24x48 pole barn, need to pour slab first. 6x6's on top of slab?

[ovrszd]

My previous shop was a 6x6 post pole barn with concrete added. It burned. In cleaning the site for a new shop I had to remove the concrete and the post stumps. I cut the stumps into "block" length and still use them. No deterioration after 15 years of standing. In my country the posts have a life span longer than I do. In my country frost heave is the enemy.

I have a neighbor down the road a couple miles who's house foundation is treated lumber, no concrete. Go figure.....

 

[Larry Caldwell]

I was at a pole building place the other day and noticed some heavy duty steel 6x6 post holders. They basically look like a U shape as the saddle and a plate on the bottom for big bolts or anchors of some sort to bolt to the concrete. If I had a slab already I would use them. They looked like about 5/16 to 3/8" thick metal.

Yeah, just like that only different. :laughing: For new construction they come with the anchor welded to the post base so you just puddle them into the wet concrete. They become an integral part of the footing. With 6" of rebar sticking out on each side, you would have to rip up the footing for wind to lift the post.

 

[Larry Caldwell]

I think you have exposed the problem with traditional pole-barn construction, that being ground contact with wood. I think the old CCA wood was supposed to be good for 40 years but that is no longer an option around here and depending on soil I don't know if the 40 year thing worked anyway. I guess if one were to be able to sink posts deep enough and shield them from moisture top/bottom and all around they should last forever. Perhaps a concrete cookie on the bottom and the posts surrounded by large diameter pvc? Personally I'm glad I built on slab...I don't have to worry about ground contact of wood...a lot of lumber involved but it is all "high and dry". Will see if I can find the pix from the build.

The old penta treated wood was great, but they took it off the market because of environmental concerns and the fact that it occasionally killed barn builders. The new stuff, I think, is copper arsenate, which protects pretty good against fungus and bugs. I don't know about the new stuff, but in the old days we wrapped the posts in tar paper to keep it from contact with the concrete. I was told that the alkali in concrete would suck the treatment out of the wood. I think it actually turned the oils to soap and let them wash out.

 

[teejk]

The old penta treated wood was great, but they took it off the market because of environmental concerns and the fact that it occasionally killed barn builders. The new stuff, I think, is copper arsenate, which protects pretty good against fungus and bugs. I don't know about the new stuff, but in the old days we wrapped the posts in tar paper to keep it from contact with the concrete. I was told that the alkali in concrete would suck the treatment out of the wood. I think it actually turned the oils to soap and let them wash out.

I think what you describe as copper arsenate is the old treatment (CCA...chromium copper arsenic) might still be available for posts but as far as I know is no longer allowed for anything else (that arsenic thing). Kinda depends on soil I guess...we are pure sand/gravel here so drainage is not a big issue but I think if you are building in a clay environment I might want to shield the posts.

 

[ShowroomShine]

Never seen a pole barn built on top of the pads. Drive around the country and look at those old barns, especially really weathered & unused ones. The fact that they're still standing should be enough convincing for you especially how we've come a long way with the introduction of specially treated 6x6 made for in-ground applications. Raise the pole building and pour the slab afterwards. I used expansion joints around each uprights.

You guys are missing the point. I'm not pouring slab first because I'm concerned about wood rot, I need to pour the pad first because once my concrete driveway goes in, I dont want an 80,000lb concrete truck driving on it to get back to where the pad will be.

 

[teejk]

You guys are missing the point. I'm not pouring slab first because I'm concerned about wood rot, I need to pour the pad first because once my concrete driveway goes in, I dont want an 80,000lb concrete truck driving on it to get back to where the pad will be.

I plead guilty your honor! I missed the point. Your driveway should be of primary importance (and concrete takes a lot of time to cure). So back to your barn construction...if you aren't worried about rot, then I think I'd sink the posts (cookie on the bottom) and use them to anchor your concrete forms so you know you will be plumb, square and level. With your size a concrete truck should have enough chutes to get your slab poured and if it is merely a few posts they will be able to move the power trowel around with little effort. I don't think I'd trust the surface post anchors for a building that size unless you can brace all walls somehow.

 

[ovrszd]

Very common here to set the posts, add the bottom bottom treated boards around the edge holding the posts straight, then pour the concrete.

 

[EddieWalker]

You guys are missing the point. I'm not pouring slab first because I'm concerned about wood rot, I need to pour the pad first because once my concrete driveway goes in, I dont want an 80,000lb concrete truck driving on it to get back to where the pad will be.

Why build with posts if you are going to have a concrete slab done first? Why not just stick build the building like a house is built with studs?

 

[Reload5]

What happened to the good ol' days when we just augered two foot holes in the ground and used quickcrete with 4 x 6 treated posts?

 

[prichard]

Correct CC, we have all gone a bit off topic.

If I understood correctly you already have the pole barn kit?

There have however been several suggestions:
You could set the posts even if not boulding the rest of the barn.
You could exclude post locations from the slab.
You could do slab later with concrete buggies or pumper.
You could use pole supports cast into the slab.

I may have missed some