size of beam needed for pier foundation

[bent_nail]

I am buillding a cabin in northern Mn. its size is going to be 18' wide by 22' long 2x4 studs log siding roof trusses and shingled roof I wanted to use Ijoists to span the 18' across I planned on corner piers 12" round cement with a center pier so the span for the beam is about 11' on the load bearing sides and about 9' on the ends I would like to use regular lumber and build it on site either double or triple 2x8 or 2x10 or 2x12's anybody have any good ideas or need more information I would be glad to hear from you Thanks  

[skiwest]

I'm doing something very similair.  Actually started out with 20 x 24.  When I used span tables I had 3 rows piers at 9 ' spacing ( 18 outside centers) and the other way piers at 9 and 12 foot.  The 9 foot for where the loft was going to be.

You can use the span tables for deck beam headers like at http://decks-ca.com/Deck_Beam_Sizes.html.  I used the ones at Spancalc2002 which were better as they took into account , whether the beam/header was outside wall, roof load, number of stories, type of wood.  For me that resulted in 4- 2x12s for beams.

Later using WoodWorksSizer ended up with 5 -2x12 for out side beams and 3 2x12s for inside beam.  For that program plug in dead loads , live loads snow loads .  So with my snow load and loft on 2/3 of length I ended up with beefier beams.

That program allows you to size timber rather than just dimensional lumber.

[skiwest]

this might be a good reference   http://www.raisedfloorliving.com/spantables-1.shtml