I assume that the truss designer is aware the your spacing plan?
The truss between the 12'6" bay and the 8'6" bay will be carrying more weight then any other one.
Pole barn roof question
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I assume that the truss designer is aware the your spacing plan?
The truss between the 12'6" bay and the 8'6" bay will be carrying more weight then any other one.
Yea so im guess im just gonna go with 2x6's for them larger bays and 2x4 in the smaller bays just to be safe. Yea the guy that designed my barn is aware of the spacing. I am using double trusses for this project. so should be pretty strong
do they make 4x4 hangars or did you just toenail them into the truss?? and how did you space them?? 2' oc or a larger space. Did you actually save money by buying 4x4's rather than using just a 2x6.
Rowdy Raven
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I am not sure if they make 4x4 hangars or not. I think that I have seen such at Lowes. I used a steel truss that was welded out of 1.5x1.5" angle iron. The trusses are 10" high and 20' long. I predrilled them on 30" spacing and used 3"x3/8" lagbolts to secure the 4x4s to the trusses. Where there were lap joints I ran a carriage bolt from the top through the two 4x4 tounges and then through the steel truss and then put on the washer and nut. This may not be conventional but it sure did work well. I can walk around on the roof and it does not flex. I will try to post some pix when I go back up this week.
sweet sounds like a pretty solid idea!! yea i would love to see some pics
rambler
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Wow - not an engineered building, huh? Don't have a good feeling about the mis-matched spacings, that doesn't come out so good long term.
You don't live in snow country, I hope.
Up here in MN they use southern pine 2x4 Good grade, not construction or SPF junk) on edge over the top to span up to 9 feet. Don't know what to tell you on an irregular building like that, 12 foot span is unheard of on a wood building, they would do a 8 or 9 foot spacing and keep the roof trusses at regular spacings, put in cripple posts and big headers to span the doors.
Got a Bostich paper tape frame nailer tht does the short fat connector nails, works well. Sure would hate to try to pound those little fellas by hand, if you go with metal straps.
Saw more of the thread now, didn't all show up when I started replying. Guess you got it approved that way, with odd spacings. Huh. That's something different, don't see that around here. Snow would mess that sort of structure up in a few years, un-equal loading....
--->Paul
It's very common around here. Huge freestall and livestock buildings mostly. They typically use the LamPly brand trusses then.
Why? If the rafters/trusses are designed for the extra load there is no issue.
You could space the trusses 24' o.c. and use 2x12s for purlins if you want.
beppington
Elite Member
Can ya'll help me with terminology? I keep reading "purlin" on the various barn threads, but don't know which piece that is ... ?
A purlin sits on top of the rafter/truss and runs perpendicular (parallel to the ridge). If you have rafters 2' on center and sheathing, you don't use them, but if you have a metal roof, you don't need the sheathing so you need something else to fasten to. If the rafters/trusses are too far apart to use 1x or 2x on the flat, you can stand them on edge to make them stiffer. There are several ways to use them. Most common is simply on top of the rafters, notched and inset was used a lot in the old post-and-beam, or hung off the sides of the rafters with hangers which is what these guys are talking about. While you can't use longer stock and span several trusses that way, it does mean the roof is closer to the trusses so it makes a little better use of the internal space, especially if you have a loft or attic.
Or if you prefer, sort of like a girt except on the roof instead of the wall.
jml755
Silver Member
First off, I'm no engineer, but every pole barn I've been involved in building or seen around here is Michigan has 2x4 purlins laid flat with usually 4' OC spacing on the trusses. I've seen some with 2' OC truss spacing as well. 8 ft? I don't know about that. Would seem to create an awful springy roof and tough to compensate for to save a few bucks in trusses on such a small building. I know I wouldn't build a P.B with 8' spacing.
The issue of trusses being over a wider span (like a door opening) is addressed with a proper sized header above and across the opening and stub post(s) between that header and the header that the trusses rest on. Usual 10' door openings here have 2 - 2x10s as a header. 12' opening? 2x10s might do it or go to 2x12's. Or you could look into glue-lams which I have no experience with but are are being used more and more as structural replacements for solid lumber. It shouldn't be hard to figure out what you need to span 12' and carry the roof load. In any case, it seems that your slightly larger than normal door openings are driving you to costly and complicated roofing decisions when I don't believe they need to.
The issue of trusses being over a wider span (like a door opening) is addressed with a proper sized header above and across the opening and stub post(s) between that header and the header that the trusses rest on. Usual 10' door openings here have 2 - 2x10s as a header. 12' opening? 2x10s might do it or go to 2x12's. Or you could look into glue-lams which I have no experience with but are are being used more and more as structural replacements for solid lumber. It shouldn't be hard to figure out what you need to span 12' and carry the roof load. In any case, it seems that your slightly larger than normal door openings are driving you to costly and complicated roofing decisions when I don't believe they need to.
beppington
Elite Member
OK, got it, thank you! :thumbsup:
Thick82558
Member
I have built many pole buildings and am a carpenter by trade. Yes you can span 12' with a 2x6 2' oc. You also put the perlin on edge not flat flat dose not carry load. On edge dose. Example place a 2x4 flat not on edge on a five gallon bucket then try to walk up incline the board would either bend significantly or bust. But on edge you could walk up it. On edge is where strength is. The double truss works great it is on either side of treated 6x6 as far as hangers we use scrap 2x6 material cut 10" long or so. Shove between double truss as it is same width. Nail 5" hanging above truss then the rest goes in between double truss nail off on each side of truss. Then put pearl ins on they rest on that scrap that sticks up 5" above truss then nail to scrap 2' oc repeat till done hangers work just more expense and more work.
I would venture to say that 7 or 8 out of 10 post frame buildings are built with trusses 8' o.c. There are literally thousands of them around here. I would not build a building with trusses sitting on header instead of the post where it belongs unless necessary like a door opening.
jml755
Silver Member
Thick82558,
If I understand your post, you put a truss on either side of a 6x6 post at the wall. This creates a nominal space of 6" (actually 5.5 or so) between them.Then you put a scrap 2x6 every 2' going up the middle of the gap between the 2 trusses, correct? (Shove between double truss as it is same width)These "hangers" are perpendicular to the roof edge of the truss, i.e. they're not plumb, correct? And they stick up ABOVE the truss edge 5"? (Nail 5" hanging above truss then the rest goes in between double truss nail off on each side of truss)Then you nail the purlins to the TOP (or side) of those scraps so the roofing material is actually 5" or so away from the truss top edge? (Then put pearl ins on they rest on that scrap that sticks up 5" above truss then nail to scrap) Am I interpreting your words correctly?
If so, please explain the advantage of putting the roof surface so far away (5") from the structural part of the roof. I would think that heavy snow loads would tend to stress those scrap "hangers" in a down-roof-slope direction. Don't know at what point you'd get a roof failure, but without some clear-cut advantage, I can't see that it's worth the extra time and effort ($$) to do this.
Plus your statement "Yes you can span 12' with a 2x6 2' oc." may be technically true, but at what load rating? Seems that 12' span would be at very minimum live/dead load ratings. Would it pass code?
If I understand your post, you put a truss on either side of a 6x6 post at the wall. This creates a nominal space of 6" (actually 5.5 or so) between them.Then you put a scrap 2x6 every 2' going up the middle of the gap between the 2 trusses, correct? (Shove between double truss as it is same width)These "hangers" are perpendicular to the roof edge of the truss, i.e. they're not plumb, correct? And they stick up ABOVE the truss edge 5"? (Nail 5" hanging above truss then the rest goes in between double truss nail off on each side of truss)Then you nail the purlins to the TOP (or side) of those scraps so the roofing material is actually 5" or so away from the truss top edge? (Then put pearl ins on they rest on that scrap that sticks up 5" above truss then nail to scrap) Am I interpreting your words correctly?
If so, please explain the advantage of putting the roof surface so far away (5") from the structural part of the roof. I would think that heavy snow loads would tend to stress those scrap "hangers" in a down-roof-slope direction. Don't know at what point you'd get a roof failure, but without some clear-cut advantage, I can't see that it's worth the extra time and effort ($$) to do this.
Plus your statement "Yes you can span 12' with a 2x6 2' oc." may be technically true, but at what load rating? Seems that 12' span would be at very minimum live/dead load ratings. Would it pass code?
jml755
Silver Member
You may be right on the percentages, won't dispute that. But the only ones I can think of where they've used 8' spaced trusses here in Michigan are very large buildings (160'-200' long) where the trusses span 60-80 ft and are therefore pricey. I'm going to check one tonite but I think they rest on the headers there. I've also attached a picture that is typical of pole barn designs I've seen. I'm building a barn addition right now with the rafters sitting on headers, per code.
And for a 50' long building you'd need 14 trusses 4' OC. For 8' OC you'd only need 7. Not much savings in my mind, probably less than $1000. And resting them on the headers means I don't care if the post spacing is not EXACT. Heck, my line posts can be off a couple of inches and my headers and girts will compensate for that. How many of you have set 16' long posts in the ground and got the tops to be precisely where you want them and then not move during construction? Sure, it can be done but it's a lot faster and easier to set them without worrying about that. And if you're sheathing the roof, it IS important when installing the trusses that you get a perfectly square roof . Using purlins you can be off some on the spacing or even squareness as long as your corner posts are perfect.
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Thick82558
Member
Yes it passes code I have built many and all have passed inspection. The 2x6 on edge sets on the truss the back of perlin rests on the 2x6 sticking up. There is is no air space between prelin and truss. It's hard to explain I will try to take pictures. Here in Oregon it is rated for 2' snow load I don't know what your load rating is in your neck of woods but a 2x6 on edge has and will pass building code here in clackamas county Oregon which gose up to 13,000' in elevation.
Are you saying code says they have to set on a header? Because I can set them on the post per code.
I just ordered 40' trusses @ $240 a piece for 8' spacing. Not only will the truss set be cheaper you will not need the header material, and labor to install.
As far as wild spacing it doesn't make any difference this way either when you set the purlins on top of the trusses. But then I don't find it the least bit difficult to get the trusses spaced accurately.
I don't find using 2x4s this way to be the least bit spongy or springy, especially when set over the top of the truss in a compound span.
Thick82558
Member
This is what I am talking about building.
jml755
Silver Member
No, I'm not. Set them wherever you want. I'm just saying that a header carries the truss load TO the post AND will pass code. My response regarding headers was to address the OP's 12' opening "problem" and his seeming intention to have his trusses spaced at 12' at that point. I just wanted to give him a simple solution that is well documented as acceptable pole barn design. Using a 2x6 on end 2' O.C. across a 12' gap is marginal at best. I just took a quick look at a span table and even for light loading 10' or 11' seems to be the limit. Not trying to say YOUR method of building is wrong, but insisting that a truss be on a post doesn't help him with a 12' opening. Plus, he stated his trusses were only around $100 each.
Marginal? Anything but. It is no better or worse then a 2x4 on 8' center. Both 2x4 on 8' and 2x6 on 12' are a "simple solution that is well documented as acceptable pole barn design".
[/quote] but insisting that a truss be on a post doesn't help him with a 12' opening. Plus, he stated his trusses were only around $100 each.[/QUOTE]
I never implied that his truss couldn't set on a header. Insisting that he can't have a 12' span is even less helpful. Must be one of these I have never seen or done it so it can't be done.
