Pole Barn problems

[logguy]

I have the treated 6x6x16 posts installed, 3' deep and 8'-9' apart, in a 27x32 footprint, as shown. This was just going to be a simple pole barn, gable ends on each 27' side with a 4-12 pitch and 5 store-bought 28' trusses. But I've decided to make the structure twice as big, AFTER I have installed the posts shown in black. I need to enclose just the left side (shown), and lengthen the 27' gable ends to 54'. The trusses were going to span the 27' interior (plus a 6" overhang) with no interior support, but now, rather than go with trusses, I think I can just use two more posts for interior support, placing them as indicated in the drawing on the left side, and later add the additional posts, shown also in red, on the right side.
Suggestions? Is this design structurally strong enough using 2x8s where indicated in blue, and later in the same manner when I build the open side of the barn onthe right? Am I spanning too great a distance with 2x8s? Is there a better way of doing all of this now that I have the posts (shown in black) already installed?
<img src="http://twistytreeranch.com/pb15sep10.JPG" alt="Modified pole barn" title="Modified pole barn" width="390" height="398" />
<a href="http://twistytreeranch.com/pb15sep10.JPG">http://twistytreeranch.com/pb15sep10.JPG</a>
Thanks much!!

[edkemper]

Perhaps some of the engineers can answer your question but as a group, we don't do pole buildings. We build real logs homes in the butt &amp; Pass method. However, welcome to our site.

[logguy]

Yes--I'm aware of that. I'm a member. :)
I remember a table shown in class that had spanning distances for 2x6s, 2x8s, 2x10s, etc., but I can't find it in the book or on the CD.
The greatest distance I am spanning in this alternative structure is 18' and the only thing that needs to be supported above that 18' is the tin roof/medium snow load, here in MO, on top of 2x4s every 2 feet. I understand that placing three posts where I plan to place just 2 posts (shown in red) within the current footprint would PROPERLY support the roof, but I suspect that supporting a roof rafter that's NOT directly over a post may still be over engineered because the span between posts is still just 10' or so. This is my main question for you smart folks, along with the 18' span. Will 2x8s do it?
I'm still sticker-shocked with the reality that even though we can build a very cool, very over-engineered log cabin, very inexpensively with the LHBA B&amp;P methon, the cost of the foundation (and eventual roof) is still what's holding me up...not to mention having the time to actually get going on anything substantial. I have plenty of land but that's as far as I've gone, so far. My hat's off to you and everyone who has gotten off the ground--and of course completed--their real log cabin.
Cheers!
John

[edkemper]

Duh! My mistake about you already being a member, Sorry.
Hang in there. Don't be in a race. Build as you can afford anyway you choose. The most expensive part of my home will be the roof. But that roof will be the most important part of the whole project with an eye toward our family's future costs.