Should I Be Afraid of a Pole Barn

[Gizmo2]

If the post is not setting on top of a pad of concrete, the area that is supporting the weight of the building has been reduced to the cross sectional area of the post, which is pretty small. The weight of the building will force the post through the concrete collar, so I don't see what the value of the concrete is. Normally a building will require about a 16" diameter concrete pad to achieve sufficient area for soil loading.

IMO, So water can get trapped and rot the pole.

 

[Nissan197]

I have a pole barn and also live in KS. My posts are treated and were placed in a hole with gravel and concrete. It has been through many wind storms and has held up.

 

[Depmandog]

If the post is not setting on top of a pad of concrete, the area that is supporting the weight of the building has been reduced to the cross sectional area of the post, which is pretty small. The weight of the building will force the post through the concrete collar, so I don't see what the value of the concrete is. Normally a building will require about a 16" diameter concrete pad to achieve sufficient area for soil loading.

The bottom of the holes were virgin undisturbed soil. Gravel was placed in the hole (6") to keep water away from the base of the posts. Once the post was placed, it was dropped up and down repeatedly to compact the gravel. So the post was setting on a solid footing.

Have you ever tried to pull out a post (any post) that has been concreted in place? It's almost impossible without digging the dirt from around the concrete. Use whatever you want to pull it. It is held in-place by the bond of the concrete to the post and the resistance of the concrete to the soil. If it is so hard to pull up, likewise it just as hard to push down (even more difficult because it is resting on a compacted base.)

Don't mean to be argumentative, but I have considerable experience building structures. My methods work fine for Missouri soil. If I were building in sandy soil or other I would reconsider my methods.

My building has not (nor will not) settle. It has been 10 years.

Have a great day!

Dean

 

[BeezFun]

The bottom of the holes were virgin undisturbed soil. Gravel was placed in the hole (6") to keep water away from the base of the posts. Once the post was placed, it was dropped up and down repeatedly to compact the gravel. So the post was setting on a solid footing.

Clay soil can support about 2000psf, pure gravel is around 5000psf. So unless the concrete collar was engineered to become an integral part of the post, ignore it and figure out how much load the post can support directly on the gravel. Either the gravel or the soil will shear first, need to figure out which. If it's 6x6, each post is 1/4 square foot. The gravel supports 5000psf so that post will support 1/4x5000= 1250 pounds into the gravel. Loading spreads about 60degrees from horizontal in gravel so if there's 6" of gravel, the load is projected out to the side about:
6*tan30= 3.46 inches. Post is square but assume it's round 6" diameter to make things easier, so the increase in area is about a factor of 10, which means the 1/4 square foot post loading is spread over about 10/4 sf of soil, call it 2.5sf. So that's 1250lb/2.5sf= ~500 psf, which is well below the capacity of most soils. So the limiting loading is into the gravel and you can have about 1250 pounds on each post.

Not sure what a building weighs but it's not that hard to add it all up and divide by the number of posts. If that number is less than 1500 it should be OK, if it's greater, probably not so good.

For comparison, a post sitting on a 16" round concrete pad has area:
3.14x8**2/144 = 1.4sf
If it's on 2000psf soil it can support:
1.4sf*2000psf = 2800 pounds
Which is about two and a half times putting it on gravel. That means you might have to have 2.5 times as many posts in a pole barn set on gravel to support the same weight as if you put it on 16" concrete pads. That assumes it's all well drained, add water and all bets are off.

 

[two_bit_score]

I removed a wooden fence from my former property in Harris County Texas in 2004 that I had owned for more than 20 years and the fence was built in 1970
The boards and runners were somewhat rotten, but the post when pulled from the ground (embeded in concrete) were just like new. Some of the bottoms were bare of concrete for 4" or more with no signs of rot. These were in a poorly draining area and stayed wet during the winter months. I dont think you would have any problem with rot in a properly treated and concreted in post. When placing concrete around post, I like to place a bit of concrete in the hole first then place my post to insure complete encasement, then I mound up the concrete around the top to form a conical shape that drains all the water away from the post. Concrete bonds to the wood well enough to form a water tight barrier. That being said, my preferred method would be to pour a concrete pillar with 4 vertical rebar reinforcement and 6x6 wire mesh cage around the rebar, embed galvanized anchor bolts and then using L shaped brackets, bolt the post to the concrete pile.

Concrete keeps the termites away from the wood.

 

[timswi]

Built a 30x30 6x6 PT pole barn is 1994 and it still looks like the day I built it...Built one at the new house 7 years ago (30x48 6x6 posts), and it still looks like day one..Don't be afraid.

 

[Luremaker]

The State of Colorado wants at minimum a 24" concrete pad. Does not matter what the guys here put under their post. You must follow the local code and put what your local building official wants under the posts.

 

[BeezFun]

The State of Colorado wants at minimum a 24" concrete pad. Does not matter what the guys here put under their post. You must follow the local code and put what your local building official wants under the posts.

Yes, it's good guidance, that's what I would do whether it's code or not. There is nothing more important or difficult to fix later than the foundation of a building.

 

[whistlepig]

A concrete pad under the posts is a given. Without the pads under the posts the poles will sink. That's code around here and truly just plain common sense.

 

[Duffster]

The State of Colorado wants at minimum a 24" concrete pad. Does not matter what the guys here put under their post. You must follow the local code and put what your local building official wants under the posts.

It's pretty ingnorant on their part to say that a 24" cookie is needed.

Big difference between a 24' building on 8 foot center vs. a 80' or more on a 10 or 12 foot center.