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Re: glulam shrinkage

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Daryl-

Of course timber products are affected by changes in moisture levels  but I assumed (I hope correctly) that David's inquiry was related to "shrinkage".... that phenomena normally considered to occur from moisture levels at construction to moisture levels once the timber is acclimated.

One of the major benefits of "engineered timber" is that it comes from the factory pretty dry already and shrinkage to acclimation is minimal ....nothing like green sawn timber to acclimation moisture levels.


The shrinkage (or variation of size due to changes in moisture) due to changes in local relative humidity would be pretty small unless you've got an unprotected glulam installed in an exposed outdoor application.

imo dimensional changes due to  relative humidity changes have to be a pretty much 2nd order effect for most applications

fyi   I did an experiment to definitively prove that holes drilled in green timber got smaller when the timber dried (obvious to me but not the guy on the other side of the bet)

In order to generate "green / fully wet timber"  I sprayed 2x4 chunks everyday for a week.....no dice.

I wound up submerging them for 3 weeks to get them above the moisture.level above 26% (often the level for green timber)

It's pretty hard to drive up moisture levels through incidental moisture contact....you need pooled water for extended periods and  an adverse surface to volume ratio.

cheers
Bob




On 8/17/07, Daryl Richardson <h.d.richardson(--nospam--at)shaw.ca> wrote:
David, Robert,
 
        Actually, a gluelam may increase or decrease in volume with changes in moisture content.  This may be affected by the relative humidity on the environment where it is located.
 
        Just don't ask me how much.
 
Regards,
 
H. Daryl Richardson
----- Original Message -----
Sent: Friday, August 17, 2007 6:57 PM
Subject: Re: glulam shrinkage

Being engineered timber fab'd from KD lumber I would expect close to no shrinkage

APA link

http://www.apawood.org/glu_level_b.cfm?content=prd_glu_bui_floors

cheers
Bob

On 8/17/07, David Topete <dtopete(--nospam--at)gfdseng.com> wrote:

How much shrinkage is expected of a glulam beam?  Any ideas?

David A. Topete, SE