Installing post in a pole barn

ch47dpilot · Jan 26, 2011

I'm currently starting the layout for a 24x36x14 pole barn. Here in Alabama the roof trusses are made from steel not wood(Dixieland Metals of Dothan Alabama - Manufacturers of Metal Roofing and Siding). The manufacture includes about 4 bags of ready mix for each pole. From the threads I've read here everyone says that concrete isn't good for back fill and it should be loose material, ie gravel, dirt ect. I have a few questions that someone could maybe answer.

1. Are we talking about treated or untreated post when people say they will rot in a few years if you use concrete in the complete hole? A book i bought says the complete concrete encapsulation is best to maximize side loads but they never talk about it reducing longevity.
2. Everyone seems to think the best way is to first lay about a 6' layer of concrete first before placing post in hole. If you first let the pad cure won't there be issues with the cold connection between pours. I would think water would wick between the 2 separate pours causing faster decay. If so is there anyway to minimize this? I was think of something like pour the pad dry, place pole in hole then wet just before I do the second pour, which would be mixed prior to going into hole.
3 To help protect the pole below grade has anyone heard or seen of using something in addition the the factory pressure treatment. I would think something like a roofing tar, waterproofing paint, or even some of the do-it-yourself bed liner would make an excellent protectant provide it adhers to the wood.

beppington · Jan 26, 2011

Here in FL - For my 28x22 barn, which started life as a pole barn until I closed in the sides with plywood & 2 garage type doors, I set my treated 4x4s in 3' deep holes, then filled the holes with quikrete. It's only been about 10 years, but no problems so far .. and I will say that my insurance co (State Farm) came out to inspect it, we discussed the 4x4's in the concrete like that, & they insured it & still do; Must be OK.

sal64 · Jan 26, 2011

i used 4x6 presher treated posts on my pole barn the post rest on a concrete pad backfilled with dirt.

AlanB · Jan 26, 2011

Even bus drivers are welcome here

What you are bringing up is one of those questions that get debated till the ends of the earth and nobody seems to have any positive answers.

Mine got concrete. My best friends did not. Seen them done both ways, and seen them rot both ways, and still stand both ways.

The layer on the bottom is to keep the post from sitting in water is the general theory, but that depends a lot on your soil and water table. I like at least 6" of rock or a paving stone or such on the bottom when I do them.

I think (believe) all the things mentioned can only help, I did not do anything like that on mine though.

The single biggest thing I would suggest is to make sure you get the right (most) pressure treated stuff.

I probably have the numbers names wrong but the scale will be about right. Most PT you buy will be .4 pt. That is what you will find at Lowes etc. and most lumber yards. The folks doing pole buildings should be able to get you .6. Don't let your kid chew on it, donate it to make a playground, or chip it and turn it into mulch for the wifes flowers, but if you want it to last a while, that is the one you want stuck in the ground.

Good luck, I have a similar style building.

beppington · Jan 26, 2011

Although I think my existing barn described above is fine ... I've considered for my next, upcoming barn, pouring a concrete footer for each post & embedding a galvanized steel post holder/ bracket into the concrete, so the posts never sits in dirt/ mud/ water. I haven't checked to see what the strength of these is; i.e. Would a barn built this way be sufficiently strong?

ch47dpilot · Jan 26, 2011

Alan B: Some people can drive a bus because they don't need to make up for their short comings(sorry Attack guys)

gary_minnesota · Jan 26, 2011

My 40X45 pole shed/barn was installed in 1992. Have not had any problems with the posts moving or heaving.

The installers drilled 48" deep holes, poured a 6" concrete pad and let it cure over night. The next morning, they set the posts and backfilled around them with 3/4"+ gravel (known in some parts of MN as "sewer rock" for reasons unknown). The soil type here is heavy clay. The gravel backfill is to prevent the clay from grabbing the post and heaving it up when the ground freezes over the winter. It also allows for drainage of any water that may collect around the post from rain water run off.

As others have mentioned, the "correct" way will be dependent on your location, soil conditions and freeze/thaw cycles.

buckeyefarmer · Jan 26, 2011

I think the correct way is the way you are most comfortable with. My posts are .6 Pressure treated, with 20" round, 8" thick concrete footers underneath, and then I tamped dirty stone around the posts. Footings under the posts are for bearing load, the size is based on soil types for your area.

BryanM · Jan 26, 2011

Just curious what are they charging for your pole barn kit? I went too their website and the only price I saw was pole barns starting at $1199. Just wondering what came in their kit?

I tried calling but not their or having somekind of problem with their phones!

Degolyerent · Jan 26, 2011

If you are worried about rot get your PT post from a treater. Get the 60 year treated post the same that is used for docks and bulkheads put conc in hole first then set post plumb and encase them in concrete you will not have to worry about water exposure or rot!

firemech · Jan 26, 2011

I have three boat storage buildings, one 60ft X 200ft and two that are 40ft X 100 ft and all are post and beam that are set in the ground with 6ft deep holes (we have heavy frost in Muskoka Ontario) with 3/4" crusted stone beneath and around each post to grade. These buildings are 40yrs old for the 200 ft and 30 and 28 respectively for the 100ft. The greatest requirement is good drainage the treatment of the lumber. The 200ft building (the oldest) utilized used hydro poles that were heavily creosete treated and in good shape when installed and are still as good as when installed. The older 100ft building utilized cedar poles cut an stripped and dried for a year and the 6 ft ends were coated in thick tar to above grade. This building is in a flood plain area that is wet below grade and the posts are still in good shape but have shown some deteriation of late. The newest building used fresh cut poles that were not dipped and even though was installed in soil with good drainage are showing severe rot at grade level. We have drilled holes between each existing pole and installed sono tubes, placed new pressure treated 6 X 6 posted and poured concrete. A note about the recomendation for sono tube with saddles and posts placed above,,,, a neibour buid a 40 X 60 ft building this way. it was knocked over when a truck backed into the eves. If you go this route make certain you install heavy diagonal bracing to combat any shear forces. It cost more to lift the trusses and repair the posts then it cost to initally build the building. Given I'm long winded thats my two dollars worth.
firemech:confused2:

RoMad · Jan 26, 2011

I would think there is a big difference in the best way to set the poles depending on your soil type, drainage, and winter temperatures. Where I live in Florida most of the pole barns I know of have the poles set in concrete, but of course I haven't seen a great number of them. I have a shed that according to tax records was built in 1972. It is made from pressure treated 4x4's set in concrete. We took out part of one wall and had to remove one of the 4x4's. I cut it off just above the concrete and it was still in good enough shape to reuse on some wooden steps for legs.
I also have a barn that looks to be about the same age as the shed. It is also made from PT 4x4s but they were not in concrete. They were just in the ground when I bought the place. I dug around each of them with a shovel about 18", drove a few big spike nails in them about halfway and then filled the holes back in with sakrete. I thought the spikes would give the concrete something to hold to. Because we get some pretty high winds sometimes, I thought the concrete might help hold down the barn.

yanmars · Jan 26, 2011

Cleary put up my pole building. They put a precast concrete pancake in the bottom of the hole. There posts are three 2x6 sandwiched together. They say so more of the preservative gets completely through. They are the higher treatment for continuous ground contact. They fill the hole with the dirt that came out but compact it with a compactor. Even so the dirt still settles some later.
A number of house magazines say the concrete can rot the post at the ground level but I have seen some removed after many years and that was not the case but they were protected by the building. If they were fence posts in the open perhaps that is different.

TRR · Jan 26, 2011

I have pressure treated posts that have been in the ground for 25 years now. I set most of them in concrete. I dig a hole, put the post in, put a little dirt (sand here in Florida) back in about 2 or 3 inches so water does not collect at the end of the post, and fill the rest of the hole with concrete. I pulled one up recently and the part embeded in concrete was in better shape than the rest of the post that was exposed to the weather.

Note, these are the old pressure treatment formula with arsenic in them not the ACQ stuff. I believe the old style is still available from a dock company if needed. If you use ACQ be sure the fasteners are rated for ACQ otherwise you get to do it over again in 1 or 2 years. ACQ fasteners are generally HOT dipped galvinized or stainless steel. It should say ACQ on the package.

ch47dpilot · Jan 26, 2011

BryanM, my quote is for a 24x36x14. It's only the roof no sides included. It includes everything, 4 trusses, 5 2x6x12 fascia, 20 2x6x12 & 2 14' purlins, 8 6x6x18 poles, 32 bags of concrete, 26 14' panels(26 gauge painted), 4 10' ridge caps and finally all the required hardware. Total cost $2329+ tax(tax in area brought total to 2546.24)

rimshot · Jan 26, 2011

I used 6"X6" P.T.posts on top of a precast 8" thick X12" diameter concrete cookie or disk and set the post. Fill the hole and tamp around as I do with the end of an 8' 2 X 4. I dig the hole about 50" deep with my little CK-20 Kioti as close to straight down as I can get the hole. Drills don't work in this coarse gravel around here. I ran short one cookie so used a drywall compound materiel bucket for a form and poured another.

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