40x60 pole building footings

[conceptmachine]

Hello,
Thank you for the info in advance. I'd like some expert opinion on what is needed for footings on a 40x60 pole building with 6" posts 8' on center. I'm in iowa so winters get bad sometimes. The ground is river bottom that has a mixture of gravel, sand and black dirt. I'm going to build up the ground about 2.5 foot so that if it floods I'll stay above it...so roughly only be about 2.5 feet deep into the original ground. Not in a flood plain however, just being cautious. What size, psi, and what method should be used for the concrete footings?
Should the posts be tied into the footing or should it float on top of it, and what's the benefit of either?
Thank you again.
Jim

 

[magnumdeke]

I would determine normal frost depth, here in Mi. 42" is the norm unless there is a high use driveway next to the building, Drill holes to 48"deep 18" diameter, pour a 6" concrete pad in the bottom and tamp flat.
To prevent upheaval of the post you can cut 2x4 blocks and nail them to the bottom sides of the poles or I prefer to auger a 1/2" hole through the pole say 4" up from the bottom and put a 12" piece of half inch rerod through it.
When you bury the pole pour a full bag of sack crete around the pole encasing the rerod in it.

 

[southernfriedcj]

, Drill holes to 48"deep 18" diameter, pour a 6" concrete pad in the bottom and tamp flat.
To prevent upheaval of the post ... auger a 1/2" hole through the pole say 4" up from the bottom and put a 12" piece of half inch rerod through it.
When you bury the pole pour a full bag of sack crete around the pole encasing the rerod in it.

This is what I did, but I poured my post base concrete 10" thick and used a ready mix truck to pour the concrete around the posts.

 

[magnumdeke]

This is what I did, but I poured my post base concrete 10" thick and used a ready mix truck to pour the concrete around the posts.

Ya, we do that for buildings with a high wind lift factor, such as curtain walled ag buildings where wind can get under the roof. It would be the caddilac way for a garage. Just adds some complexity with the bracing necessary to hold the poles plumb while pouring the concrete.

 

[conceptmachine]

Hey fellas, thank you for the information. I've heard varying opinions on weather to set concrete around the post. But i also don't want the structure to lift. I'm going to have a 8" concrete floor so maybe I can tie into the posts there, do you think that would work? Or would it sometimes rest on those rather than the pads? Probably crack the heck out of the floor.
I was debating on just putting full 4 foot walls in with footings. Wonder what that would run? Arm and leg probably.

 

[magnumdeke]

All depends if you put a frost wall in along with the pad, 1" foam board all around the perimeter with concrete, mini poured wall or thickened edge.
Are you gonna heat it? outside perimeter of a basic pole barn slab will move up and down with frosty ground with out a frost wall and heat. I always let the slab float and try to keep the poles stationary, not tied to the slab.
Your bottom skirt board should be two inches below top of floor which helps with avoiding any air gaps at the floor with floor or pole movement with frost.
IE a ten foot tall barn measures 10' 2" from bottom of skirt board to top of support board.

 

[conceptmachine]

Thank you,
I plan on using in floor heat, ran off 3 phase power.

 

[conceptmachine]

How high do you cover the post when it's resting on the pad witch concrete ? All the way to ground level?

 

[magnumdeke]

How high do you cover the post when it's resting on the pad witch concrete ? All the way to ground level?

In your situation I would only use a bag in the hole around a pin through the pole,(DRY ground moisture will harden it) If you want to fully encase the pole you would want to fill the hole to just below finished exterior grade so you dont have to see it, can finish with grass or gravel to the bottom edge of the skirt board for a clean finish.

 

[conceptmachine]

In that case, if it doesn't make any difference I'll just do a bag of Crete at the bottom. I was thinking full concrete would give better life of the post. If it does I'd rather encase...this way at least I have a selling tool for the next buyer 30 years from now.
I appreciate your help very much.

 

[conceptmachine]

If i do the full concrete, should I still pin it?

 

[magnumdeke]

pin it either way

 

[conceptmachine]

Thanks Magnum!! Will do, think I'll just do the bag in the hole. Saves s bit of headache and won't make much difference.

 

[kbs2244]

The best pole building info site on the net.

http://www.pole-barn.info/pole-building-construction.html

Download the PDF

 

[conceptmachine]

Thanks for the link!!!!