footing for pole barn posts

[mopower440]

I got the 'how to build a pole building' book by Mthew Logan, he says for the pole footings to either pour concrete in the holes or pour a 45 pound bag of gravel in the holes for the post footing, i figure the gravel would be easier than fooling with cement, but where do you buy bags of gravel?

 

[cowboydoc]

You can buy bags of gravel at any home supply store like Menards, Lowe's, Home Depot. The cheapest way would be to go to your local quarry and get a pickup load of it. The easiest way is just to get some oval concrete footings. They are usually 12-14" in diameter and 4" thick. You just drop them in the bottom of the hole and put your post on top of them. No fuss and no mess.

 

[CTyler]

Thats what a lot of pole building companies do. Drop a round, octagon, etc.. patio block down the hole.

 

[Molerj]

Or you can buy the bags of sakrete & just empty the bag in the hole, dry.

 

[yellowdog99502]

Be sure to check with your local building department. Some get rather tough on footings for post type construction. Depending on your soil conditions, gravel may not be the best choice.

In a worst case situation, a 30' wide building with posts at 8' on center and a 30# snow load gives a load of 3600 lbs at the footing (no dead load included). For a 4 x 6 post the equals 150 psi or 21,600 psf. Not very many soils will support that load. By using a 16" diameter footing that load is reduced to 2,580 psf. The footing depth (thickness) must be 1/2 the diameter of the pad.

There are several companies that supply the pole barn industry throughout the country and carry a precast 'cookie' just for this use.

Secondly, if you go with the dry pre-mix, be sure to add water and mix it in the hole and let it set before placing the posts. We have seen several structural failures caused by simply pouring the dry mix in the hole and expecting the available ground water to permeate into the mix. It just doesn't happen all that easily. I know there are a ton of buildings that have been done this way with no problem, but, I have never felt that lucky.

Concrete is cheap insurance compared to a building that decides to sink.

Enjoy the project,

Don

 

[mopower440]

I like the idea of patio blocks, but wouldnt i need to double stack them to make them strong enough?
also, i like the idea of pouring the dry premix into the hole and adding water, then mixing and letting it harden, but wouldnt i still have to mix sand in with it to make it right?

 

[gerard]

My contractor used solid 3 x 6x16 blocks, put them in the bottom of the hole, dump in a bag of sakrete dry which fills in around the block (he used an 18 or 20 inch auger so the holes were pretty big), place the 6x6 post and dump in another bag of sakrete dry, then backfill the entire hole with running crush and tamp. No need to water, the concrete will absorb moisture from the soil and cure just fine. (Remember with concrete the less water in the mix the stronger the concrete, just may take a little longer to set up if you dump it in dry.) Using two blocks wouldn't hurt but the blocks are pretty strong in compressive strength as long as they sit on a solid base. All the block is doing is spreading the weight of the post over a bigger footprint so you'll get less settling. Anything that accomplishes that same goal will work just as well. (You can use big flat rocks if you have some handy)

 

[jmc]

Yellowdog,

I felt the way you do about leaving dry sakcrete hydration to chance but I just had Morton put up a barn for me and they put it in dry. When I asked them about it you could tell that a lot of their other customers had probably questioned them on it and I think they would have mixed it if I had pressed them. In the end, I relied on their reputation and experience of 100 years in this business.

This is my second Morton building and they don't skimp on anything- material quality, structural, or skilled labor. I'm kind of picky about construction details and watched their progress closely. When they were done with it I couldn't help but congratulate each one for doing such a careful job. Anyway, it could be that they knew that this southern Indiana clay would provide the water the sakcrete needed and they may not leave it to chance in other types of soil.

As an aside, their opinion on concrete "cookies" was that the bottom of the holes are not clean and flat. The cookie may rest on the temporary high points of the bottom and settle later.


John

 

[mopower440]

what about this guys, i ahve used this premix from lowes before, you dont need to add sand to it, just water, i did it for my mailbox post, directions said to pour the dry mix into the hole, then add 1 gallon of water and stir it and let it set, no sand mixing involved, would this be sturdy enough? i could just dump the bag in the hole, add the water, mix it up and let it harden, instant footing, then i can set the poles on top of it..?

 

[Molerj]

Just to add my .02 worth. If you are going to add water to it, it would be easier to mix it in a wheelbarrow than trying to mix it in the hole. Then when you dump it in the hole, you would be sure that it would level out because it would be thoroughly mixed up.