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RE: 3X Plates and Washers on Intermediate Anchors

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As at least one person pointed out, wood does not shrink much in the
longitudinal (i.e. parallel to the grain) direction.  The overwhelming
majority of wood shrinkage is in the cross section either in the radial
directions relative to the wood's growth rings (i.e. the cross section
wants to get smaller) or in the tangential direction relative to the
growth rings (i.e. the circumference [sp?] wants to get smaller and thus
checks and splits open up).  So, for your sill plant, the hole in the
longitudial direction (i.e. the direction of the applied shear force)
should change very, very little due to shrinkage.  In the other direction,
I would envision that it would not change the hole size too much either as
overall the cross section would want to reduce which would cause the side
edges of the hole to want to move toward the center of the hole, but could
be compensated by the amount of wood between the edge of the hole and the
edge of the sill plate reducing...but I believe that most shrinkage acts
such that the movement is towards the center of the wood cross section,
especially if that wood member was cut from pretty much dead on the center
(heart) of the tree.

As a side note, I would believe the big issue with regards to not placing
the nuts and plate washers would be overall uplift on the wall.  If there
is net uplift, then those anchor bolts would be all that in theory
prevents the house from flying off to Oz.


Adrian, MI

On Thu, 2 Mar 2006, Gerard Madden, SE wrote:

> My first instinct was to think that the free edges of the wood move
> toward the fibers behind it, the wood contracts when the water escapes
> making the hole larger because those extreme fibers around the edge of
> the hole are moving back to where there is more wood. I guess what your
> saying is that the edges of the sill are shrinking at a greater rate
> than the hole, that the overall shrinkage of the sill is such that it
> surpasses the shrinkage of the hole fibers making the end result a
> smaller/tighter hole diameter.
> Sound right?
> -gm
> -----Original Message-----
> From: Garner, Robert [mailto:rgarner(--nospam--at)]
> Sent: Thursday, March 02, 2006 10:51 AM
> To: seaint(--nospam--at); gmadden(--nospam--at)
> Subject: RE: 3X Plates and Washers on Intermediate Anchors
> Another analogy that helps visualize the shrinkage:  When you install a
> ring gear on a flywheel, you heat it up to expand it, slip it onto the
> flywheel, and when it cools, it shrinks in place and clamps the
> flywheel.
>   _____
> From: Rhkratzse(--nospam--at) [mailto:Rhkratzse(--nospam--at)]
> Sent: Thursday, March 02, 2006 10:46 AM
> To: gmadden(--nospam--at); seaint(--nospam--at)
> Subject: Re: 3X Plates and Washers on Intermediate Anchors
> Wouldn't the holes *shrink* if the entire piece of wood shrank (shrunk?)
> as it dried?
> Ralph
> In a message dated 3/2/06 9:26:18 AM, gmadden(--nospam--at) writes:
> with shrinkage, the holes size will increase over time
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