to 24 inches.  That will tell how much damage has been done.

 

Gary W. Loomis, P.E., Senior Structural Engineering

Master Engineers and Designers, Inc.

-----Original Message-----
From: jeff.giger(--nospam--at)metso.com [mailto:jeff.giger(--nospam--at)metso.com]
Sent
: Monday, June 18, 2007 9:31 AM
To: seaint(--nospam--at)seaint.org
Subject: Powder Post Beetle Deterioration

 


Our church has powder post beetles in the bottom chord of the wooden post-beam construction.  The church is 160 years old and in good structural shape other than the roof structure.  It has been decided to replace the entire roof structure with conventional trusses in October, before the snow flies.  The church wants me to do an structural evaluation of whether the structure is safe now at the current condition.  I found out 25 years ago a cable/bottom chord wooden reinforcement was performed on this one post & beam support.  I can do all the analysis, but the bottom line is going to be, how deteriorated is the beam.   We are going to talk again to a "post-beam construction expert" (contractor who is doing the roof replacement and has alot of post-beam construction experience) to get his opinion on the wood beam condition.  
Any past experience/input would be greatly appreciated.

Thanks,

Jeff Giger,  P.E.
Buckhorn Methodist Church, PA