Engineering question

Tacoma747

Tacoma747

Well-Known Member
Joined
Mar 20, 2005
Location
Winston-Salem
So I am no engineer, and this will not be permitted so it doesn't really need to be engineered, but I am putting two 40' containers at my land with a roof over the top of them. I found some 2' tall 48' long steel trusses. For you guys that might be structural engineers, does this look like it would be sufficient? I will have to weld pockets for the purlins to the tops of the trusses, that or attach the roofing metal horizontally and don't have purlins, but that obviously makes rain/snow not come off as easily. The drawing is obviously not to scale, but the upper container will likely sit 5+ feet higher than the bottom container. The span between the containers will be 28-30 feet, and I am hoping to do a clear span. The containers will be anchored to 2'x2'x6' concrete blocks at each corner. They are 40' containers and I can get 6 trusses, so they would be spaced every 8ft.

Thanks for any advice.

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I'm no structural engineer, but I'd run em like that all day long. I was considering something similar for a shed with some 53ft trusses I saw the other day. Ideally your truss supports should hit where the diagonal braces meet the bottom so you aren't point loading that unsupported area. You've shortened the total span so much that most of the engineery stuff doesn't matter.
 
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How many trusses do you have? I'd think you'd need 8 or 10 if you were going to have them close enough to screw the metal roofing to. I'd go with perlins. I have a cheap carport shelter with the roof run horizontal and it holds leaves and pine straw like nobody's business.
 
Tacoma747 said:
Good point. With 8ft between trusses that wouldn't be close enough to run horizontal roof. Purlins it is.

Anyone know a good source or idea for attaching the purlins? I guess I am going to have to get a cheap 120v welder and take a generator up there to do the welding.
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Purlins are usually bolted to steel with 1/2” bolts and purlins spaced no more than about 6’ OC. 8’ between trusses is likely way too much span for the metal, especially if it happens to be 29 ga. Someone is going to have to climb up there and screw the panels down. 8’ span on the decking won’t support someone up there screwing them down.
 
braxton357 said:
How cheap are the trusses? You might save yourself a lot of headache by buying some already built for this
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Going to try to get all 6 for $3k. But I know he will take $3600. I am going to call R&R and see what they say but I figure they will be considerably more.
 
rockcity said:
Purlins are usually bolted to steel with 1/2” bolts and purlins spaced no more than about 6’ OC.
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Yea, but how do a bolt a purlin standing vertically to a truss? I know you can lay purlins down but I wouldn't think that would be a good idea with them having to span 8'. I figure I will have to bend a bunch of the little u-shaped pockets and weld them on the tops of the trusses, unless there is another way to go about it.
 
Tacoma747 said:
Yea, but how do a bolt a purlin standing vertically to a truss? I know you can lay purlins down but I wouldn't think that would be a good idea with them having to span 8'. I figure I will have to bend a bunch of the little u-shaped pockets and weld them on the tops of the trusses, unless there is another way to go about it.
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Maybe buy some kind of joist hangers from LowesDepot? Would save the trouble of making them at least.
 
Tacoma747 said:
Yea, but how do a bolt a purlin standing vertically to a truss? I know you can lay purlins down but I wouldn't think that would be a good idea with them having to span 8'. I figure I will have to bend a bunch of the little u-shaped pockets and weld them on the tops of the trusses, unless there is another way to go about it.
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There is zero chance I’d try to stand purlins vertically to use them. You marching for error screwing that down is near zero.
If the span is too wide I’d switch to 2x befor I’d try to stand up 1x dimensional
 
Tacoma747 said:
Yea, but how do a bolt a purlin standing vertically to a truss? I know you can lay purlins down but I wouldn't think that would be a good idea with them having to span 8'. I figure I will have to bend a bunch of the little u-shaped pockets and weld them on the tops of the trusses, unless there is another way to go about it.
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What material are your purlins?

There are hundreds of ways to attach a purlin to a truss, metal to metal, wood to wood, wood to metal…

I mean, it’s not that difficult. Simple angle iron would suffice or there are specialty clips if you want to get fancy.

Purlins work better standing up vertical. Install them vertical. And yeah, purlins should be at least 2x material or metal. Use a chalk line to avoid missing the purlin with the screws.
 
Ron said:
There is zero chance I’d try to stand purlins vertically to use them. You marching for error screwing that down is near zero.
If the span is too wide I’d switch to 2x befor I’d try to stand up 1x dimensional
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That's how they are commonly done with steel trusses.
 
Alright I’ll shut it up now. I’m obviously no carpenter …and I didn’t use 1x6s for purlins for my recent tin roof project…. Nope sure didn’t
 
On my Morton shop the wood trusses are on 8' centers. Then the 2x4 purlins are set vertically on the truss and they hand drive a 60 penny nail through that into the truss. Then screw metal roofing to the 2x's. Their purlins come with a metal bracket on the end to butt the next purlin to it flush then short screws in the bracket. Not sure how wide your metal trusses are but maybe you could break the 2xs on them and nail a short 2x across the butt joint.
 
Ron said:
Alright I’ll shut it up now. I’m obviously no carpenter …and I didn’t use 1x6s for purlins for my recent tin roof project…. Nope sure didn’t
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For bullshit deer stands and such I'll slap some 5/4 deck boards up there in a minute for purlins.
 
rockcity said:
What material are your purlins?

There are hundreds of ways to attach a purlin to a truss, metal to metal, wood to wood, wood to metal…

I mean, it’s not that difficult. Simple angle iron would suffice or there are specialty clips if you want to get fancy.

Purlins work better standing up vertical. Install them vertical. And yeah, purlins should be at least 2x material or metal. Use a chalk line to avoid missing the purlin with the screws.
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I'd be using 2x6's. I am going to run by DH Griffith and have a look around to see if they have anything useable. I had just envisioned the purlin mounts like used on steel pole barn trusses, but I guess cutting some angle iron and welding it on would be simple enough. I would definitely install them vertically.

I guess if I could find a bunch of cheap tubing at DH Griffith maybe I could do purlins out of metal and just weld them (or bolt them) to the trusses. But I can't imagine being able to find that much tubing that is in good enough condition.
 
Yeah, the easier thing to assemble would be long legged channel or square/rect tubing, but that may still be a pain because you will have to pilot drill the holes through the roof and the purlin.
 
Call r&r they have built trusses for connex boxe garages before, you'd only need 4 and you wouldn't have to put one of the containers up in the air. Can also get the purlin 2x6s and roof metal from them cheaper than you going to find anywhere else.

If you decide to diy let me know I'll get you some purlin cups.
 
You can borrow my portable 110 welder if you need to. It's a heavy basterd but works well. It's a Hobart 140. If you ended up needing it.
Cool project!
 
You can buy metal purlins from a local building supplier here btw, they're not terribly expensive, come in 21ft length
 
braxton357 said:
Call r&r they have built trusses for connex boxe garages before, you'd only need 4 and you wouldn't have to put one of the containers up in the air. Can also get the purlin 2x6s and roof metal from them cheaper than you going to find anywhere else.

If you decide to diy let me know I'll get you some purlin cups.
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The container isn't really up in the air. It is just uphill from the lower one. But using the blocks to raise it up some so that the dozer and excavator actually have a chance of fitting under the roof and to give it a foundation to anchor it down to.
 
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