Addition On Pole Barn ?

[Autocar]

Which has standard rafters 5 12 pitch ? Any way the lean too I am putting on I want the roof profile to carry right onto the addition. My addition is 20 feet wide by 40 feet long. I would like the twenty feet open rather then have post in the middle of the building . What size white oak would I have to saw to span twenty feet and may have to support a wet snow load ? Or any other ideas what a fellow could do. I have all my 6 x 6 white oak timbers cemented in on the 40 foot side and had planned on setting 16 foot white oak 6 x 6's every 16 feet and laying another 6 x 6 on top to spout the roof rafters to split the twenty feet in half but that eats up a lot of open area. Any ideas what I could use ? Thought about I beams but pretty price goes along with that. 

[Don P]

Things to think about. Half the load will be supported on the existing building, half will be supported by the new posts and beams. The existing beam was not designed to support that nor were the posts. What is the span between posts there and is there an adequate footing under those posts for the additional load? What is the size and height of those posts and how wide is the existing building?

The design snow load for your area is 20 lbs per square foot, add to that 10 lbs per sf for the materials themselves, so 30psf total design load.

the new white oak beam is spanning 16' post to post and is supporting 10' of the 20' rafters, plus 1' of overhang I'm guessing, so 11'. The beam is supporting 16'x11' of area, 176 square feet at 30 lbs per square foot=5280 lbs.

Use this calc from the toolbox;
http://forestryforum.com/members/donp/beamclc06b.htm
I get a pass at 6x12 using #1 material

Building up the beam of 3 pieces of 2x material is stronger because you can see the wood better when grading it and defects are better scattered.  checking that way on this calc;
http://forestryforum.com/members/donp/ddsimplebeam.html
I get a pass with a 3 ply 2x12 beam in #2 white oak.

The post fails in buckling at 15'8" effective height... I conservatively call that from top of footing to bottom of beam length.
figuring a simple column

I'm guessing the existing post has at least double that load on it and is taller than the new ones, that is the ones in trouble as is the existing beam... need to know more about the existing building width, post lengths and post spacings, or you can run a new post and beam setup like described against that existing wall line. Make sense?

[Autocar]

The post are eight feet apart the same on the pole barn. The post on the pole barn are 5 1/2 by 5 1/2 inches and everything I am sawed is true to size. I am planning on bolting a white oak 2x6 x 16 foot to the pole barn post for the whole length 50 feet then when I set my roof rafters they will set on the 2 x 8 that runs on the old pole barn and also on the new 2 x 6 s that I bolted to the building and at the eve end that also will set on two 2 x 6 's one on the inside and one on the out side. Don did I understand what you were trying to tell me No I am sorry pretty much a county boy here I know the sun comes up in the east and sets in the west. I will give it some thought for a few days and will see what I can come up with. Rains every other day so I have some time. I am sure Don you know what your talking about but over the years I have seen number of build that was built a hundred years ago and some of them I even question but even at that there still standing thank you for your time Bill

[Don P]

 Yup, we're missing each other in the translation. It would take a good dimensioned drawing of the existing building and the addition for me to understand what you're doing.