Your local county extension office should be able to tell you what
the projected frost line is in your area, or perhaps a local
Frost line here in Alabama is the grass line! My water line from the
main is only 6 to 8 inches deep......
Put some color in your cheeks...garden naked!
"The original frugal ponder"
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This Kentucky source indicates a frost line of 30", but you would still
be best asking the local practices from the local building inspector, as
frost lines can vary. The frost line is more or less arbitary, but is
intended to cover most years. In a really cold year the frost can go
lower and freeze pipes.
I used to live in Kansas. Same latittude, frost line was three feet for
If you think a severe thunderstrom might happen sometime in the life of the
barn, I'd go deeper than that. Poles hold your barn from blowing away.
stryped, this discussion has been going on for weeks, and you've still not
gotten the point --
The barn won't tend to simply shear horizontally in a strong wind. Rather,
it will shear diagonally, torquing all the poles at the point where they
enter the soil. If the poles are sized to take the expected wind-shear,
then the limiting factor determining whether or not they "undig" themselves
from the ground is how deep they are planted.
Do this: Get a strong, sound 2x4, and plant it like a pole two feet deep.
Do another one four inches deep.
Now, hold the top of each pole steady upright while you try to push the
bottom of the pole horizontally. Can't, can you? That's the action you
seem to think the wind will have. No.
Now pull on the top of the pole horizontally. You'll probably break the two
foot deep one; You'll easily tip the 4-incher right out of the soil.
THAT is the action wind will have on your barn.
Concrete collars around the poles will only provide resistance to that kind
of force if they are as deep as recommended for the pole. Collars are more
designed for straight-line lateral forces.
I agree with almost every thing you said except the part about the
collars. In a former life I did the engineering for a factory built
house company. Lots of our sales were for vacation homes built on
piles. The best information on piles or poles I found in a pamphlet
put out by the Outdoor Advertising Association. Billboards get lots of
They recommended concrete collars around the upper third of the pole.
The reason was to increase the effective diameter of the pole. The
soil at the bottom of the pole has a lot of weight above it, and will
resist the pole moving. At the top of the pole the earth does not
resist moving as well. So a concrete collar increases the diameter and
makes the pole more ridgid.
Don't believe me. Bury that two by four end about two feet deep. Now
rock the top back and forth. The bottom of the two by four harly
moves, but the ground around the top does.
Lloyd E. Sp> Concrete collars around the poles will only provide resistance to that kind
I think that 2 feet is not enough. I would go for at least three feet
and depending on how big your barn is I would use bigger poles too. It
is not all that hard to put the poles in the holes. Just dig out to
the side of the hole a shallow trench about six inches deep and maybe
three feet long. Roll the pole so the end in over the hole and the
pole is in line with the trench. Lift on the top end and walk toward
For telephone poles put a two by six in the hole for the end of the
pole to rest against and use a couple of come-a-longs so that the pole
will not pivot sideways.
No, I do believe you. The recent discussion has been more about "pads" as
collars than about going down a substantial distance. You're 100% right.
But, if you will, comment about the value of just a 6"-10" thick pad at the
very top of a pole's earth contact.
Building codes in Lexington require 18" W footers 42" below grade thus a
total of 42" depth by 18" wide. That means that using an 18" wide footer and
the bottom is at 42" from the top of your finished elevation you will meet
the building code. This is determined by the frost line and as previous
people have indicated that is around 30" here in Kentucky. If you are
building a pole barn I'd rent a two man auger, sink my holes 48", stand my
poles plumb and fill with concrete to the top. Obviously you will have
previously determined the wind direction and positioned the barn so that the
least amount of eave under hang is getting the most general amount of wind.
Having built my share of pole sheds in windy N Texas I can tell you that if
you have a roof with an open area that will catch the wind it WILL catch the
wind and become a huge sail. Sinking the poles just in earth is OK but with
the termites here in KY the concrete gives you that much extra protection
from those nasty creatures.
Surprised to see this thread still going. You need a system to resist horizontal
loads. If the poles are not deeply embedded then you will need a system of
diagonal braces in every plane (including the roof plane(s)). Even with diagonal
bracing to resist horizontal loads, you will still need a system to resist
uplift. This will usually be concrete footings for the posts. The amount of
concrete needed depends on the weight of the building and the roof area
supported by each pole. In high wind areas in NZ (55 M/s) the requirement is to
design for a uplift of 100Kg/sqr. metre. If the poles are to resist horizontal
loads without diagonal bracing then they are working as cantilevered piles and
the theoretical resistance to movement at the top of the pole goes up as the
square of the depth of embeddment. Deeper is much better. My guess is that 3 or
4 feet of embedment with a concrete collar around the top third of the pole
would be about right. Don't underestimate wind loadings, wind loading goes up
exponentially with wind speed. One useful trick is to set a small concrete
culvert vrtically in the post hole, pack earth and rubble around this to hold it
in place and then you have room to manuever heavy posts into exact alignment
without crud dropping into the post hole as you do so. When you have the post
properly positioned inside the culvert, wedge it in place and and fill the
culvert with concrete. Hey presto!.
Well it would be better than nothing. 10 inches would be about right
for a pole that was only set in about 2 1/2 feet. If I were only going
to put in six inches of concrete, I would put it in about four to six
inches below the surface.
Depending on what the soil is like, using cement mixed with the soil is
another option. Often a lot easier to do than using concrete in areas
where one can't get a truck close to the site.
Lloyd E. Sp>