Setting posts for Pole Barn - what is best way to keep posts from shifting?

[CountryB]

I'm setting posts for an open bay post barn this weekend. The holes are 18" diameter by 48" deep. Posts are 8" x 8" x 18ft.

Plans call for me to "float the posts" in the holes then fill with concrete.

What is the risk or chance that posts will shift while concrete is being poured in (pouring off the shoot of ready-mix truck)?

I'm doing this on my own and this is my first pole barn, and want to be sure I plumb and brace poles properly before concrete truck arrives.

Plan is to nail a 2x4 across post at ground level to support (floating) post and then run 2x4 bracing (one north-south and one east-west) to plumb posts. Is that enough to keep everything from shifting when the concrete starts flowing?

 

[prichard]

That's exactly how I've seen it done. If concerned add another north-south and east-west brace on opposite sides.

Are you going to be present for the pour? If so you can keep on top of the situation and slow they feed from the truck down if needed.

 

[Oldoak]

Work like that would be best at least with one helper. If I absolutely had to go it alone, I would brace the poles as you are planning but also dump about two bags of quickrete or sakrete concrete mix (dry, right from the bag, no water) into each hole after you have the poles braced. That will keep the bottom of the poles from trying to kick around as the wet mixed concrete was being poured and help your bracing to hold the poles plumb.

The dry mix will eventually absorb enough moisture to harden like regular concrete. Some pole building contractors used this method and just backfilled directly upon the dry mix with the excavated dirt. It is the building frame that is really going to hold the poles in place.

I'm sure you will get other suggestions, there are many different ways to go about it. 8"x 8" x 18' are heavy poles for certain.

 

[747driver]

I would not fill the holes with concrete up to the top of the hole. Not unless your building code says to due to maybe hurricane codes ? As Oldoak stated...better to put dry mix on the bottom and then back fill with dirt or stone. This lets the water drain better rather than pooling between the concrete and post. If you elect to go with just back fill dirt then nail 2 2x8 treated pieces on the sides of the post at the bottom to help prevent up lift . Any special reason you are using 8x8s ?

 

[Stimw]

I would not want the bottom closed with concrete!
You will be setting the posts in a "Bowl" that will fill with water and rot.
I would set them on gravel or crushed rock so they can weep after the concrete is poured.

 

[TheMan419]

For my barn they drilled the holes then dropped a large pre case concrete 澱iscuit into the hole. They nailed a piece of 2x6 to the bottom of the post. Then just back filled w dirt. Posts are 6x6.

 

[Redlands Okie]

Old oak and stimv have it pretty well covered.

A 3 or 6 inches of gravel at the bottom of every hole. Dry concrete mix right out of the sack packed down with a pole, or tamper of some kind every 9 inches of fill or so. The concrete will absorb the water it needs to harden up from surrounding soil. Even done this in sandy soils of New Mexico and it still happens, just takes longer to attract water.
It will pack a bit better if you pour in a couple of cups of water with each layer of concrete as you tamp it down. I do literally mean a cup or two as in a recipe measuring cup. If you get the concrete squishy wet or semi liquid its way to much water.

Keep in mind that once you add water to concrete and mix it up it takes about 21 days or more for the Concrete to cure. If you start wiggling the post, banging on them while the concrete is uncured your just breaking it apart. The dry mix poured in and tamped down allows you a day or two to hammer on framing or attach rafters. With out messing with the curing concrete issues.

Have seen people do well with back filling only with course sand or small gravel and even just soil. Post almost always rot out at the junction of where the ground quits and the oxygen starts. Add moisture on a regular basis at this point and you have whats needed for fairly rapid rotting sometimes. Other words right at ground level. That’s one reason you often see post mounted on top of Concrete piers or the concrete extends above ground level a few inches on commercial jobs. Sono tubes often used to do this.

 

[truckdiagnostics]

For my barn they drilled the holes then dropped a large pre case concrete 澱iscuit into the hole. They nailed a piece of 2x6 to the bottom of the post. Then just back filled w dirt. Posts are 6x6.

agree not a fan of concrete does not allow water to wick away from post. I filled first 3' with gravel screening mix, then top 1' with clear stone.

 

[GSVette]

Here’s how we braced mine. We poured directly from the chute of a cement delivery truck-well 3 of them to be correct.

 

[truckdiagnostics]

Here’s how we braced mine. We poured directly from the chute of a cement delivery truck-well 3 of them to be correct.View attachment 550697View attachment 550698

unless you are pouring in a sonic tube you are giving the frost a ruff surface to grab onto and push the post up!