Barn pier foundation questions

I have been thinking about replacing our 28x48 pole buiding in
2015 and I have been trying to find out about foundation
options. The current pole barn has 6x6 poles at 12' spacing.
The trusses were homemade by the last folks who lived here and
are sagging badly and I would like to have an enclosed building
with a loft instead. I can saw all my own lumber and reuse the
existing roofing tin. What I would like to do if it is reasonably
possible from an engineering point of view is to use 8x8 posts
set on piers above ground at a 12' spacing. It would be much
less digging than a full foundation with a footer all the way
around the building but I have not been able to find many
references to building this way. I see lots of designs for pole
buildings up to 50 feet wide but they are all single story and
have truss roofs. I do not want to set poles in the dirt for a two
story building because they would be very hard to replace when
needed. If anyone can tell me if my idea is practical and where I
could find out how large of a footer each post would need I
would really appreciate it. I am hoping this year to get most of
the lumber sawed out and be able to get going in spring 2015 so
I have plenty of time to figure out a plan. Thank you very much.
Zach

Your building code may dictate what you can do. My builder bored 18" holes about three feet deep,below the frost line. He poured six inches of concrete into each ,tamped down and let set. The posts then sat on top of the cement and they were every 8'. Posts were PT. Setting a pole barn on piers above ground doesn't really anchor it to my way of thinking,posts set in 3' on concrete does anchor when they are back filled and tamped. Also when setting the posts ,you can move them an inch or each way to help line up,they are easy to move sitting on their concrete pads

I don't know if this would work for you, but they use a lot of these around here.
https://www.permacolumn.com/

12' spacing sound like a lot! You did not tell us where you are located. Frost depth, snow load, exposure to wind, there are lots of variables in putting up a building.

Have viewed several of the type listed below and does not look like a bad idea. I am betting if you set good PT 8 in post doubt that you would ever have trouble in you lifetime but the post on concrete deal is pretty slick. Plant near me making them and they are really selling.

Properly treated posts, installed correctly, won't need replacement in your lifetime. But you can set posts in brackets on concrete piers if you like. The piers need to extend below the frostline and be large enough to support the weight on the post.

A 12' span between sidewall posts is pretty wide even for a single story building. And you'll need interior posts to support a second floor.

Lots of info in the National Frame Builders Association's "Post-Frame Building Design Manual".
NFBA Post Frame Building Design Manual

Thanks, I should have said that code does not apply to this building because it will be used for "agricultural purposes" according to the code enforcement officer in our town.
Zach

I've looked at them and they do look interesting for sure.
Zach

Yes, it does seem like a lot and I am not attached to that spacing, that is just what is there now. I am in northern NY so we do have snow but not as much wind as in some areas. 4 feet is more than code calls for here so I have figured it was deep enough.
Zach

Probably it would outlast me but I have heard a lot of differing opinions on the post treatment and don't know who to believe about it.
Zach

Thanks, that manual is very detailed and may be more than I can digest but I will certainly try. 12' seemed common in some pole barn plans I looked at but they were single story and I wouldn't mind changing the spacing. I had figured on a row of interior posts down the middle with 3 or 4 2x12s making a beam on top of them and the floor joists on top of that, but even that may not be sufficient, I don't know.
Zach

A pole building relies upon the pole for several different things.

It needs to carry the roof and everything on the roof. A lot of weight. If you are on 12 foot spacing you must be in the south, up here in snow load they go with 6, 8, or 9 foot spacings.

It needs to take the side load a strong wind puts on the pole. So it depends on your winds, but who doesn't get a 70mph downburst every 50 years or so, so we all need good wind ratings.

It also needs to take the upward pressures of the wind in your area. I have seen several buildings that were pulled out of the ground in a tornado or microburst, as the wind got in a door and lifted it up like a balloon. The machinery all sat there, with the building crumpled 100s of feet away.

So for such a wide spacing, 12 feet, the wind rating becomes interesting. You won't have many poles to take that side pressure.

Now you want to put the pole on a pier. That puts a joint there on the bottom. That really really weakens your pole. So to keep your wind rating, you need a really strong connection between the pole and the pier. This will be the critical thing. It needs to take the sideways and upward ratings your building will get. And the taller you make the building, the more stress this joint will have.

A stick built building with a full foundation has many attachments, every 16-24 inches, to the foundation so it is easier to make that joint nice and strong. Your pole building, especially with a 12 foot span, is going to really stress that joint. Your old building with the poles in the ground, has a flex and grain through that joint area. Your new building with the pier is going to want to bend and stress right at the joint.

Just what you need to focus on, the weak point of your design.

Paul

price those perma colums and you'll probably want to do something else,..they are $90.00 apiece around here,...I did my own using 6" pvc pipe and pouring them full of concrete

Meet with your lumber supplier. They'll either have an in house engineer or their suppliers will. They can design your building to meet your needs.

The way I read the question he is sawing his own lumber and reusing the tin. So his lumber supplier is him.

I to am looking to build another storage building. It will be a 28x28 timber frame with up stairs for storage or another 30x40 pole barn. If I go with the pole barn, my plan is to use 3 pressure treated 2x6 for ground contact, stagger the joints and use white pine from my saw mill to make up the rest of the post. Pressure treating only goes in the wood so far, a pressure treated 6x6 pole is not pressure treated all the way through. 2x6 should be pressure treated all the way trough. As for plans, Google LSU AG Center.com , pick the publications category and then type in pole barn plans in the search box. They have a huge array of down loadable files.

I think you need to look up Perma-columns. I think that is what they are called.

Make sure your posts have enongh chemical. Lumber yard poles many times do not have enough for a permanent building;
“NatureWood” Alkaline Copper Quaternary ACQ
Minimum 0.60 pcf for Structural / Building Pole / Foundation Use

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

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

My machine shed is put up the way you describe. It is 40x50 with about a third of it having a "loft". That i very nice for long-term storage. The rest is tall enough to drive in the cab tractors with two tall doors. The poles are telephone poles. The trusses are scabbed ones and they are looking a little ragged. This metal roof is insulated so it doesn't sweat but the one before it sweat all over and ruined the plywood scabs. The whole shed has 8" reinforced concrete so I can put anything on it. Both of my big sheds are solid concrete floors and that is a mistake. Leave yourself a good portion of dirt. Being cemented the tin sides go right down to the cement line to seal up.

look around your neighborhood for old barns that are still standing and looking good. ask the owner if you can take pictures of the constrution along with measurements. depending on how old the barn is it will have built up posts and beams made from rough sawn lumber or older will be solid posts and beams. you want one that is new enough to be built with rough sawn lumber spiked together to make the posts and beams. also remember that they will have a slate roof the weight of which holds them in place against the wind. you will be surprised by the foundations as a lot of times it will be one sandstone block under each post.
remember if it is still standing and looking straight and good then somebody built it right the first time for YOUR AREA

good luck
Ron

Built 64' by 88' last year. 8' centers with perma-columns. Best way to go. Thanks Steve

(quoted from post at 15:05:26 02/24/14) Make sure your posts have enongh chemical. Lumber yard poles many times do not have enough for a permanent building;
“NatureWood” Alkaline Copper Quaternary ACQ
Minimum 0.60 pcf for Structural / Building Pole / Foundation Use

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

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

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That's the ticket. You have to get the correct treated wood if you want it to last. It would mean ordering it, I'm sure. But if the drainage is decent and it's the good stuff it will surely last a lifetime. I've seen treated wood that's been in the ground 40years now that looks like new. Back then it was all the "good stuff".