Pole Barn - Why not use center post?

[blueriver]

Any problems with this design using 2x4x16's? 24" on center?

If your referring to the roof purlins 24" OC ... no problem ... 16' long for the roof is too long. If you go 5' OC ... use 12' material.

 

[gabeancounter]

BR,
Sorry I am jumping all over the place with my questions.

I was wondering about using 2x4 lumber to build the trusses as attached in the drawing above ?

I looked @ a roof rafter calculator and your numbers seem correct - 16' will be a little short for 5/12

 

[Green_in_Michigan]

The building is 30' ... so basicly, without exact calculating ... a run of 15' ... so I see no need to go over a 2x8 ...

So I see you are using the ridge as a structural beam to carry half the load and the run for looking up rafter size in the span tables. Is that it?

 

[LD1]

So I see you are using the ridge as a structural beam to carry half the load and the run for looking up rafter size in the span tables. Is that it?

You and gabeancounter have me absolutly dumbfounded and confused by your posts. I hope the OP is less confused than me.

Building a truss is not rocket science. Go to a place that sells them. Look at their 30' trusses. Take note of the size of the top and bottom cords as well as spacing for the webbing. Just copy a proven design. It really isnt hard.

And sizing rafters isnt rocket science either. A 15' rafter span, L/180 limits, 24" on center, white pine, 30psf live and 10psf dead, minimum requirements are at least a 2x12.

A 2x8 would only span 11' with the above specs. So I DO see a need to go larger.

Your other options aside from a truss would be a 2x10 on 19.2 centers, or a 2x8 on 12" centers.

Spanning 30' is no easy task for rafters. Trusses are much better. And more than likely, cheaper. A Standard 30' W truss on 4' centers probabally uses nothing larger than 2x6's, and would probabally be cheaper to build than the cost of MANY rafters that require larger lumber.

 

[Green_in_Michigan]

You and gabeancounter have me absolutly dumbfounded and confused by your posts. I hope the OP is less confused than me.

Building a truss is not rocket science. Go to a place that sells them. Look at their 30' trusses. Take note of the size of the top and bottom cords as well as spacing for the webbing. Just copy a proven design. It really isnt hard.

And sizing rafters isnt rocket science either. A 15' rafter span, L/180 limits, 24" on center, white pine, 30psf live and 10psf dead, minimum requirements are at least a 2x12.

A 2x8 would only span 11' with the above specs. So I DO see a need to go larger.

Your other options aside from a truss would be a 2x10 on 19.2 centers, or a 2x8 on 12" centers.

Spanning 30' is no easy task for rafters. Trusses are much better. And more than likely, cheaper. A Standard 30' W truss on 4' centers probabally uses nothing larger than 2x6's, and would probabally be cheaper to build than the cost of MANY rafters that require larger lumber.

I agree with you.

This thread has centered on re-engineering solid designs in order to save money - not advisable for the novice builder. One poster suggests using 2x8 to span 30 feet. Unless there is some structural condition I did not understand how he can recommend that number. That is why I asked if the ridge board was a structural member. The OP should consult his local building inspector for acceptable advice or risk having to rip out everything he put up. Do it simple and do it right the first time.

In Michigan you are required to have a licensed firm build your trusses. Or have a licensed engineer certify your design. The local inspector will ensure you have followed the correct fabrication.

I will say that I think some builders are better than engineers when it comes to the practical side of building and fabrication. You are probably one of them. I will leave this thread with just cautionary advice that if you don't know what you are doing you should not redesign anything to save money. I just don't want anyone to get hurt.

One more short item. The center posts picture appears to use large lam beams for connection to the post and the outside header. That would be post and beam construction and a whole different animal that plain framing.

 

[LD1]

I just realized gabeancounter IS the OP.

Confusing as ever:confused2:

 

[gwjd]

do not say now snow in GA you never know
also

southern winter-storms are ice and sleet that is much heaver per cubic foot


so not saying you need trusses set up for Maine but thinking a little farther north is not a bad idea

 

[blueriver]

So I see you are using the ridge as a structural beam to carry half the load and the run for looking up rafter size in the span tables. Is that it?

Thats when the OP was thinking center poles ... that would create a ridge plate and the use of 16' 2x8 rafters ... also keep in mind knee braces distrube the roof load.

One poster suggests using 2x8 to span 30 feet. Unless there is some structural condition I did not understand how he can recommend that number. QUOTE]

Read back ... I never made any such suggestion. As I stated the building span is 30' ... thus the run for rafter calculation is 15 ... you are correct that you can not span 30' with a 2x8 ... I do believe with the center post design and a ridge plate and proper braces the rafter can be 15'10 4/12 2x8

 

[bearcreek paul]

Hopefully the pictures help i could not send them from my i phone.By the way i changed the design a bit.

 

[blueriver]

Hopefully the pictures help i could not send them from my i phone.By the way i changed the design a bit.

There ya go ... I guess the webbing doesn't have to be angle cut and use plywood for a gussett ... just cut them to length and nail them along side the top and bottom chord.