Thanks for the read, I am at a little bit of a possible problem. I recently built a 72’ long by 48’ wide post frame shop. I was originally planning on using one truss on every post and running purlins like the YouTube channel I have been watching. After talking with the truss manufacturer, they said the only way to get the trusses to pass was on 4’ centers, because of where I’m at in Montana. I decided to run two 2x12 #1 southern yellow pine header boards on each side of the post and fasten them with a large handful of .148 4-1/2” ring shank nails and a few 5” lag screws. Doing this allowed me to run my trusses on 2’ centers and get rid of the purlins and just use 5/8 osb sheathing. I also used a wood block every 2’ to fasten the truss to and tie the header boards together. I am currently thinking another 2x12 underneath the inside 2x12 would be a good idea? I have two 10’ garage doors that would be my largest span for the header boards to carry. Every other span is 8 centers or less. I made 4 ply 2x6 posts 5’ deep with 20” concrete piers and perma column brackets, 16’ tall walls. The would appreciate someone’s opinion on whether or not this will be strong enough to carry some snow load through the winter without collapsing on myself. Very appreciated!
Need help with my post frame header board size and strength!
- Thread starter Jordan1
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jack stand
Well-known member
Are the 2 2x12's that support the trusses only supported by fasteners, with no direct bearing?
There's only so much space at every post to put nails & heavy screws to do all that work.
I might be thinking about adding a 18" LVL as long as possible directly under the inside 2x12. That will help with the span between the posts and provide an additional space for a lot of "structural screws".
If the post's are notched and there's a direct bearing seat of the top "beam" you're probably ok but I'm not sure how much snow you can end up staying on the roof or that doesn't blow or slide off.
Ideally you'd carry that load down to the footer or column base not solely relying on the shear value of your fasteners.
There's only so much space at every post to put nails & heavy screws to do all that work.
I might be thinking about adding a 18" LVL as long as possible directly under the inside 2x12. That will help with the span between the posts and provide an additional space for a lot of "structural screws".
If the post's are notched and there's a direct bearing seat of the top "beam" you're probably ok but I'm not sure how much snow you can end up staying on the roof or that doesn't blow or slide off.
Ideally you'd carry that load down to the footer or column base not solely relying on the shear value of your fasteners.
billconner
Well-known member
Using the 40 PSF from truss drawing for snow load, that's 9600 pounds evenly distributed on the 10' headers. I don't think your two 2x12s are close to that. Google AI says double 2x12 10' just 1400 pounds. IRC only goes to 36' wide building but in your snow load, double double 2x12 would only span around 6' - and your load is a third more. Just looking at tables, 36' wide building with 30 PSF would require a header with four 2x12.
Lumber yard can tell you what LVL for 960 a foot for 10' but probably in the 3 1/2" x 14" range.
Too late but for others if trusses 48 on center work, two at 96 would work and no headers.
Lumber yard can tell you what LVL for 960 a foot for 10' but probably in the 3 1/2" x 14" range.
Too late but for others if trusses 48 on center work, two at 96 would work and no headers.
Ok thank you from what I’m understanding I’m still going to be way over loaded with the two by 12’s on each side with 8’ centers on my posts, which really ends up spanning around 7’6” between the posts? Would that 3rd 2x12 underneath the inside 2x12 make much of a difference? I am also thinkin of possibly running something from the concrete pier to underneath the 2x 12’s so it’s bearing on something solid. Also every 4th truss is bearing on the post directly.
Viper98912
Well-known member
Wow, that's pretty gutsy to build such a large and tall shop with no engineered plans! And wow that is a lot of trusses!
edit:
If I understand your post correctly, the only thing that's holding up the entire roof between the 8' columns are a few ring shank nails? (nails that go through the 2x12's, face mounted on your columns?)
Nonetheless, given that you are in a snow area, and I don't know what the winds are like where you live, but I'd be concerned about the whole darn thing honestly. Do you have any local engineers that would be willing to do calculations for you? (you'd have to pay them of course)
I mean, it's possible you would've needed some type of LVL all the way around, sitting on the columns. You may need some major reconstruction here to beef it up.
edit:
If I understand your post correctly, the only thing that's holding up the entire roof between the 8' columns are a few ring shank nails? (nails that go through the 2x12's, face mounted on your columns?)
Nonetheless, given that you are in a snow area, and I don't know what the winds are like where you live, but I'd be concerned about the whole darn thing honestly. Do you have any local engineers that would be willing to do calculations for you? (you'd have to pay them of course)
I mean, it's possible you would've needed some type of LVL all the way around, sitting on the columns. You may need some major reconstruction here to beef it up.
jack stand
Well-known member
Run one of these under your inside 2x12 full perimeter* and fasten with 6" GRK RSS or Simpson equivalent. You should be able to use 8-10 per post with your 4 ply posts without overdoing it.
Then for additional support and actual bearing, run a 2x6 (or 2x8) vertically on the face of the posts supporting thi new beam down to the post foundation. Your pole barn nails will be fine but the above mentioned structural screws are much easier.
That image is from Boise Cascades site. LVL = laminated veneer lumber.
Your beam construction is very common with smaller "pole barns", your huge roof is the deal breaker and direct bearing coupled with a more substantial beam is called for.
This looks like a very nice building and you've done a nice job so far, except.... These LVL's are available in the 50' range. Use the longest length that you can safely get up there. A fastener in the last few inches of a board isn't the same as a foot away. Eliminating joints in this situation is a good practice.
*not necessary for the gable ends
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billconner
Well-known member
It would require engineering, but wonder if diagonals - center of headers to 4' down posts - would solve it. 4x6s or 6x6s with structural screws. The connection to post bring critical but something could be designed. Thought it might be an easier retrofit then long LVLs.
48” on center are you talking would have worked for the trusses of 48” centers for the posts
jack stand
Well-known member
I thought about this Bill and having the exterior sheathed attaching the outside of the beam to an added diagonal would be tricky but not impossible. Then unless you were able to drill approximately 18" through the diagonal-post-diagonal and through bolt it with some substantial all thread through all 3 parts at least twice per post it's again all down to the shear value of the fasteners.
If it were my building with this situation I'd use your approach with some miscellaneous 3x3x3/8 angle iron supporting the existing beams @ each post with through bolts simply to avoid the expense of all that lvl's.
Hoisting a 18" deep long lvl 16' up could be done safely with a couple of comealongs hung from a 4x4 that passed over 3-4 trusses being so close to the wall and 8.1 pounds per ft of weight. (1 3/4" × 18")
A day job for a couple of well rounded framing carpenters.
billconner
Well-known member
I figured some steel plates ar post, but leave that to engineer. I wondered if the brace could be mortised in an inch.
As far as top, does it need to be anchored to both 2x12s? Would a cleat attached to brace be enough under outside 2x12?
I saw the diagonals as an option one person could do alone with basic carpentry skills and tools.
As far as top, does it need to be anchored to both 2x12s? Would a cleat attached to brace be enough under outside 2x12?
I saw the diagonals as an option one person could do alone with basic carpentry skills and tools.
Firebrick43
Well-known member
The building is sheathed with osb. If its fastened according to the nail schedule it performs as if or better than you put diagonal members in.
The sheathing will support and stiffen the wall more than adding larger headers or diagonals.
And he used pole barn spikes to put the headers up, they are not just a "few ring shank nails". They are much more substantial than standard framing sinkers and pole barns all over the country typically have one truss setting midpoint on the header beam (4' truss spacing/8' pole spacing). 2' spacing is better as part of the load is closer to the poles than at one point only mid span.
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Fav Onefour
Well-known member
The framing is a whole lot better than most of the stuff around our area. Granted, we are not high snow load regs, but we get heavy snow loads with cornice drifting. Machine sheds are generally 60'+ wide with 8' truss spacing.
This is pretty common.
That doesn't make it right for your build, but it might help ease some concerns.
I'm sure the gang could have fun with the math and start figuring out the pole spacing across the end.
Trusses sit in post notches. (You have done that).
I think the biggest hangup with the comments is about the long 2X12 span with so many rafters supported by that component. It will probably be fine. Could it be better? Yes. For added comfort, add the additional interior header. That amount of support will get you past any concerns.
One thing I'd add, put in soffit venting while you're set up for all this work in the air. It sounds like this will be a shop. I'd assume it will be insulated. We even do venting in sheds like the picture above. The soffits are open mesh and the building does a lot of breathing. It is essentially shade instead of being a hot box.
This is pretty common.
That doesn't make it right for your build, but it might help ease some concerns.
I'm sure the gang could have fun with the math and start figuring out the pole spacing across the end.
Trusses sit in post notches. (You have done that).I think the biggest hangup with the comments is about the long 2X12 span with so many rafters supported by that component. It will probably be fine. Could it be better? Yes. For added comfort, add the additional interior header. That amount of support will get you past any concerns.
One thing I'd add, put in soffit venting while you're set up for all this work in the air. It sounds like this will be a shop. I'd assume it will be insulated. We even do venting in sheds like the picture above. The soffits are open mesh and the building does a lot of breathing. It is essentially shade instead of being a hot box.
jack stand
Well-known member
I've driven 100's of pounds of pole barn nails, I like the Maze brand.
I've been favoring....
and more recently....
they're a little more affordable in the bigger quantities.
The point of the added diagonals is to transfer a portion of the roof load to the post from near the midpoint of the span of the marginally sized "beam". Yes the building is "racked" nicely with the sheathing. Typical sheathing and nails will not assist much with this load path as their would be 1- 1/2" separation between the sheathing and the new diagonal.
My big concerns are the only 3" of available fastening* on the very end of the 2x12's and the lack of direct bearing and lastly the very light beam itself.
*I can see the lumber failing before the fasteners actually shear or deform. This is where a large timber or multiple ply's AND direct, correct 3" minimum bearing points come into play.
billconner
Well-known member
I cannot. I studied structures in grad school but not an engineer. The double 2x12s seem very under designed but as noted, I'm not an engineer. So not worth much from me but no, I do not believe the spacing makes a difference. That you're supporting about 3/4 of the roof load spread out between posts versus 1/2 at center makes little difference based on my education.
Viper98912
Well-known member
(Not a structural engineer, just giving my opinion)
Where you went wrong is that 3/4 of your load is supported by virtually nothing; only 1 out of 4 trusses is sitting on a post. Everything else is sitting on the 2x12's, where those 2x12's are face nailed to the posts. So the only thing really holding up 3/4 of that load are the shear strength of some nails.
Now, the statement above is grossly over-simplified. Because you may be able to calculate that you only need trusses every 8 feet and you'd be fine (good thing), and/or that the extra trusses are actually adding MORE load to your posts than actually helping (bad thing), etc. This also doesn't account for the fact that you have driven nails right at the edge of the 2x12's on some of the posts. Things could go either way without doing real calculations.
I'd say at a minimum I'd go ahead and add in a 2x running from the concrete pier up to the 2x12. Perhaps also consider running a 2x or 4x diagonal from the pier up to the center of the 2x12 (so, the 4' point between posts), to try to distribute some of the load from the center of the 2x12 down to the piers. I don't know how much this will help, but you really need to get much more load directly sitting onto the piers and not by the shear of the nail diameters.
Where you went wrong is that 3/4 of your load is supported by virtually nothing; only 1 out of 4 trusses is sitting on a post. Everything else is sitting on the 2x12's, where those 2x12's are face nailed to the posts. So the only thing really holding up 3/4 of that load are the shear strength of some nails.
Now, the statement above is grossly over-simplified. Because you may be able to calculate that you only need trusses every 8 feet and you'd be fine (good thing), and/or that the extra trusses are actually adding MORE load to your posts than actually helping (bad thing), etc. This also doesn't account for the fact that you have driven nails right at the edge of the 2x12's on some of the posts. Things could go either way without doing real calculations.
I'd say at a minimum I'd go ahead and add in a 2x running from the concrete pier up to the 2x12. Perhaps also consider running a 2x or 4x diagonal from the pier up to the center of the 2x12 (so, the 4' point between posts), to try to distribute some of the load from the center of the 2x12 down to the piers. I don't know how much this will help, but you really need to get much more load directly sitting onto the piers and not by the shear of the nail diameters.
Firebrick43
Well-known member
It is common to set a truss mid span on 8' OC post with 4' on center trusses. Common as dirt. Setting trusses on 2' is better as the load is more evenly distributed instead of right in the middle of the span.
Have you looked at many pole barns and how they are built? Some do notch the post, most however do not. Around here the only notched post is barns that get bookshelf girts.
2x12 header boards nailed with pole barn spikes to the outside and inside of the post is common as dirt as well. My barn is done that way and dozens of others around are as well. Do a google image search. And if one wanted to put a jack under the header, it sure as hell wouldn't need to go to all the way to the piers?
Give me a break. Sheathing applied to the face of the girts gives and is applied with proper 6" spacing on the perimeter and 12" on the interior will assist significantly in diagonal load paths from the header to the poles via the girts. Its more effective than diagonal bracing which why its become more and more common even though it cost more for super sized pole buildings to deal with the wind loads on the prairie here. Much larger buildings than the op is building.
2x12 is not light. Two 2x12 certainly is not. You may build different, OK, but the majority of pole buildings that are 48' wide used an inner and outer 2x12 header nailed on with pole barn spikes to the post without a notch to set in.
manwithtools
ALLIANCE MEMBER
It is common to set a truss mid span on 8' OC post with 4' on center trusses. Common as dirt. Setting trusses on 2' is better as the load is more evenly distributed instead of right in the middle of the span.
Have you looked at many pole barns and how they are built? Some do notch the post, most however do not. Around here the only notched post is barns that get bookshelf girts.
2x12 header boards nailed with pole barn spikes to the outside and inside of the post is common as dirt as well. My barn is done that way and dozens of others around are as well. Do a google image search. And if one wanted to put a jack under the header, it sure as hell wouldn't need to go to all the way to the piers?
Give me a break. Sheathing applied to the face of the girts gives and is applied with proper 6" spacing on the perimeter and 12" on the interior will assist significantly in diagonal load paths from the header to the poles via the girts. Its more effective than diagonal bracing which why its become more and more common even though it cost more for super sized pole buildings to deal with the wind loads on the prairie here. Much larger buildings than the op is building.
2x12 is not light. Two 2x12 certainly is not. You may build different, OK, but the majority of pole buildings that are 48' wide used an inner and outer 2x12 header nailed on with pole barn spikes to the post without a notch to set in.
100% spot on! Pole and post type buildings have been built that way for eons. Very rare to mortice in the headers. Face nailed 2x's are very standard. My newly built shop is exactly that way as are countless others. The companies that build these structure's literally have hundreds if not thousands of examples to rely on for proof this method works.
The other thing that is widely overlooked is that the external sheet metal diaphragm adds considerable resistance to shear and the engineers take that into account in these building designs.
Viper98912
Well-known member
It is common to set a truss mid span on 8' OC post with 4' on center trusses. Common as dirt. Setting trusses on 2' is better as the load is more evenly distributed instead of right in the middle of the span.
Have you looked at many pole barns and how they are built? Some do notch the post, most however do not. Around here the only notched post is barns that get bookshelf girts.
2x12 header boards nailed with pole barn spikes to the outside and inside of the post is common as dirt as well. My barn is done that way and dozens of others around are as well. Do a google image search. And if one wanted to put a jack under the header, it sure as hell wouldn't need to go to all the way to the piers?
All these can be common as dirt and you can find anything on google or tiktok or whatever the latest fad is. I just know that I wouldn't build myself a fairly large 72x48 building 16 feet in the air in a snow climate zone, without having someone run some type of math. Be confident all you want, I'm just providing my feedback as to what I would do in this scenario, since the OP is asking for suggestions. From a guy on the internet to another guy on the internet.
Remember, civil/structural engineering is a field where you're only allowed to build things once. This is unlike mechanical engineering where you can test, break, and build it better. If a structure falls down, it can cost lives.
manwithtools
ALLIANCE MEMBER
Do you realize that all the buildings "we" have referred to have been fully engineered?
They are not hip shots, they have engineered stamps in most all instances.
Firebrick43
Well-known member
My grandfathers 48’x96’x15’ has been up since 1976 and is doing just fine. My dad has the farm now and we are up here for thanksgiving dinner.
Walked out and the header is face nailed. As is most pole barns around here. In a snow zone and high wind zone.
It’s not as you are try to gaslight us saying it’s some “internet TikTok fad”
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billconner
Well-known member
Even the OP's?