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Badfish740 11-10-2008 02:54 PM

Pole barn footing question
I am building a 12x16 pole barn (more of a "pole shed" really) because I just need a simple structure to house my two tractors and miscellaneous yard tools. The poles will be 4x4x12 posts (8 altogether) each buried 48". Frost depth in my area is 42". Each pole footing will consist of a 12" diameter by 48" deep hole. Is it necessary to fill the entire hole with concrete or can I fill each hole to 24" and fill the remaining 24" with earth? I ask because this will of course halve the amount of concrete I need, reducing the concrete cost from $200 (40 80lb bags) to about $100 (20 80lb bags) as well as reducing the amount of time I spend mixing :thumbsup:

concretemasonry 11-10-2008 03:02 PM

Personally, I would not skimp on the footings.

When it comes to horizontal loads on a building, the top half of a 12" post encasement/footing that is near the top is most important. The depth is for frost heaving protection. Using what is available and free doesn't do much good.

Using sonotubes as form and filling around with gravel is ideal. Any dug hole has irregular edges that the frost can grab and heave as it freezes from the top down. Sonotubes will not be pulled out as easily.


Badfish740 11-10-2008 03:31 PM

So in other words I should be digging about a 20" diameter hole, centering a 12" diameter sono-tube in it, filling the area between the sono-tube and hole with gravel, and then filling the entire sono-tube with concrete? Does that sound right?

RippySkippy 11-10-2008 03:39 PM


Originally Posted by Badfish740 (Post 182871)
... The poles will be 4x4x12 posts (8 altogether) each buried 48". Frost depth in my area is 42"....

Are you saying that you're going to set the post in the hole the concrete the post in around 24" deep?

I wouldn't put any pressure treated post in're asking for all sorts of nastys with that set up. IF you using PT post, back fill with crushed stone.

Years and years ago, I helped dad build a pole shed, 60'x100' 6"x6"x16' posts. On his we dug the holes below frost depth, and 4" thick concrete disks we placed in each hole for the post to set on. On the side of each post we added a PT 2"x6"x12" block with I think tempered steel ring shank nails....I think (at the time it was what was being sold a "almost rust proof" Of course the PT then wasn't nearly as corrosive as it is today, so I don't know about all the specifics of the materials. That shed hasn't moved a bit in 30 years.

I like what concretemasonry says...use sonotubes, and I'd add a strongtie connector to fasten the post to the concrete pier. You could use the sonotube with base that would get you up to ground level.

Badfish740 11-10-2008 03:58 PM

Ok, sorry-now I'm confused. In response to RippySkippy, here was what I was given as sort of a "rule of thumb" for pole barn building: I was told that poles (posts) must be set in the ground at least half the length that they will be above ground so 8' above ground = 4' below ground. I was under the impression that one was supposed to set the posts in concrete. I would have gone a similar route to what you described in that I would drop the concrete slugs into the bottom of the hole, set the post in, and pour in concrete around it. Are you saying that's not a good idea? Not knocking your idea, I just don't completely understand.

RippySkippy 11-12-2008 08:14 AM


Originally Posted by Badfish740 (Post 182916)
... a "rule of thumb" for pole barn building: I was told that poles (posts) must be set in the ground at least half the length that they will be above ground so 8' above ground = 4' below ground.

Be careful when given "rules" there's correct and incorrect practices. Think about it...if the side walls were 16', there's no way we would of had 8' in the ground. With out knowing your soil type, I'm guessing you'll be fine with 4' in.


Originally Posted by Badfish740 (Post 182916)
I was under the impression that one was supposed to set the posts in concrete.... Are you saying that's not a good idea?

You got's not a good idea to encase wood with concrete. The concrete holds moisture around the wood. If you're going to sink the post in the ground, you'd be better off back filling the hole with 3/4" crushed stone with out fines. It will give moisture a place to go. Well set posts will have no problem holding your barn.

Do you have to meet any kind of building code? Even if you don't a quick call to a building official in your area may help understand whats required locally.

Here's information from another post in DIY land from 2007 with info being passed on from AtlanticWBConst. Following some of the links say yes, others no. Personally I don't.

Read up on the opinions:

"Pressure-treated pine posts are ideal for fencing because they resist rotting. These posts can be set in concrete to ensure their stability. Many companies offer an extended warranty on their pressure-treated posts to guarantee their quality." - http://www.americanfenceassociation....ood/index.aspx

"Should all posts be set in concrete?
We recommend that all posts be set in concrete in accordance with local conditions and standard building practices. Posts that are not set in concrete will eventually lean due to wind and weather. Check your local building codes through your city or county government for further details." -

"The post can be placed atop a concrete pier, bolted to a steel anchor, or it can be set in the concrete. Placing the post into the concrete pier adds strength, but it is more susceptible to rot." -

"Posts that weren't properly treated or set in concrete typically rot away at ground level." -

"Why are we so concerned about longevity of this treated lumber post? Because treated lumber does not last forever. I have seen treated lumber begin to decay after less than 20 years of exposure to the elements. Anything that can be done to reduce the amount of water next to the post will surely reduce the chances of the preservative being washed away." -

"Question: Is it ok to put a deck post into concrete instead of using an anchor, and if so,will the post not last as long as using an anchor.frost level is 36", how much of the post should be buried in the concrete.will this way be stronger(less sway) than using an anchor. thanks
Answer: Hi Ray. Definitely better to put it in concrete. Should give you minimal sway depending on how high the post is above the ground or deck. I am not too sure about frost levels as my life in the U.S. has been spent in California, Florida and south east Georgia. 24" depth into the ground should be quite O.K. Hope this helps." -

polehouse 05-04-2009 04:25 PM


I am looking to make a large wooden deck area for an open air restaurant. The platform size will be 30' x 30'. There will be no walls. Just the roof structure and support.

The land is sloped. We would like the whole deck to be off ground.

1' elevation at rear ... 7' at front. This is sloping towards the view of course. There is no frost here. Hurricanes are a problem here.

We would like the roof height to be 14' from deck middle down to 7' at edge.

How deep do the footings need to go down? Add that to the highest pole 21' (14' plus 7' deck height from ground) in total = ?

Or can we use a fixture to hold the roof up without a pole all the way up (21')?

Does the fact that many people will be seated add to the depth of footings?

What diameter of pole is needed? Thanks for any input.

Aggie67 05-04-2009 05:42 PM

Hi, and welcome.

It might be better if you start a new thread.

Also, in my neck of the woods, something like this (commercial use) would require a set of drawings from an architect or engineer in order to get the permit. The owner isn't allowed to DIY a design on commercial property.

I think your best bet is to go through the proper process. We here on the boards have no idea where you are, what the wind and rain loads are, what the soil bearing capacity is under the structure, the live loads (although the code treats it) involved, any local regs. When you go for a permit, all of that will have to be designed out in the sealed drawings. The proper process is to call the building and zoning departments to see if they will even allow it, then submit a zoning permit (which will require a site plan and some concept drawings), get zoning approval, then call a couple architects or engineers, pick one, get a design drawn up, and submit for permits. The preferred route is to have one firm do the site plan, concepts, and permit drawings, so you don't pay for duplicate effort.

polehouse 05-05-2009 05:36 AM

OK, I understand.

I assure you that the plans will be drawn up. I was just seeing if the whole thing was viable before spending money on it.

Thanks for your help.

12penny 05-05-2009 07:35 AM

Badfish....I spent a couple years working for a company that only did pole buildings. For a 6x6 pole you'll be fine with a 12"dia hole. Clean out the bottom of the hole so theres no loose soil and then tamp it solid. You can either put a prefab concrete disk in the bottom or pour 4-5" of concrete. When you set your post simply drop it in the hole, plumb and backfill with soil, tamping every foot or so. Make sure you use posts rated for ground contact as not all PT lumber is. We left our posts long and then trimmed the tops with a chain saw to the proper elevation.

BillyWillBill 05-29-2009 09:57 PM

12 Penny...finally an accurate answer...thanks!!!!:thumbsup:

DigitalDreams 05-31-2009 06:06 PM

Listen to 12 Penny
I have put up a number of pole sheds over the last 30 years most are still standing solidly with a 4 to 6 inch 12 inch disk in bottom of frost depth hole
and back filled with sand or construction gravel the posts if treated have not rotted off and the only thing that may vary is if you have certain types of soil
you may need a bigger diameter disk and thicker if larger building with more load.
I have 2 pole barns built to commercial code here in the state I live and on very unstable peet moss soil and the only thing that had to be changed is instead of 4 inch thick 12 inch disks 4 foot deep frost holes I had to use
1 foot thick- 24 inch disks in 4 foot holes and both of those buildings meet code in one of the toughest states for codes next to california.And these are buildings 40 x 100 foot not a little 12 x12 pole shed.

markcrain 08-21-2011 09:06 AM

Has anyone ever considered using a paint on bed liner to protect the post underground?

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