Pole barn engineering help needed...

[Joel Eisner]

Here is the background:

I am considered a residantial and have put up a 36x46 ft pole barn.  It is 6x6 pressure treated posts that are spaced a maximum of 12 ft o.c. along the eaves with 36 ft engineered trusses 24 ft o.c. It is a 4/12 roof and 27.5 psf load.  I have 2x10's doubled up along the eaves that are nailed and double lag bolted to each post.  The first run of 2x10's have their ends over a post but I set the second set up at the full 14 ft length so the ends do not always fall over a post.  Some of the posts did not go down a full 4 ft, but only 3 ft so the inspector asked for cross bracing.  For bracing I used double 2x6's at 45 deg as knee braces at the four corners (apposing) and at the two intermediate posts on the gable ends.  I also sheathed two eave side walls (24 ft long each) with 1/2 " osb and nailed and glued it.  I did the same thing to an interior wall that has 3 more 6x6 posts.





1. The inspector on the final did not like the second set of 2x10's not breaking over posts.  The problem with doing it like he wants it is that if they break over posts the breaks in the double 2x10's will line up with each other and could cause a scisor action.  He wants the longest span (11-8) and the breaking 2x10's not over posts engineered.

2. He wants the lateral bracing engineered.

Do these seem like reasonable requests?  I am hoping to discuss it since it is already seeming overbuilt for a pole barn and these things were not brought up on the intitial plan reveiw.  The problem is that most barns in my county are on farms and do not require permits or inspections so I think he is not used to this type of building.

Help.... anyone want to stamp this for me of give me some advice?

[Nate Surveyor]

Various words come to mind.  ??? ??? ???

When you have this much interference with your constitutional right to privacy, it is time to MOVE!

N

[beenthere]

Do you have a detail pic of the #1 concern of his?? re: 2x10's at ends.??

[Joel Eisner]

Do you have a detail pic of the #1 concern of his?? re: 2x10's at ends.??

Here is an example (view from the top).  One set of 2x10's break over the posts and the other set does not.

P = post    _______ = 2x10

________ ____________ __________ ___________
___________ ___________ __________ _________
P              P                       P                   P                   P

[beenthere]

I see now..thanks for the pictorial.
....what numbers did you use for the design you came up with...double 2x10's, on a 12' span supporting the ends of 36' truss.   If the numbers add up, and you can show them to the inspector (hopefully he can interpret them), should be able to fly with what you have. Does the inspector have numbers that contradict yours?

I'd at least go bolts, instead of lag bolts to hold up over time. Without crunching any numbers, I'd go at least three 2x10's glued, bolted, and the two outside laminations breaking over the posts, with two lams sitting on the post.  But that is just 'seat of my pants' feeling.    Seems the biggest enemy here is sagging from long term loading of the double 2x10's spanning the 12'..

[Don P]

Sheltering oneself or ones possessions is not a constitutional or even basic human right in this country  :-\.

He is "correct". Prescriptively you have to splice over a support, beyond that is "engineering required".
For the lateral bracing you can check against the truss prints and the codebook, I imagine that will get into engineering too.
Pole buildings are not prescriptive so he does have the right to ask for full engineering for the entire structure.

Inspectors would like prescriptive pole barn designs, so far the most resistance seems to be from engineers, go figure  :.

For decks our building dept solved the lap problem by requiring posts no more than 8' apart without engineering.

[Joel Eisner]

So I am waiting for a call back from the building dept.  We might be making progress.  Since we are not considered a farm he is applying residential code to the structure and the maximum eave opening (for my tractor) is 12 ft o.c. and with the building being 36 ft wide I need a top girt (or header if a stick built house) of quadruple 2x12's.  If that is the case then I think 99% of pole structures are going to fall down this winter during the first snow storm.   ???

[stonebroke]

Too bad you are not a farmer. We manage to get by with a lot of stuff. I would think down there you would not have much of a snow load . That is what brings barns down up here.

Stonebroke

[stonebroke]

Also we have no problem with having boards end at the pole we put one on one side and ther other on the inside. then put spacers in the middle and it is much stronger.

Stonebroke

[Thehardway]

Joel,

You may be able to console him and reach a compromise using pre-engineered metal fish plates, but then again he will proably say he needs the engineering documentation.  It is a categorical thing.  You saw it as a splice and designed it to overlap to avoid scissor action.  I feel your instincts are correct however it is technically regarded as a cantilevered beam unless supported at both ends and that throws him into "ask for engineering" mode because it falls outside the standard span tables.  The simplest solution to satisfy him is probably to jack the thing up 10" using your existing beam and some barn jacks, then build a three ply 2X10 beam to replace the existing with the two outside plys falling on the posts and the center ply continuos over the post with splice mid-span.  Through bolt it with some galv. bolts to the posts and nail the crap out of it along the distance of the beam from both sides.  Once it's in place you can let the roof trusses down and remove the old beam. If you can show him your calculated roof load and the span table for 2-2X10's supported at ends you should resolve the issue as well as satisfy your concerns over scissor action.

The bracing is another issue altogether and I'm not sure there are any work arounds.   The only thing I could tell you here is put some massively long X braces between your poles.  This should satisfy his needs for inspection. After he signs off you can temporarily remove the braces that are in your way.  Bracing is important on pole buildings no matter how deep your poles are buried.  It is not uncommon for something to happen to one of the poles (tractor gets away and takes out a pole, or wife backs into one with truck) and if it isn't well braced it will fall like dominos.  Don't ask me how I know ;D

Project is looking great!  Eisner and Sons Sawmill appears to be alomost ready for action. :D

[Joel Eisner]

Okay...  they called back and asked that I place one more 2x10 on the eave sides with the breaks over posts.  I also need to place blocks on the posts under the 2x10's for support and paint/stain or promise to paint/stain exposed wood.  

The 2x6 bracing needs 5/8" bolts and that should be good.  

I guess all of that is cheaper than an engineering consult.

[scsmith42]

Joel - So you'll end up with the equivalent of a 6 x 10 for a 12' span?  WOW  And people think that I build things "over kill"...  Let me know if you need to borrow a jack to raise the beams for inserting the blocks over the posts.  I've got a 20T air/hydraulic jack that makes this easy... well, easier than jacking by hand that is!

Don, I've got a technical question. To me, it seems that when laminating two boards together, you'll have a greater strength in the corresponding beam if you stagger the ends, versus having them meet up over the posts.

My thoughts are that by staggering the ends and making a beam, youll have a continuous unbroken line along the top and bottom of the beam for providing tensile strength in the beam.

If you have the ends meet up over the posts, wouldn't high loads on the spans cause a sag in-between the supports, which in turn would cause the beams open at the top over the posts?

Scott

[Joel Eisner]

Joel - So you'll end up with the equivalent of a 6 x 10 for a 12' span?  WOW  And people think that I build things "over kill"...  Let me know if you need to borrow a jack to raise the beams for inserting the blocks over the posts.  I've got a 20T air/hydraulic jack that makes this easy... well, easier than jacking by hand that is!

No jacking required.  I am going to glue and nail up another 2x10 on the inside and then place blocking under the 3 2x10's with bolts in the blocks and the 2x10's.

[beenthere]

..........
No jacking required.  I am going to glue and nail up another 2x10 on the inside and then place blocking under the 3 2x10's with bolts in the blocks and the 2x10's.

Good fix...easy to do, and gives the two-ply with ends over the posts, as well as the center ply which ties the joint together and gives the cantilever support. And, gets the monkey off your back....

[Don P]

That's what I was thinking after I left this morning, ignore the overhanging 2x10 and sister on whatever it takes to meet code. The overhanging 2x10 is just some good gravy at that point. I do like the idea of weaving the joint, just by code it is non bearing.

Scott, you have a point and we do typically stagger joints whenever possible in beams and girders. This typically requires 8' or less post spacing, that's the reason for that limitation in our deck code. Overhanging a piece of lumber and using it as part of the load bearing beam would mean that the connection be moment resisting. A splice at the inflection point of a non moment resisting joint is simply two overhanging beams that happen to meet. An engineer is qualified to make that call. In the field I try to follow the prescriptive methods. Nothing says you can't add an additional tie to weave things together with the required post to post beam.

We usually notch beams into posts. Going back to decks, we are not allowed to bear on bolts at the posts.

The inspector went out on a limb for you Joel. After making the initial call he should have stuck to his guns if he listens to the county attorney. Remember he is not judge and jury, just a cop stuck in the middle. Sometimes they can choose not to see a speeder but that is not a cops job. He stood in the breach and made a common sense call, definitely not his job and one that just bought him liability, he ain't all bad.

[Joel Eisner]

We are having our reinspection tomorrow.  We ended up placing a third set of 2x10's up with the ends over posts and bolted them and the braces up.  We also got nailed for not having the plumbing and elec trench inspected and the inspector originally wanted in dug u every 20 ft.  He ended up letting me write a note to file that was notarized saing that it is all at least 18 in deep.

I guess Santa came early

[krusty]

The Ontario Building Code has a section on pole barn construction available online. Since the only big difference is the heavier snow load here I would look at it for design guidelines. It should cover off the technical aspects of your design and then you can convince your inspector it is adequate.

Though noone likes to spend $$ on an engineer, some things are worth it, especially when a couple hundred $$ will ensure your structure does not fail.