need help with Post and Beam size.

[joe w.]

I need help with simple post and beam framing. i want to build a post and beam straw bale home. i have read of folks who have used 4x4 post uprights every 8 ft., besides of course more around doors and windows. then using 2 2x8s nailed together for cross beam. they say putting on galvalume roofing its a lot less weight so the 4x4's are plenty strong enough. plus using 1 and half to 2 inch stucco inside and out on bales strengthen it also. home is about 23x45 ft. with loft on each end. is this safe or are they pushing their luck? need to know if this is ok before i start building mine. please help with guidence on this issue, thanks, joe w.:confused:

[Don_P]

Hmmm, that's going to be tough to do without an engineer, you are beyond the prescriptive allowances of the building code so engineering of some sort is required. The loft on each end sounds like you'll have to have a load bearing midwall. The section in between still needs to be tied side to side or a ridge beam between the lofted ends. The 4x4's and double 2x8's sound mighty light if there is a floor plus roof load involved.

As an example 8'x6', assuming the midwall under the loft=48 square feet X 40 lbs per square foot =1920 lbs, so there's a ton on the beam. The roof is an unknown without snow load info but lets look fast at one scenario, here it would be 20 live load + 10 dead load so 30 psf X 12' (half the roof span)X8' (post spacing)= 2880 lbs... here that double 2x8 has 4800 lbs on it. That is also the post load. I'm failing up until a double 2x12 in #2 SYP that quick string of guesses. You should probably find a design professional.