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RE: Fixed base timber column

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Use a bigger caisson I would suggest a 24" dia.  
1.  Form a 14" dia recess in the center of the caisson all the way through
to the soil below
2.  Place about 12" minimum of clean crushed rock in the base
3.  Install lag bolts in the side of the 10 x 10 timber sufficient to
transfer the moment into the concrete caisson leaving the heads about 1/2"
away from the face of the wood
4.  Place the 10 x 10 into the caisson
5.  Add about 3 inches of rock around the base of the 10 x 10
6.  Shim column to plumb
7.  Grout the space between the caisson and the 10 x 10 which will encase
the lag bolt heads.
8.  Tool a 1/4" wide x 1/2" deep recess around the perimeter of the 10 x 10
9.  After the grout cures, install a backer rod & sealant around the

The base should be treated, and the concrete should slope away from the

The advantages are: drainage at the base to avoid rot, lags can transfer the
forces without relying on bond, lags can transfer the forces regardless of
seasonal wood shrinkage and swelling, and for my favorite reason it is
simple, quick, easy ,and cheap.

Harold Sprague
The Neenan Company

> -----Original Message-----
> From:	Thomas Long [SMTP:tomlong(--nospam--at)]
> Sent:	Wednesday, January 20, 1999 08:00 am
> Subject:	Fixed base timber column
> Importance:	High
> I am designing a free standing trellis.  The footprint is about 100ft x
> 20ft.  The owner wants to use 10x10 timber columns, 10x12 beams with 4x8
> lattice at 36" o/c.  The columns are founded on 18" diameter caissons.
> The
> timber columns are spaced at 14'-0".
> The owner would not like to see the typical knee braces to support the
> timber frame from lateral movement, and no exposed connections.  I have
> been
> tossing ideas around in my head about how to approach this fixed base
> timber
> column condition.
> The ideas I have come up with are:
> 1. Use a vertical steel plate in the center of the column and bolt through
> and plug the holes.  I do not feel to good about this.
> 2. Embed threaded rods into the concrete either when they pour the
> caissons
> or then drill into the column and install with epoxy adhesive.  Not a bad
> solution, but how do I design it.
> 3. Embed a 2" +- pipe column into the concrete and drill the column and
> then
> bolt through and plug.  Hard to drill into the timber and to construct.
> Has any body designed a structure like this and if there is, how did you
> do
> it, what is the best solution.
> Thank you in advance.
> Thomas Long
> Thomas Long Engineering