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-   -   Building on piers & pressure treated posts, or just concrete piers? (http://www.diychatroom.com/f19/building-piers-pressure-treated-posts-just-concrete-piers-70751/)

TinaRap 05-07-2010 05:55 PM

Building on piers & pressure treated posts, or just concrete piers?
 
I'm building a 12x24 art studio. The local builder wants to build on concrete piers (2.5 ft deep) with pressure treated wood posts sticking up. Soil would be piled back up against these posts. Although I will install a french drain around this building, I'm concerned (in inexperienced) that in time the pressure treated wood may rot - whereas concrete piers won't. I don't want to have to fix this 20 or 30 years from now, when I'm in my old age! I just want an economical art studio. Any suggestions? I've scoured the blogs already. Thanks!

kwikfishron 05-07-2010 06:06 PM

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Originally Posted by TinaRap (Post 438965)
I'm building a 12x24 art studio. The local builder wants to build on concrete piers (2.5 ft deep) with pressure treated wood posts sticking up. Soil would be piled back up against these posts. Although I will install a french drain around this building, I'm concerned (in inexperienced) that in time the pressure treated wood may rot - whereas concrete piers won't. I don't want to have to fix this 20 or 30 years from now, when I'm in my old age! I just want an economical art studio. Any suggestions? I've scoured the blogs already. Thanks!

Wow, posted same pic. twice in 24hrs.

He can go down 2 1/2' with this.

TinaRap 05-07-2010 06:08 PM

Yes, this photo is terrific, but the builder has proposed burying the post IN the concrete for stability over the long term. What do you think of that?

kwikfishron 05-07-2010 06:14 PM

I think we are right and he is wrong.

Print the picture, show him and say "if you can’t do it I’ll find someone that will".

jogr 05-07-2010 07:59 PM

Unless your studio is going to have a dirt floor I'd go with a floating slab. A slab isn't going to cost more than adding a wood frame floor to a pole building.

Willie T 05-07-2010 08:13 PM

It is never a good idea to sink wooden posts in concrete. If you must do so, make sure that the bottom few inches of the hole are gravel so that any water that goes down alongside the post (and it WILL get down between the post and the concrete) has a way to drain out.

Water and wood = mold.... which is ROT.

TinaRap 05-08-2010 09:33 AM

What about sinking the post in concrete, but having the top of the concrete several inches above ground?

kwikfishron 05-08-2010 09:44 AM

I would want the post on top in a bracket. Wood will rot, even PT. If you ever had to deal with the post again it would be much easier to replace sitting on a bracket than a post entombed in concrete.

TinaRap 05-08-2010 10:34 AM

Thank you so much. I will continue the discussion with the builder. It does seem it would be quite a bit less expensive to do pier/post than slab, so I'm leaning towards that. I appreciate everyone's input.

Daniel Holzman 05-08-2010 12:55 PM

Currently available PT lumber uses quaternary copper (quat) rather than the old CCA method. The new type of PT lumber tends to attack most forms of steel, and requires different types of brackets and fasteners. In particular, the metal support posts MUST be rated for direct contract between the PT lumber and the metal.

Similarly, the fasteners must be designed for use with PT lumber. To the best of my knowledge, certain forms of stainless are OK, and specific types of galvanized are OK, most everything else is NOT OK. In general, it is a very good idea to elevate the post above the concrete to prevent rotting of the post due to contact between concrete and the post, even for PT, just make sure the brackets and fasteners are specifically designed for use with the particular type of PT lumber you are using for the post.

TinaRap 05-08-2010 01:06 PM

Thanks Daniel, I appreciate this information. To be sure I understand, you are advocating NEVER burying PT posts in concrete (if you're interested in longevity), whether you are in a dry spot (there'll be a french drain and skirting on the bottom) or not?

If I've got it right, you are not concerned about stability (leaning, sway) of the PT posts/building? Can you explain how these brackets attach to the concrete and PT posts simultaneously so I can understand their structural superiority?

RoyalAcresRod 05-08-2010 01:30 PM

Tina, neither the builder or you will save any money or time by burying the post in concrete, where over the long term, the part of post encased in concrete, not can, but will eventually fail.

Using the recommended bracket method, the wood will remain above ground, contributing to a much longer life, as it will have the ability to dry out, and will be further away from wood-destroying organisms.

Either way, a concrete pier will have to be constructed. The only additional cost will be the proper brackets, as described above. And that cost may be offset by smaller posts, or no posts if the beams sit right on the brackets.

Simpson, one of the leading bracket manufacturers, has quite a bit of literature on the correct brackets to be used with the new PT wood. That info is available on their website.

Listen to the experts above..they all giving you the straight scoop. I believe your builder is one of those folks who live by the mantra of, "This is the way I've always done it."

His method will of course work.....but can never be as long-lived as the bracket method.


Rod

Daniel Holzman 05-08-2010 02:12 PM

There are many different styles of brackets that can be used. As noted by previous poster, Simpson makes many different brackets specifically designed to support wooden posts. The brackets are typically nailed to the posts through predrilled holes in the bracket, and are attached to the concrete in various ways, mostly depending on whether this is a retrofit (i.e. the concrete support is already in place), or a new installation.

In the case of a new installation, the bracket has a post designed to be embedded directly in the concrete. Note that this is a galvanized post specifically rated for long term direct contact with concrete. In the case of retrofit, the bracket is attached to the concrete using either expansion type anchors, epoxy anchors, or threaded connections.

There should be no issues with lateral stability of the post so long as the appropriate bracket is used, the correct fasteners are used, and proper installation technique is observed. If your builder is unfamiliar with proper installation technique for these types of brackets, I suggest you consider a different builder.

TinaRap 05-08-2010 03:00 PM

Thank you all so so much!


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