Fasteners per pole barn header, am I thinking about this right?

[petebert]

Menards 24x50 pole barn. They include a box a 60d 6" nails and don't tell you how many you need to use. I'm wanting to use Spax construction lags instead of the nails.

So here's my thinking, 25lb snow load, 10lb dead weight, add in a buffer, so lets say 40lbs x 24 x 50 = 48000lbs of potential weight on the headers.

There's a north and south wall, so each wall will hold 24,000lbs. One header on each side of the posts, so 12,000 per side and there's a post every 10' so 2400lbs per 10' section. So is this the correct way to think of this, are the fasteners for each 10' section responsible for 2400lbs of weight?

Now I look at the Spax specs, 250lbs/in for the 5/16 screws and they include this note "Withdrawal” design values are to be multiplied by the length of the thread penetration into the side grain of the main member. Length includes tip." So I believe this means if I got a 6" screw, subtract 1.5 for the header thickness, that leaves you with 4.5 x 250 for 1125lbs per screw. So 2 screws per post would give me 4500lbs per 10' section.

 

[dougtrr2]

My head is spinning from the math. But, aren't those screws going to be in shear mode rather than withdrawal mode?

Doug in SW IA

 

[EddieWalker]

...

There's a north and south wall, so each wall will hold 24,000lbs. One header on each side of the posts, so 12,000 per side and there's a post every 10' so 2400lbs per 10' section. So is this the correct way to think of this, are the fasteners for each 10' section responsible for 2400lbs of weight?

...

Are you going to attach the headers to the sides of your posts with a fastener? Either the 6 inch nails that came with the kit, or structural screws that you will buy?

In my experience, you never want the load of a header held in place by a fastener of any kind.

For maximum strength, the ends of the header should be resting on solid wood. In home construction, the header is supported by a Jack Stud. In pole barn's, you can attach blocking to the sides of your posts to create support for your header, or you can notch the top of the post for one of the headers, and block the outside header.

I would use structural screws to hold the header in place once it's supported by lumber under it.

 

[KennyG]

Eddie has it right, as usual. The headers should be on notches or plates. Your math may work but you are thinking of it wrong. Bolts, screws, nails don't provide the shear resistance. They hold pieces together tightly so the friction between the pieces provide the shear force.

 

[kinglake]

I've been in hundreds of pole barns and never seen one with the poles notched for the headers. Not saying its a bad idea, just unneeded.

 

[kinglake]

As a follow-up, look at Morton Building, maybe the largest pole barn builder, whom doesn't notch. RR Buildings on YT, while not technically pole barns, doesn't notch either. It simply is not required or needed.

Same scenario for decks, poles should not be notched.

 

[EddieWalker]

Notching is just one option that is very effective at providing the most strength possible. Morton likes to use laminate posts in their buildings, and they provide more of a Jack Stud when fabricating their posts so the header has solid wood under it.

Another option, which is very common in decks, is to put the header on top of the post. One of the biggest mistake people make with decks is not understanding the difference between a "beam" and a "joist" The next biggest mistake is relying on nails to hold their "beams" in position.

You also have to identify if the lumber is actually supporting a load. If it has a truss resting anywhere in the span, between the posts, then you need a header that is supported by solid wood under it. If the truss is resting on the post, and there isn't anything on the span of the top board, then you have a purlin, and there isn't any need to do anything more for strength.

When building, never rely on what others do, or we've always done it this way, or what somebody got away with. Always build using best known methods.

 

[JJT]

As a timber framer I'd go the extra mile and notch the post on a pole barn.

Every single joist/beam/girt I cut goes into a housed mortise joint. Otherwise the strength of the timber is limited to the strength of the tenon, or in the case of a non notched post in a pole barn, the strength of the fasteners.

 

[EddieWalker]

That's really nice. It's pretty fast and simple to notch posts, but I've never done a mortise joint before.

 

[kinglake]

When building, never rely on what others do, or we've always done it this way, or what somebody got away with. Always build using best known methods.

I am not arguing, but Morton buildings are well engineered. If you want to go overboard, go for it, but it is unneeded and a waste of material. "Best known method" is comprised of many things, including the most efficient way to accomplish the goal.

*Morton does use laminated poles, but the laminations are parallel to the trusses. There is nothing under the ledger board unless it is required for siding in which case it is not structural.