Need help on trusses 9' on center or 4' on center for pole barn

[Cedar Point]

Should I go with a truss span of 9' or 4' span? Every company says different things.

 

[Fossil Farm]

Depends on snow load, wind load, roof weight, etc. Around Lake Erie and what I have seen, if the price is not too much more, depending on the size of the structure, I would go 2 foot on center. One barn we have is 4 foot on center and the house addition is 2 foot on center. Should have gone with 16 inches on center for the house for a more rigid roof frame. The additional trusses on the barn would not have been much more, and 2 foot or 16 inches on center would have been nice. Especially with the quality of wood available for trusses these days and the common use of 7/16 OSB for a shingle roof on many smaller barns.

 

[KennyG]

I never quite understood 9 feet since it's an odd number. I think the choice is between 8 feet and 4 feet. Either works. 8 feet will be cheapest. If you ever intend on insulating and installing a ceiling, go 4 feet. Liner panel can span 4 feet but not 8.

 

[Cedar Point]

Should I go with a truss span of 9' or 4' span? Every company says different things.

Thanks - 40x64 14' tall metal roof. Posts or laminated beams?

 

[GManBart]

Thanks - 40x64 14' tall metal roof. Posts or laminated beams?

Are you putting the posts/beams in the ground (set in concrete, of course) or something else (posts on top of concrete pillars, foundation) etc?

 

[BHD]

the truss can be designed to carry the same load either spacing, basically the spacing would have to deal with the purlins, used, and the size of them to carry the loads, so if cost is the issue figure both roof systems to make your decision,

some may also consider the ease of putting up ceiling materials, if desired,

I like to see some closer spacing my self, (OK it seems like if you have wide spacing and failure would occur disaster happens, but on closer spacing one can fail and the others help support until repair can be accomplished many times),

My two cents,

 

[Cedar Point]

Don't you have to lay a purlin on its edge on a 9' application. How would you get a good grip on your metal roof...?

 

[KennyG]

Don't you have to lay a purlin on its edge on a 9' application. How would you get a good grip on your metal roof...?

Yes, roof purlin on edge for 8 or 9 foot spacing, flat for 4 foot spacing. Supports the roof fine either way but you have less of a "target" for the screws if they are vertical.

 

[duke7595]

Should I go with a truss span of 9' or 4' span? Every company says different things.

For what it's worth I would not go less than 4' O.C. especially with the 14' walls, think in the long term. Good luck.

 

[RickB]

If the snow and wind load ratings compare favorably, it doesn't matter. Pole barns are not 200 year structures no matter how much lumber is used.

 

[s219]

There is so much to this decision, including snow loads, uplift loads, etc. Normally what I do is start with the desired metal, which will dictate spacing of rafters and purlins for loads (wind uplift in particular is sensitive to screw retention and spacing). Then see if those loads transfer down to the header beams and post footings OK. In the end, it all has to be right.

For my recent boat house project, I used 26 gauge PBR panel. Knowing the typical uplift (in PSF), needed to handle wind loads, dictated the screw spacing, and that in turn dictated 24" spacing of purlins and rafters.

 

[JerryK]

You have to think ahead on how you want to work up in the ' attic ', too. I have walkways up in my 80' long 4' CTC so I can work up there, and the 4' help support wiring/conduit. If you plan on using a lift to access that area, then the 9' openings would be nice... The 4' give you more things to try to grab as you plummet towards the hard concrete ..!!! My barn is also striped with 2x4's 2' CTC length wize that my insulation is screwed to. The 4' CTC is better if you ever plan on installing a ceiling. If you do, you will be amazed how huge the ' attic ' is when you go up there... [ and all the $'s worth of 2x4's and trusses that's up there ]

 

[EddieWalker]

I like to put my trusses every 4 feet. That gives me a very solid roof, allows me to put my purlins on the flat, and I can still insulate between them or span that distance for a ceiling using metal. While a lot of commercial buildings will go farther, I think having the purlins on the flat adds enough strength and ease with installing the metal that's it's worth the extra expense.

For posts, I feel that a pressure treated 6x6 is still the best choice. I'm not a fan of using 2x6's at all. Having a post in the ground 3 to four feet gives you a lot of strength. Finding 2x6's that are rated for going into the ground is going to be difficult. I've never seen them, but from what I've read on here, you can special order them. How long do you have to wait, how much do they cost and how straight are they when you get them? If you go with regular lumber and install them on top of concrete, you are creating a hinge at the mounting point that you have to compensate for in your framing with additional bracing to make it stronger. More money, more work instead of just using a treated 6x6.

Eddie

 

[rrrkkk]

mine is 36 x 40 x 14 it has 8' between trusses. I installed a metal liner panel and had no trouble at all with 8' spacing. On one side I put a 40' LVL beam and supported an 8' loft on one side

 

[TBarD]

If the building is not too tall 6x6 treated will work fine, but for taller buildings (eg 14' or more) it may be necessary to go with 2x6 or 2x8 laminated posts. These should be engineered glulams however, treated on the end that goes into the ground. They are likely to be a special order. Re truss spacing, any spacing will work so long as the building is engineered for the local snow and wind loads. If the building is not engineered, for sure you want to overbuild it, e.g., the usual 8' post spacing with trusses 4' on center. Personally, for any larger building in snow country I would want it professionally designed. For a smaller building I would be tempted to just go with a conventional design and overbuild it. Lots of places though, will require an engineered design, to get a building permit these days.