Dry vs. Wet Pour Concrete For Pole Barn

[Tim Frank]

Re: Dry vs. Wet Pour Concrete For Pole Barn

I've pried many a 4 x 4 fence post root out of the ground that was set with dry concrete mix. You couldn't convince me that the drymix does not absorb sufficient moisture to harden up.

Heck, just leave an unopened bag of redimix on the floor of your garage for a year, then go back and try to pour it. And that bag was never even in the ground, having received a soaking like it would be for your barn supports.

A sure sign of the Apocalypse...Wizeone and I agree on something...
An annual rite of spring for me at the cottage is getting rid of a bag or two of various types of cement that have set over the winter into a solid block. I use it to fill potholes in the gravel road, and breaking it up with a sledge into small enough chunks to use as fill takes some real effort.
Whoever it was that said it doesn't set strong is welcome to come and help break it up this year...

 

[jameskb2]

Re: Dry vs. Wet Pour Concrete For Pole Barn

Hello!

I have been a building contractor for twenty years. I'd like to add my perspective if I may.

The purpose of the concrete at the bottom of the hole, as mentioned, is for footing. It assures the post will not compact the soil below it due to loads from the building and it's contents and use. (Live and dead loads) Pole barns typically rely on the depth of the pole in the ground, their frequency in spacing (4' apart, 6' apart ect.) and the building's sheathing / bracing for lateral loads. (Wind, you leaning something against the structure ect...)

I have built several barns, and know some specialty "only pole barns" guys. One thing to consider here is soil type, (how easily compacted?) and also it's porosity and water content. (How fast water passes through it, what time of year and how wet the soil is) Obviously sand has different load capacity than gravel, or rock. Clay has various degrees of bearing depending on how organic it is. Let's assume your soil is capable of handling the loads, (good sand / gravel mix....)

So, that being said, I have used the (now) code required method. Dig or bore the hole (a bobcat auger is a Godsend) to 6" below frost depth. Take a 4 X 4 x 8' or 10' post and COMPACT the soil at the bottom of the hole until it feels solid. Pour 80 to 120 pounds of dry gravel mix into the hole. Take the 4 x 4, and COMPACT the dry mix by lifting and pounding into the mix. Do so until it's quite firm. THEN, take a precast "button" (usually 12 to 14" in diameter) and drop it into the hole on top of your now tamped dry mix. Take said 4 X 4 post and tamp the button down flat. You'll know it's right, cause that 4 X 4 will now want to bounce off it.

Set your posts by either lifting them straight into the air and dropping them, or back the hole with a board and lift one end while the other slides along the board on the hole's side (preventing dig in or wall collapse of the hole) until it's up. Then back fill with NO organic earth (topsoil) Use the soil from whence it came (top soil goes on top). While back filling the post, check it for position and plumb. You should fill with 6" to 8" of soil, then TAMP the soil with a 2 x 4 around the post. Add 6" to 8" more and tamp again. You can tweak the post's position for the first tamp by compacting one side of the post first. Also, tamp (compact) the soil during back fill by working from post out to hole's edge. Once the soil's all used from the hole, you should have a "cone" of soil around the post. You can still tweak the post here, by pulling it to one side or the other to make it plumb, then stomp on the "loose" side with your foot. Then brace it with angled bracing tied to scrap 2 x 4 stakes driven into the ground and LEAVE IT ALONE and erect the building. Once the building is up, square and plumb, you can dump a bucket of water around each pole to settle the soil one last time. That's it! The posts working together will stand for a long, long time.

My best,

James

 

[Edko]

Re: Dry vs. Wet Pour Concrete For Pole Barn

I'm with you.
I prefer concrete and wet concrete at that. This would be the strongest way to go. I think our freeze line here in MD is like 32"-36".

Central MD is 36"

 

[Mike Robinson]

Re: Dry vs. Wet Pour Concrete For Pole Barn

I'm no contractor nor do I have any expertise in pole barns. (never even heard of them before). But, if I was a contractor and I had a prospective customer who wanted a wet pour I would do it, as long as I felt there was no harm in doing so. I would just be up front about the fact I don't feel it's necessary and charge accordingly for the extra expenses incurred.

Seems like this what getinmerry asked for so why the resistance on the contractors part?

 

[sschefer]

Re: Dry vs. Wet Pour Concrete For Pole Barn

I'm no contractor nor do I have any expertise in pole barns. (never even heard of them before). But, if I was a contractor and I had a prospective customer who wanted a wet pour I would do it, as long as I felt there was no harm in doing so. I would just be up front about the fact I don't feel it's necessary and charge accordingly for the extra expenses incurred.

Seems like this what getinmerry asked for so why the resistance on the contractors part?

Exactly, talk about beating a dead horse. Just get a permit and have it built to code.

 

[CLydesdale1957]

Re: Dry vs. Wet Pour Concrete For Pole Barn

Wet pour is the solution.

Embedded posts must resist numerous forces - uplift, overturning, settlement and frost heave.

I was on the ASAE Structures committee which wrote most of the standards for column embedment. There is only one version which is adequate to prevent columns from pulling out of the ground - concrete encasement. Actual university studies verify this. As pole buildings are very light, per square foot of area enclosed, the weight of the concrete adhered to the columns is needed to resist the uplift forces.

As to settling, the weight of the building itself PLUS the weight of a failure snow load must be resisted. Rarely is the building small enough in span, columns close enough together and snow laod light enough so a concrete "cookie" or punch pad would be adequate to resist the downward load. Encasement in concrete allows for the loads to be spread not only downwards, but also to the soils surrounding the encasement.

Frost heave - pretty simple, extend the hole depth below the frost line, make the bottom of the hole wider than the top (a reverse cone) and backfill with concrete.

The only way to get an adequate volume of concrete is wet pour. Consider a hole even as small as 24" diameter, 40" deep filled the bottom 60% with concrete as a collar takes approximately 1/4 yard of premix. A yard of premix weighs 4000#, so it would take over 60 60# bags of premix to be an equivalent.

Why do builders use the "dry mix" method, they think it is quick and easy - neglecting how much easier it is to work on posts which are encased in concrete. As soon as the concrete sets, you can remove braces and build. The posts do not move and braces are not in the way of moving materials, ladders, etc.

After being involved personally in over 13,000 post frame buildings. It is the only answer.

Best regards ~ Mike

 

[jakebrake]

Re: Dry vs. Wet Pour Concrete For Pole Barn

im not a fan of dry batch. it has a tendency to head pack. also, there is little to no control over water cement ratio.

3500 psi non air entrained concrete. pour at a 3 inch slump and vibrate it in place to ensure compaction.

concrete requires a minimum of 70 revolutions of the barrel to ensure proper homogenization....period.

 

[v1_0]

Re: Dry vs. Wet Pour Concrete For Pole Barn

concrete requires a minimum of 70 revolutions of the barrel to ensure proper homogenization....period.

Arrgghhh!! You sir, are cutting corners. It is mathematically proven that it requires exactly 71.25 revolutions.

As you well know, one revolution is exactly 360 degrees. It is well known that concrete setting time goes up aproximately 33% for every 10 degree decrease. By cutting the corner and reducing the 1.25 revolutions, you are leaving off 450 degrees, which increases the setting time of the concrete by 1485%. So, if the concrete should normally set in 8 hours - you have increased this to 118.8 hours!

This is nefarious! A home owner would expect the pole to be set within the 8 hours, and would start to use the structure - little knowing that the concrete still requires an additional 5 days to reach it's strength!! Disaster!!!

It's this sort of corner cutting that causes structures to fail, people to get hurt, and global warming to occur.

 

[pinecrestwoods]

Re: Dry vs. Wet Pour Concrete For Pole Barn

After being involved personally in over 13,000 post frame buildings. It is the only answer.

Best regards ~ Mike

Mike- did you really mean 13,000 buildings? That's 1 every single day for nearly 36 years. If that's true, you're certainly not the guy in the trenches. There would be no time to get dirty! You must be the guy driving by in the pickup.

To OP- just do what makes you happy and gives you the most faith in your building. ALL building methods you've come across will out last the materials used. The finish will be gone from the metal, boards will be rotting, etc. before you will notice a problem with it pulling out of the ground or levitating. If your building experiences enough force to pull it out of the earth, it's probably for the best that it is GONE, because it would need such extensive repair, it would be a 100% loss.

As for wet pour.... that's an age-old argument that most deck guys have.... drainage vs. holding moisture against your wood (so to speak).

The BIGGEST considerations in the strength and longevity of your building will be the skills of the crew building it and the materials used. You've done your homework. Go for the one with the best CRAFTSMANSHIP, and don't worry so much about wet pour v. dry.

As a side note, the dry is actually easier to make sure your building is perfect. You can make those fine adjustments to plumb and true everything..... adjustments that you won't know need made simply by holding a level at the bottom of a (probably) really tall post.

 

[The_Kid]

Re: Dry vs. Wet Pour Concrete For Pole Barn

I was on the ASAE Structures committee which wrote most of the standards for column embedment. There is only one version which is adequate to prevent columns from pulling out of the ground - concrete encasement. Actual university studies verify this. As pole buildings are very light, per square foot of area enclosed, the weight of the concrete adhered to the columns is needed to resist the uplift forces.

If that is the case why does the ANSI/ASAE EP486.1 Shallow Post Foundation Design section 4.3 list granular aggregate, and excavated soil as being acceptable back fills? Page 2 of pdf.

http://www.nfba.org/files/documentlibrary/TechResources/EP486.1 _Shallow_Post_Foundation_Design.pdf

The only way to get an adequate volume of concrete is wet pour. Consider a hole even as small as 24" diameter, 40" deep filled the bottom 60% with concrete as a collar takes approximately 1/4 yard of premix. A yard of premix weighs 4000#, so it would take over 60 60# bags of premix to be an equivalent.

Volume is volume. A 1/4 yard whether it is premix or dry is a 1/4 yard.

Why do builders use the "dry mix" method, they think it is quick and easy - neglecting how much easier it is to work on posts which are encased in concrete. As soon as the concrete sets, you can remove braces and build. The posts do not move and braces are not in the way of moving materials, ladders, etc.

If I set a post in premix I have to wait before removing any braces because the premix is still fluid until it sets. If I set a post using tamped crushed rock, earth, or dry mix, I can remove the braces as soon as the hole has been filed.