Pole Barn Post Footing

[Bill VA]

For pole barns - where the wood post (6x6) is buried in a post hole, what are you doing for a footing under the post? Concrete,
gravel, nothing - what is your footing?

I've thought about putting down a thick gravel footing - tamped, setting the post and filling the hole with more gravel and whatever
dirt came out of the hole.

I'm leery of concrete around the poles and even under them thinking they will trap water under/around the pole.

Not using any kind of perma-columns, this barn is low budget pole barn for some hay and equipment storage.

Gravel makes me think a couple of things - ballast under the pole to keep it from sinking and drainage.

What kind of footer do you use on your pole barn poles?

Thoughts?

Thanks!

 

[caterpillar guy]

We set them just like a fence post. Put the old dirt right back in the hole. Keep the dirt heaped around the pole till it settles so the water doesn't set to rot the pole out just like a fence post. tamp with your shovel handle as you put the dirt back in or with a stick about that same size to get pole solid.

 

[Bob Bancroft]

Here in NY they have quit putting concrete around the poles. They place pre cast concrete discs in the bottom of the hole. Over the past few years, I have paid for quite a few post holes. Fortunately no one has tried to sell me any!

 

[Walston]

I think it depends on where your are and the soil bearing capability. In Ohio we just set them on the ground below the frost line and fill in the hole with the dirt we dug out. Never had an issue.

 

[john in la]

Anyone that puts up a pole barn without concrete footing to spread the weight over a bigger area is asking for trouble.

Lets look at what you are asking.
Most soil has a bearing capacity of 2000 to 3000 lbs per sq ft.
While most use 2000 lbs when no soil test was done to be conservative lets use 3000 to play into the hand of the no footing crowd.
So how wide is your building? 30 ft
Wall height? 10 ft
Truss spacing? 8 ft

So you have two 6x6 post carrying 8 foot by 50 foot of wall and roof.
Two 6x6 post has a area of .5 sq ft
.5 sq ft x 3000 lbs of capacity gives you 1500 lbs of capacity
Do you really think 8 ft by 50 ft of building weighs less than 1500 lbs

If you are really worried about the post sitting on a concrete footing put a layer of gravel between the concrete and the post.

Another thing most do not worry about is uplift.
While uplift is not constant like down pressure is uplift comes in greater forces.
You might want to add uplift protection to the post also.

Now I can sit back and read the responses from those that will say I have a 2000 yr old pole barn with no footing and 2x4 post and it hasn't sunk 1 inch.

 

[Texasmark1]

Well presented John.

My first building, a self built 40x40' corrugated tin, 5' diameter on 8' center, 3' post in the ground with nothing but dirt, built in 1978, has sunk at least a foot, some parts of it more. I have sliding doors on the front and have taken them off twice to cut the bottoms off so that they will still slide. I'm in Houston Black Clay and it is described by one local Civil Engineer (that did our community water well design) "unfit for dwellings and roadways".

Since I am going to die in this place one day, I am pondering just what I am going to do about all my buildings sinking....getting a back ache and knots on my head from having to duck every time I enter one of them.....house is sinking too....and one 24x30' addition just moved away from the main house 6" over several years (had a house moving crew put it back this year), yard full of sink holes, concrete set fence posts working their way out of the ground, roads are a constant problem for construction crews as they keep sinking here and upheaving there.

 

[FBH44]

Sounds like you want it to last? Make sure your poles have enough chemical pressured in to make it a permanent pole foundation. Ordinary treated lumber does NOT have enough chemical. I've had treated poles get eaten up by termites in 15 years.
?NatureWood? Alkaline Copper Quaternary ACQ Minimum 0.60 pcf ACQ
for Structural / Building Pole / Foundation Use

?Micro-Pro / Smart-Sense? Micronized Copper Quaternary MCQ Minimum 0.60 pcf MCQ for Structural / Building Pole / Foundation Use

?Micro-Pro / Life-Wood? Micronized Copper (tebuconazole) Azole MCA Minimum 0.23 pcf MCA for Structural / Building Pole / Foundation Use

Ordinary lumber yard poles might not have enough chemicals.
Those poles might only be approved by the manufacturers for decks or fence posts, NOT for permanent structural building foundations.

 

[showcrop]

A pole barn is a low cost structure framed up on poles set into the ground below frost level and on virgin native sub soil. For the building to last the subsoil needs to be reasonably well drained, and well above the water table. The poles won't be stable if the ground is wet. When you get into footings and foundations you are into much higher cost structure. It all depends on what your needs are.

 

[Ray IN]

I do not think rock for drainage will do much good, as it seems that the soil will pretty much be moist all around the posts at all times with or without rock. It may help some with weight bearing, but a concrete "cookie" about a 12--15 inches in diameter is what they recommend in Indiana under all posts where the building is wide. For a small building less than 32 feet wide, it probably will not need anything but half a bag of concrete mix in the bottom under the post.

 

[john in la]

Post for my new building.
This should last at least a couple of years.

 

[paul]

Typically you need a little bit bigger pad under the pole to keep it from pushing down, and it?s best to have something to keep the poles from pulling out of the ground in high winds, so folk mostly use some concrete in the bottom of the hole.

You didn?t say what size building, small might not make much difference, a typical nice farm shed these days you need some weight bearing umder those poles.

Paul

 

[MarkB_MI]

Our township building department is very specific about how posts should be set. The post must sit on a concrete plug ten inches in diameter and ten inches thick. The top of the plug must be at least 42 inches below the surface so it's below the frost line. The first foot of back fill must be pea gravel.

The plans for my building specified larger plugs for the footings, 12 inches in diameter and 12 inches thick, so that's what I did. Obviously bigger is better; you don't want your building to sink under its own weight.

After putting in the 12 inches of pea gravel back fill, I dumped in half a bag of dry Quickcrete. I did that because it really locks the post in place. Since it's above the pea gravel it shouldn't affect drainage. The rest of the fill is dirt.

Some folks recommend putting an asphalt shingle between the plug and post; the weight of the building will smash the post end into the shingle and seal off the end grain. I guess it can't hurt.

 

[RedGreenGuy]

Mine has 12" x 6" 6 sided concrete plugs at base of each post and holes are filled with rock not dirt

 

[jon f mn]

Around here the important part is getting below the frost, at least 4'. Some use the concrete pad, but most just sit in undesterbed ground. Nothing sinks here, but frost has pushed a few your of the ground.

 

[rustyfarmall]

I had a pole building erected just 2 years ago. 1 sack of quick-crete per hole and then dirt.

 

[jm.]

You got it , over 6 buildings each of which are over 40 years old here in Tennessee and I do not think any of them have ever moved up or down in the years. Around here normal is dig a 12 inch hole about 40 inches deep dump half bag of quick mix in the hole and tamp it down good then place the pole and fill with dry quick mix.

 

[Andy Martin]

(quoted from post at 03:10:16 04/14/19) Anyone that puts up a pole barn without concrete footing to spread the weight over a bigger area is asking for trouble.

Lets look at what you are asking.
Most soil has a bearing capacity of 2000 to 3000 lbs per sq ft.
While most use 2000 lbs when no soil test was done to be conservative lets use 3000 to play into the hand of the no footing crowd.
So how wide is your building? 30 ft
Wall height? 10 ft
Truss spacing? 8 ft

So you have two 6x6 post carrying 8 foot by 50 foot of wall and roof.
Two 6x6 post has a area of .5 sq ft
.5 sq ft x 3000 lbs of capacity gives you 1500 lbs of capacity
Do you really think 8 ft by 50 ft of building weighs less than 1500 lbs

If you are really worried about the post sitting on a concrete footing put a layer of gravel between the concrete and the post.

Another thing most do not worry about is uplift.
While uplift is not constant like down pressure is uplift comes in greater forces.
You might want to add uplift protection to the post also.

Now I can sit back and read the responses from those that will say I have a 2000 yr old pole barn with no footing and 2x4 post and it hasn't sunk 1 inch.

Nice analysis but you missed the shear strength of soil on the side of the post.

As someone else said the key is local conditions. Bill needs to find out what works in his area. I like the idea of gravel below the post unless the water table in the area is that high. Most places it is not. Gravel provides a cheap spread footing.

My pole barn with no footings is over 40 years old now and not sinking. But that's my local conditions. My pole barn that is 35 years old with concrete around the poles has a couple of poles which are showing significant failure.

In Virginia Bill does not have to worry about frost heave, and with his talk of hills, no worry on high water table either. Maybe.

 

[Pops1532]

Check your local building code.
Here we have to use a 10" thick concrete cookie or pour 10" of concrete in the hole.....for the very reasons John mentioned.

 

[FinnMD]

Pole barns I have, auger at least 4 feet and set a concrete pad at bottom about 1 ft thick and let cure. Poles should be treated rated for ground contact. I drilled through bottom of 6x6 pole and hammered a piece of rebar sideways to stabilize pole and help prevent uplift. After set on concrete pad I dumped one more bag of concrete with gravel and then fill with soil.

 

[JD Seller]

I would put concrete in the bottom of the hole to support the load. Just dumping some sackcrete in may work in some places but not in my area that we get deep frost. The frost will move the post up and down. I have one shed that is raising out of the ground. I have had two different shed additions that where added to the sides of existing barns that sunk over the years. In the last ten years, we have jacked them up and put concrete columns under them. We go six foot deep to make sure and get below the most common frost line.

As for trapping water with just a plug poured and the post setting on it. I do not think that there would be much water held just by the post setting on top of a poured concrete plug.

Also spend the money to get the properly treated posts. The cheap ones at the box stores do not have enough treatment to last very long in direct ground contact. Also watch the post that many of the Amish sell in barn "kits" they many times are based only on price, so you get cheaply treated post.

Think of this. Pouring concrete plugs under the posts might cost you $100-200. Now spread this over the usable life of the barn. Then think about the time/trouble you could easily have IF your post sink. Too many time when we cut corners we shoot yourselves in the foot for little gain.

 

[Jeff NWOH]

My 40 x 80 sits on concrete plugs 18" in diameter and 12" thick. That's what the building inspector told me to do.

 

[Northvale PA]

The point load on a 6?x6? post needs to be carried by the bigger footing. A heavy snow load will double the the weight of the building load. Unless you are on solid rock, plain soil will settle under the load. Footings spread that load out.

 

[Dave H (MI)]

They sell post hole sized concrete plugs for setting poles on now. My building was big enough that I had to have the local barn builders come in and put it up. That is what they used and it seems to work good. They drill the hole and place the plug in the bottom.

 

[MarkB_MI]

Some quick math:

A 6x6 post (5-1/2 x 5-1/2) has a cross-sectional area of 30 square inches.

A 12 inch diameter round plug has a cross-sectional area of 113 square inches.

 

[caterpillar guy]

I guess I should have said the poles are about 4 ft deep. All have been here for over 40 years. Last one was built in the early 80's late 70's. It even has overhead space for hay storage. Though that is set on separate posts and timbers. Still though the poles were set about 3 feet and another 2 feet of fill was added around the poles for floor work as a freestall barn for the cows. Have not had problems with being pulled out of the by wind or tornadoes. As for settling never noticed it. I don't go around and measure the poles to see. I can still put the same height equipment in them we put in 30-40 years ago.
I suppose if I was going to put an overhead crane or jib crane or such I would probably look into something more as I would be expecting the building to hold specific weight additional to the building.

 

[Eldon (WA)]

Code here requires a minimum 2' diameter hole 4' deep with 6" of tamped gravel then filled with concrete. Expensive, but nothing is going anywhere. Some builders are starting to use steel brackets set in the concrete with wood laminate above grade.

 

[john in la]

And take that one more step.

3000 lb soil equals 20.83 lbs per sq inch.
So your post will hold 625 lbs
And the concrete plug will hold 2354 lbs

On 2000 lb soil it would be 416 lbs and 1569 lbs.

And yes you do get a added benefit from the friction of the side of the post against the soil so the deeper you go the better off you are.

 

[Goneranchin]

Man that will preach! I always ask myself what would I pay then to avoid the problem that I have now.

 

[dpendzic]

the 6 x6 post can easily withstand 500 psi compression parallel to grain, so it can hold 500 x 30 =15000 lb load

 

[Leroy]

Few years ago neighbor had a new pole barn put up. About 2 years later wind and it pulled every post out of ground and destroyed barn. Insurance rebuilt it.

 

[Dick L]

Here I go 4 foot for the holes and dump a half bag of sack crete in the hole. It will harden on its own. The dirt coming out of the hole is tamped in after the pole is lined and plumb. Floor poured to top of bottom penna. No code here. We are in heavy clay. The auger smokes in late summer boring the holes.

 

[john in la]

Yes the post can handle 15,000 lbs.
What we were talking about is most soil can only hold 2000 to 3000 lbs per sq ft.
So this makes the post sink into the ground without a footer.

 

[dpendzic]

yes definetly--the funny thing about soil pressures is that its allowable value does increase substantially as you go deeper into a soil--too lazy to find and dig out my soil mechanics books but i was impressed when i did bridge footing designs--here on Long Island,being basically a sandbar, we used 5000 psf as a start, but have recorded in tests up to 15000 psf with acceptable settlement

 

[Stephen Newell]

If you are talking about 6x6 pressure treated I just drop them in the hole, and back fill with concrete. They are rated at 30 years duty life and I've got many about that old which are still in great shape.

 

[Adirondack case guy]

You can glean all the opinions here, but they all go out the window if your local code enforcement officer says something else. Ask them and Do what they say and better it if you wish.
Loren

 

[Steamboat]

I am a firm believer on concrete piers attached to posts. My cedar posts for my porch rotted after about 25 years, jacked up porch an placed piers under them. Trouble was there was standing water and most any wood will rot after years.

 

[MarkB_MI]

> On 2000 lb soil it would be 416 lbs and 1569 lbs.

Those numbers really bring it home. Up north, it wouldn't take much of a snowfall to exceed 400 pounds per post. Here in Michigan, roofs are designed for a snow load between 30 and 70 pounds per square foot. Using 30 psf for an example, a 30 foot wide building with posts 8 foot on center would have a snow load of 3600 pounds per post! And that doesn't include the weight of the building itself.

 

[Bill VA]

Thanks everyone - much appreciated.

I have another barn question, but will ask on a separate thread.

Thanks again!
Bill

 

[Mike M]

Many in Ohio seem to put a concrete "cookie" in the bottom of the hole. Our Lester went a set farther to prevent up lift. It had rebar in a U shape. You put it in the bottom of the hole first,then the cookie,then the post. These rebars stick up above grade. They have an L on the top of the bars. You drive this into the post and then some fence staples help to hold it into the post.

 

[Alvin 41]

Around here (S WI) widespread building of pole livestock ,storage ,and machine barns started in the 60's using round poles set on 12" round 6" thick pads about 4' deep and using 8' or 10' rafter spacing. the poles with creosote base treatment lasted pretty good. By 1970 most were using 6''x6" penta treated poles and they rotted off at ground or concrete level in 20-30 years . I've repaired several by cutting the pole off 6" to12" above grade and pulling the lower 4' out (only the 12'' or so at grade will be rotten) and then bolting a 3"x 4' galvanized angle piece to the pole and filling the hole with concrete up to the cut off . New pole construction now seems to be using laminated 2"x6" based poles with very high rated treatment lumber in ground and on 8' spacing.