pole barn designing 40x64ish

[KennyG]

I would side with Eddie on the built up 2x12s and plywood. Make it the same thickness as the posts. I'm skeptical of wood box beams. Metal box beams work because they are one continuous material. Built up laminated timbers beams work because, even if they aren't glued (which they should be) they all act in the same loading. A wood box beam has different forces acting on the mating pieces and that would worry me. I'm not saying it's not a way to build a strong beam, I'm just saying that if I tried to structurally analyze it I would have to worry a lot about load transfer between the members.

The idea of stacking 2x12s has some merit,but I don't think you need it. 3 2x12s with plywood should be plenty to span 16 feet. If you did stack them, I would want continuous plywood sheets tying them together.

If the Amish are using boxed headers (I haven't seen this) I would guess it's to save material. Headers in house construction are often way over designed.

Anyway, these are thoughts off the top of my head without any detailed evaluation, but when we see "everyone always does it this way" there is often a reason.

 

[bigtiller]

How about making the laminated 2x6 posts on each side if the door a little bigger. 3 Laminated 2x8's would give you room for the forth 2x12 in the header you are talking about ?

 

[LD1]

The idea of stacking 2x12s has some merit,but I don't think you need it. 3 2x12s with plywood should be plenty to span 16 feet. If you did stack them, I would want continuous plywood sheets tying them together.

The idea behind stacking them was to avoid going with a a beam as wide as the posts. I dont want that. The top of the posts are going to be notched for the trusses. Dont want this setting on the beam, only 1 or maybe 2 plys can be notched in and leave room for that.

And since height is of no object here, Adding depth SHOULD do lots more good than width. 2 2x12's in this way I would think would be lots stronger than even 3 side by side + plywood.

As with steel, the most efficient use of material to gain strength is depth. The only time it would make sense to use a shallower but far heavier beam is if space is an issue.

How about making the laminated 2x6 posts on each side if the door a little bigger. 3 Laminated 2x8's would give you room for the forth 2x12 in the header you are talking about ?

Trying to find solutions to build a strong beam and save money. Certainly not wanting to go with a 4th 2x12. Those arent cheap.

 

[KennyG]

I'm having a little trouble envisioning your posts notched for trusses and how that impacts the beam. Will this 16 ft beam be outside the posts, like a wall girt? If so, it would be supported by 2x scabs on the posts. You could laminate inside the posts and would not need additional end support inside the posts. If you want to do the stacked 2x12s I think that should work but I would still put a wide (22-1/2"?) plywood lamination on the inside surface. The other thing to consider is how you will attach the truss at the center of this 16 foot span. With a beam only about 2" wide, the truss will want to twist the beam at this point. Are you going to have an inside girt at the top of the wall to also anchor the truss to? The stacked 2x12s should have plenty of vertical capacity, but there are also horizontal and torsional forces and 16 feet is a considerable span.

 

[LD1]

Here is the box idea I was proposing.

 

[TomSeller]

After five pole barns I can tell you to build bigger than you want..

Any chance of you posting pictures of them? It would be very much appreciated. Or if you did on a previous thread, any reference?

 

[franklin2]

I find all this different design ideas interesting. But do you really have the freedom to make it any way you would like? I built a very small 25x30 garage/shop, and I had to submit plans to the county and they had to be approved. They usually go straight down the middle with conventional building practices. Something like a steel beam spanning a large opening they would shy away from and say "it has to be engineered".

I had a line on a bunch of those tall steel rack legs they use in manufacturing warehouses. They are super strong and very tall also, and I thought I could dig a footer and let it sit above grade, and then take these rack legs and bolt them together all the way around to make the walls. Then put a wooden header around the top, sit the trusses on that, purlins on the sides, metal siding, etc. No way would they approve something weird like that where I live.

Like the laminated post debate. If they had never seen it before over here, it would probably be a resounding NO!

I figured Ohio might be the same way, buy maybe not?

 

[EddieWalker]

I do a lot of remodels and get to see how homes have evolved in building technique over the years. Some things surprise me and I wonder why they did it that way. While I've never seen a hollow box for a header to the scale you are describing, I have seen plenty of headers with lumber at the top and bottoms of them without plywood in between that left a half in void in the middle of the two vertical boards.

In my opinion, and what I know about building, plywood was very expensive and not readily available back then. To get the width of the header the same as the thickness of the studs, they just used a stud at the top and bottom of the header boards to keep them aligned. If the boards are of the proper size, this should work. In most cases it has, but one of the reasons I get hired to fix these things is that it doesn't always work.

Lumber over a span will sag over time. Bigger lumber sags less and it takes longer to happen. You size the lumber according to the span and when there is an additional load on the span, you double or triple up those boards. To make it even stronger, you add plywood between your boards. Plywood or OSB has tremendous sheer strength and it will not sag over time when on it's edge. This is why OSB is being used for I joist. The top and bottoms boards are just there to keep the OSB straight, but don't add much in the way of strength. All that strength in the Plywood or OSB is added to the strength of the lumber used in the header when they are all tightly fastened together.

Glue is stronger then the wood it attaches to. There was a great study that somebody linked to on hear awhile ago that showed that even the cheapest white elmers glue was stronger then all the woods they used in their test. For the cost of glue, it makes no sense not to use it. Especially for something that you are spending a lot of money to build and plan on having the rest of your life.

You can easily install your header on the top of your posts and still have plenty of room for your trusses. Tying them together on the top of the post will give you the maximum amount of strength possible. Then you just frame down from the header for the door opening to the door with cripple studs. Headers can be at any height in the wall.

Eddie

 

[chevy]

2 years ago, we had a 42' X 60' X 14' tall Lester pole barn built by a local builder.
The posts & trusses are spaced 10' on center, It has 2 - 10' X 10' & 2 - 9' X 9' overhead doors.
The posts are full length laminated 2 x 6s.
I built a 19' X 42' loft on one end. The lower ceiling height is 7', the upper ceiling height is 6' 2".
I also added a floor in the truss spaces above the loft floor for storage of light weight objects.
I have not had time to do any interior wiring yet, other then installing the main panels.
The only lights I have at this time are on 2 garage door openers.

 

[ultrarunner]

Nice building and very practical with the loft...