Replies

1. 
   CapnMac | May 22, 2007 05:23am | #1

   I cannot imagine, at least in my climate, any reason, let alone any advantage to a below-grade post to pier connection.

   Locally, I try to get wood verticals at least 8" above grade, and where that's not possible, to use galvanized tube in concrete to keep any wood out of our too-moist soil.  (There's an additional economy, in not needing 10' or 12' posts, that will likely rot at the ground joint no matter how detailed, the olny difference being in which year the rot occurs.)  Or, set the sonotubes that high, or what ever keeps the wood away best.

   Occupational hazard of my occupation not being around (sorry Bubba)
2. 
   Piffin | May 22, 2007 02:05pm | #2

   We do not want the wood down in the round so it stays drier, even though we use ground contact PT for these posts.

   We try to keep out crete no more than a few inches above finished grade both for appearance and because the crete seems to wick the cold down deeper into the soil. That is the local mythology and standard anyway

    

    

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   Taunton University of Knowledge FHB Campus at Breaktime.
    where ...
   Excellence is its own reward!

3. 
   woodchuckc | May 22, 2007 04:38pm | #3

   I know that the standard response is not to bury PT posts, and it seems logical. I just finished tearing down my deck that was 21 years old, with 4x4 PT posts buried about 16" deep and a "collar" of concrete around the top 6-8" of the buried part that had about 1" of soil on top (no, I did not build the deck - I inherited it with the house). This goes against everything you hear and read about how to set posts, but there was no evidence of any rot or decay of the posts - in fact, the buried part was in much better shape than the above ground part. I even took a sledge and broke the concrete collar off of the posts, and the wood there looked like new. The buried part was wet, but not saturated and resembled brand new PT wood. I definitely do not live in a desert somewhere; we get 45-50" of rain a year here in middle TN.

   I am not endorsing this method of setting posts, but I just thought I would provide a real-life example that seems to go against the conventional wisdom.

1. 
   Matt | May 22, 2007 04:55pm | #4

   Maybe the concrete "collar" was poured after the posts and footers were set and therefore the connection between the collar and footer weren't "waterproof"?

1. 
   woodchuckc | May 22, 2007 05:09pm | #7

   There were no footers - apparently the holes were dug, the posts set in, some dirt shoveled in around the bottom 10-12" of the post, and a concrete collar poured on top of that. I couldn't really even tell if they had put a layer of crushed rock or gravel in the bottom of the hole before setting the post in.

1. 
   Matt | May 22, 2007 05:57pm | #8

   Oh - OK, I gotcha.  My idea stands though - the posts had drainage from below so they didn't rot out.  Granted they had little to no support, but I guess it lasted OK because the soil was quite firm.  I think the thing is though that if the concrete encases the entire bottom section of the post, on 5 sides, that causes rot because it holds the water to the post.

   The way you describe is the way many/most fences are built.  Fence posts get lateral wind (etc) loads but little vertical loading like deck posts do. 

2. 
   JDRHI | May 22, 2007 05:03pm | #6

   Built my Mothers deck about 20 yrs. ago. Set my posts in the wet concrete piers at or about grade. Thats how I learned.

   I've since learned otherwise, and set my piers a good 8" to 10" above grade and attach posts with the proper connectors.

   I check the deck regularly however, and have yet to see any signs to cause concerns.

   Aint the right way.....but it worked.

   Owning a house that's over 100 yrs. old, I've also learned that quite often, the "right way" isn't the only way. The 2 X 8 rafters spaced 24" OC without a ridge being case in point.

   Not that I'm advocating any of the above.

   J. D. ReynoldsHome Improvements

    

    

3. 
   Piffin | May 24, 2007 12:35pm | #9

   that is because it was only a collar ands could not trap water.It also worked to keep bacteria and oxygen form working on it in that most active area just subsurface.But doing that here in cold climate and wet soils could make it more likely for frost to heave the post 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

1. 
   woodchuckc | May 24, 2007 04:36pm | #10

   Yep, it would definitely cause problems to do something like this up north. The deepest I've ever seen the ground frozen here is about 4", which is less than the depth of the concrete that was around those posts. I'm originally from Michigan, where we certainly couldn't get away with doing the things that get done here in Tennessee.I must admit, I do like the sturdiness and racking resistance provided by buried posts, especially with elevated decks. I know that attaching posts to poured footers above ground with the proper connectors and designing a deck properly from a structural standpoint make for a good and solid deck, but to me it is just more straightforward to build a solid, sturdy deck where the posts are buried a couple of feet in the ground with a solid base underneath them (where conditions allow it).I just built my replacement deck for the old one I tore down. I tend to overbuild things; it is only 12' x 24' and elevated about 5' above grade. It is attached to the house with a 2x10 rim joist and has a middle beam and outer beam (each beam is 2 2x12's nailed together) running the length of it with 4 6x6 posts under each beam, and 2x8 joists on 16" centers. I just got done screwing down the 1x6 ipe decking last weekend, and there is absolutely no deflection or movement of the deck. I used stainless joist hangers, nails and screws throughout. Outside of a little maintenance every couple of years, I'm anticipating it will last me as long as I will need a deck (I'm 48, so 30 years or so I hope).

4. 
   Matt | May 22, 2007 04:57pm | #5

   Are you talking about the post connection to the footer concrete?