Replies

1. 
   mike_maines | Jun 21, 2008 01:52pm | #1

   Never tried that, but it would probably work just fine. 

   Biggest potential problems would be bowing out of the Azek if there's too much pressure from the concrete when it's poured, and differences between the three materials in moving with temperature and moisture swings. 

1. 
   woodpecker47 | Jun 21, 2008 02:48pm | #3

   thanks mike, if the pt post shrinks after the concrete has dried,would it be wobbly, but then all fenceposts would be loose. should i forget about the azek completly and try some other material. what's that stuff they used to make traffic sign with? some sort of plywood. azek is really expensive, 3/4" 4x8 sheet $ 165,-- now i'm really confused.

1. 
   Shep | Jun 21, 2008 06:06pm | #5

   The sign ply is MDO ( medium density overlay) plywood- basically a sheet of exterior ply with a paper face on it.

   My local yard has it for $77.60 for 3/4" finished both sides.

   A thought - instead of filling the void with concrete, would pumping expanding foam in work any better? The foam would, at the least, move and give a bit.

   Or just pack out the top and bottom of the 6x6 with PT to build it out to the proper dimension, slip the finish post over, and fasten it.

1. 
   dieselpig | Jun 21, 2008 07:58pm | #6

   Or just pack out the top and bottom of the 6x6 with PT to build it out to the proper dimension, slip the finish post over, and fasten it.

   Dats what I would do.  In fact that's what I did for my front porch columns.... they're about 7'6 or 8'.  I packed out the top, the middle, and the bottom to about 1/8" to a 1/4" shy of my inside finished dimension.  I think I just packed them out with one ring of Pt 2x4.   Built three sides, put it to the post (4x4 in my case) and set the third side.  Plumbed it up and nailed it off.  It's been about 2.5 yrs now and everything is still nice and tight.  Mine are pine but I've done it with Azek with similar success.

   Don't know that MDO would be the right material for a fence post either.  Too close to the ground.  I love the stuff in the right situation though.View Image

1. 
   Shep | Jun 21, 2008 09:19pm | #7

   Yeah, I wouldn't use the MDO for a fence post either, but the OP was asking about it. I should have included my reservations about using it so close to the ground.

   I'm just finishing a job where I wrapped a 4x4 post with tapered 1x pine- 9-1/2" 0n the bottom to 7-1/2" at the top, 7-1/2' tall. Gives it sort of a Arts & Crafts look. One row of blocking at the top, and one at the bottom gave it plenty of strength. I would probably use another row of blocking in the middle with Azek, tho.

2. 
   mike_maines | Jun 23, 2008 02:03pm | #9

   I usually just do what Shep does too, pad out the bottom of the post, slip the sleeve on, shim the top snug and nail or screw it all together.

   Azek is a great material for this application.  MDO is not.  I haven't liked the look of the pre-made vinyl covers I've used.

   Azek is expensive stuff.  By the board it doesn't seem as bad as by the sheet. 

1. 
   user-53014 | Jun 23, 2008 05:04pm | #10

   I second the filling with polyurethane foam option. I have used foam many ways to fill areas that need building out.

1. 
   mike_maines | Jun 23, 2008 05:07pm | #11

   Me too--

   Got in trouble when I used it to fill in the mortise on a bunch of salvaged doors though!

    

2. 
   Matt | Jun 21, 2008 02:16pm | #2

   I think you want some room for the dissimilar materials to move independently.  Azek that big could move quite a bit and we all know how crazy PT wood posts can act.

3. 
   Danno | Jun 21, 2008 03:54pm | #4

   You can buy ready-made vinyl "sleeves" that go over PT posts. They often recommend filling the bottoms of the sleeves with concrete--you could fill the whole thing. You may not like the look of vinyl though.

4. 
   Matt | Jun 23, 2008 01:40pm | #8

   Here is a piece of off-the-wall but related information....

   I once had some concrete guys use a ~5' azek board as a form on a vertical curb at the edge of a parking lot.  They didn't strip the form indelicately - just left it in place - which normally would have probably been OK.   The next day when they tried to strip the form it wouldn't come off so they just left it.  You would have thought that Azek is pretty slick and it would come right off.  Not sure what happened, but that piece of Azek was welded to the side of that piece of concrete as if it were glued in place with polyurethane construction adhesive or something.  A labor and I spent well over an hour chipping that board off the concrete with a wide chisel and hammer.  It was as if a chemical in the concrete had melted the azek and they had become one.