Looking for some Pole Barn framing suggestions

[hkhi]

Hoping someone has run into this problem and can share their experience. I'm breaking ground on a 40x56 pole barn in upstate NY. Plan is for 12 foot walls, using 6x6's every 8 feet, and heavy duty attic trusses in the 40 ft direction with no internal supports. We're in the hills, and our ground consists of 18-24 inches of clay/dirt on top of shale. I'm using a MF1440v with a MF backhoe so the first 2 feet isn't bad, but removing a quarter inch of shale with each pass after that isn't going to work to get down 48 inches below our frost line.

If I don't want to pay several thousand dollars to have 20+ holes drilled through the shale for the 6x6's, and I don't want to put in a complete foundation with footing, what are my options? Can I sit the poles on footer blocks directly on the shale and compensate for the poles only being 2 feet in the ground with extra diagonal bracing in between the 6x6's ? Or is sheathing the whole building in osb required to get the same stability as a buried pole?

If it helps, I also have a TSC Countyline auger for my Massey, but I haven't found a rock auger attachment that's compatible.

Thanks,
-H.

 

[rswyan]

If I don't want to pay several thousand dollars to have 20+ holes drilled through the shale for the 6x6's,

What about renting the equipment to do this (Bobcat or mini-ex + auger with rock drill) and doing it yourself ?

and I don't want to put in a complete foundation with footing, what are my options? Can I sit the poles on footer blocks directly on the shale and compensate for the poles only being 2 feet in the ground with extra diagonal bracing in between the 6x6's ? Or is sheathing the whole building in osb required to get the same stability as a buried pole?

Not sure how much of an issue that it might be, but in addition to shear the matter of uplift (from wind) is something that might factor into a good design and construction methodology. In that respect I think deeper would be better.

There's also the matter of frost heave ....

If it helps, I also have a TSC Countyline auger for my Massey, but I haven't found a rock auger attachment that's compatible.

I wouldn't think that it would be all that difficult to fab an adapter .... or all that expensive to have one fabbed (hex to round or whatever)

Whether the gearbox on the auger could handle it might be another issue though ....

 

[dave1949]

You might deal with it by not putting poles in the ground. Check out these: Concrete footing forms save time, money on renovations, decks & new construction

If you locate your footings, drill into the shale with a hammer drill, insert rebar that will extend up into the footing form, that should solve any shearing issues.

I am not certain you need to worry about frost upheaval, depending on how solid and deep the shale is, it shouldn't be moving with frost.

 

[Army grunt]

>>>>>If you locate your footings, drill into the shale with a hammer drill, insert rebar that will extend up into the footing form, that should solve any shearing issues.<<<<<<
Good thought. Rember its not only to help with frost an shifting, but keep it from flying.You get bad weather up there.
Army Grunt

 

[sdkubota]

AG brings up an excellent point as foundations for large buildings typically have more negative loads (fly away) then bearing lods (weight of building). I am also concerned with the shale as most shales become very expansive once the become weathered. The life of your building will depend on its foundation...not something to go cheap on. Good Luck!

 

[dave1949]

AG brings up an excellent point as foundations for large buildings typically have more negative loads (fly away) then bearing lods (weight of building). I am also concerned with the shale as most shales become very expansive once the become weathered. The life of your building will depend on its foundation...not something to go cheap on. Good Luck!

I have an area with shale about as deep as the OP's. It can be very rotten stuff. A large excavator can pick away about 12"-18" of mine before it gets solid.

 

[sdkubota]

I have an area with shale about as deep as the OP's. It can be very rotten stuff. A large excavator can pick away about 12"-18" of mine before it gets solid.

The introduction to water and time is what "rots" an otherwise sound shale. Drilling into solid material and filling with concrete may slow or stop the introduction of water to the underlying firm shale. Once shale weathers (rots) in turns back into its parent material sediment which is generally very expansive (ability to absorb a lot of moisture and conversely suseptible to significate shrinkage). If I were spending the money I would drill well into the shale and backfill with concrete even if it was below the frost line.

 

[dave1949]

The introduction to water and time is what "rots" an otherwise sound shale. Drilling into solid material and filling with concrete may slow or stop the introduction of water to the underlying firm shale. Once shale weathers (rots) in turns back into its parent material sediment which is generally very expansive (ability to absorb a lot of moisture and conversely suseptible to significate shrinkage). If I were spending the money I would drill well into the shale and backfill with concrete even if it was below the frost line.

That sounds like the method if it is flaking, crumbly, weathered, etc. I guess the OP will have to decide what shape his shale is in, but shale that close to the surface is likely to be breaking up one way or another.

 

[radioman]

If you are intent on doing it yourself then you have two options here :you need one of these Transform a three-point tractor into a drilling machine -- Belltec Industries, Inc. . a regular post hole digger will not work due to no downforce/ proper bit. or get a hydraulic hammer attachment for your backhoe.

 

[hkhi]

Thanks for all the great input. Right now I'm leaning towards the "bigfoot" footers, from what I've read, if I scrape down everything soft and get a layer of concrete on the hard layer underneath it right away (<24 hours), it should seal pretty well. I'm thinking scrape off the soft shale with the backhoe, place the footer with rebar mounted vertically and pour 12 inches of concrete into it. Let it set and then drop the post in place and pour concrete around it to fill the footer and sonotube above it. Planning to backfill with gravel as much as possible to provide extra support around the footer.