Best Way To Span 32', Unsupported

 
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Old 11-12-2017, 09:53 PM   #1
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Best Way To Span 32', Unsupported


Hi y'all. First time poster. Thank you in advance for any responses to this.

Customer wants a 30'x50' open-bay Lean-To style carport. Not enclosed. He wants 6x6 supports around the perimeter of the building only. Completely open inside. No supports in the interior. Vertical suports will be 6'x6'x15' on the low side and 6'x6'x20' on the high to achieve a 2/12 roof pitch (this is in order to match his existing garage roofline - which this new carport will butt up against.) See pics.

Since its not an enclosed structure I'm thinking pressure treated Glulam LVL beams to span the 32' is my only option. Could use some help knowing if
1) This true or if there are other ways to do it that would be better &/or more economical (Metal construction isn't an option).
2) What LVL size beams would I use to handle worst case scenario snow load
3) How many LVL beams would I need to properly support the 32'x52' roof (1' overhang around 30x50 foundation)?

I will be getting drawings, engineering stamp, permits on this but want to approach them with most of it solved already to minimize the engineering on their end.

WRT the attachments. I just did a quick concept sketch in google sketchup to see if I was in the right ballpark with the customer on what he wanted. It's in no way a finished product. I put in 2x12x30 Glulam LVL's at 12" OC as just a place holder till I know what actually should go there.

Thanks again.
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Best way to span 32', unsupported-screen-shot-2017-11-11-11.11.11-am.png   Best way to span 32', unsupported-screen-shot-2017-11-11-11.12.04-am.png   Best way to span 32', unsupported-screen-shot-2017-11-11-11.19.38-am.png   Best way to span 32', unsupported-screen-shot-2017-11-11-11.20.49-am.png  

Last edited by Swabbie; 11-12-2017 at 09:57 PM.
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Old 11-12-2017, 10:10 PM   #2
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Re: Best Way To Span 32', Unsupported


Hi, just about impossible to answer without knowing snowloads, windloads etc. But...
What you are proposing will not work.
1. 6x6 will be to small
2. Lvl are not the same as glulam

If you are trying to stay as close to your design. You will want to embed proper size posts a certain depth into ground using sonotube and fill with concrete. Post every 12.5’(again will have to be determined)
Glulam beam running parallel to long distance spanning posts. Prob end up being 6” wide 14” deep.(tbd)
Then some top hung trusses spanning the 30’. C/w 2x4 purlins and metal roof.
Post will need proper bracing as well.

Something like that


Few more things, I shouldn’t just say 6x6 will be to small but I think they would. For the front you will need a 25’ 6x6 or something like that. If trying to stay wood, glulam posts are prob a better choice, also you prob could sub glulam rafters instead of trusses but it will be getting expensive at this point. Not to be rude but this whole exercise is kinda pointless without knowing local codes and loadings

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Old 11-12-2017, 10:17 PM   #3
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Re: Best Way To Span 32', Unsupported


Steel framing.

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Old 11-12-2017, 11:22 PM   #4
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Re: Best Way To Span 32', Unsupported


2X4s
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Old 11-13-2017, 07:01 AM   #5
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Re: Best Way To Span 32', Unsupported


Mono truss, unless you need the ceiling sloped.
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Old 11-13-2017, 08:05 AM   #6
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Old 11-13-2017, 08:06 AM   #7
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Quote:
Originally Posted by B.Johnson View Post
Mono truss, unless you need the ceiling sloped.
He does want the ceiling sloped/vaulted.
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Old 11-13-2017, 08:07 AM   #8
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Quote:
Originally Posted by MeanWeen View Post
Hi, just about impossible to answer without knowing snowloads, windloads etc. But...
What you are proposing will not work.
1. 6x6 will be to small
2. Lvl are not the same as glulam

If you are trying to stay as close to your design. You will want to embed proper size posts a certain depth into ground using sonotube and fill with concrete. Post every 12.5’(again will have to be determined)
Glulam beam running parallel to long distance spanning posts. Prob end up being 6” wide 14” deep.(tbd)
Then some top hung trusses spanning the 30’. C/w 2x4 purlins and metal roof.
Post will need proper bracing as well.

Something like that


Few more things, I shouldn’t just say 6x6 will be to small but I think they would. For the front you will need a 25’ 6x6 or something like that. If trying to stay wood, glulam posts are prob a better choice, also you prob could sub glulam rafters instead of trusses but it will be getting expensive at this point. Not to be rude but this whole exercise is kinda pointless without knowing local codes and loadings
Good Point. Forgot to mention the location. Anne Arundel County, MD. Looks like 25psf for Snow Load and between 90 and 125 Vmph for Wind load depending on what Category this building would fall under (No idea).

Knowing this, what are your thoughts now?

Reference:

http://dhcd.maryland.gov/Codes/Docum...01,%202012.pdf
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Old 11-13-2017, 08:11 AM   #9
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Re: Best Way To Span 32', Unsupported


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Originally Posted by WarnerConstInc. View Post
Steel framing.

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No really an option only because I have never worked with it. For academics, what would you specify for supports and beams to make this work in steel? Whats a good source to buy such materials. Project is in Maryland.
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Old 11-13-2017, 09:48 AM   #10
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Re: Best Way To Span 32', Unsupported


Damn hoss.

I'm all for helping folk out on here, and those who know me, know I've done my fair share, but sometimes, when a newb comes here, has never posted anything, and then wants complete design help, from scratch, I don't know what to say.

I'll say this, if you, as the Contractor, need this much help right from the start, and can't find it on your own, you might want to pass on this job.

But, in an effort to help you, this is how you should go about finding the info:

If you want to look into steel, call some local supply houses, and/or fabricators. I live 3,000 miles from you, I'm not gonna research steel sources for you. Then, talk to them about span.

Look into trusses. Call your local truss outfit, and get a price on trusses to span that much. I'm currently doing one that spans 42 feet, no supports. It's just not that hard.

Call your lumber yard, and get a price and specs on Glulam, LVLs, built-up beams, solid-sawn lumber, whatever. Learn the differences between them. Your lumber yard or the interweb can help you.

I'm happy to help in any way I can, but if gotta design, plan, and price, the whole thing for ya, I'm gonna bid it, too. I'll sub it out to ya.




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Old 11-13-2017, 10:01 AM   #11
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Re: Best Way To Span 32', Unsupported


Quote:
Originally Posted by Swabbie View Post
I will be getting drawings, engineering stamp, permits on this
Which is what any of us would do.

Quote:
but want to approach them with most of it solved already to minimize the engineering on their end.
Oh c'mon. Cut the crap. "minimize the engineering" translates into "how can I save money?"


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Old 11-13-2017, 11:01 AM   #12
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Re: Best Way To Span 32', Unsupported


All you need is a general idea and measured concept drawing, and the engineer will do the rest. It doesn't save you much to work out the structural details.

I agree with a previous poster, with no bracing, you'll have to sink the posts.
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Old 11-13-2017, 12:05 PM   #13
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Re: Best Way To Span 32', Unsupported


Another advantage to ballpark engineering this (aside from my guy charging me less if it's mostly worked out) is I can work up a ball park materials estimate for the customer to then see if I am in his ballpark budget THEN we will pay to have it actually engineered. Standard practice from where I stand. As others have said, its not that hard. Thanks to those who helped me see there are components to this that I hadn't thought of.

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Old 11-13-2017, 12:44 PM   #14
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Re: Best Way To Span 32', Unsupported


First, I think you have to get your terms in the right ballpark.

WTF is a Glulam LVL?

The "beams" as you call them are roof joists.

"Vertical suports", aside from the spelling, I will give you, except to say we generally refer to them as posts.

You will not save any money trying to do the engineer's work for him. It doesn't work that way.

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Old 11-13-2017, 01:21 PM   #15
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Re: Best Way To Span 32', Unsupported


You really need to ask this customer where he or she got the idea for this structure. Can he or she tell you where something like this can be seen already built, in the area?

A quick check with Weyerhaeuser's free Forte application shows that their 210 series TJI joists might work at the 16" depth, and at a spacing of 32".

This solution was gotten using a snow load of 25 psf and wind load of 20, live load at 12 and dead at 10.
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Old 11-13-2017, 02:05 PM   #16
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Re: Best Way To Span 32', Unsupported


Quote:
Originally Posted by Swabbie View Post
Another advantage to ballpark engineering this (aside from my guy charging me less if it's mostly worked out) is I can work up a ball park materials estimate for the customer to then see if I am in his ballpark budget THEN we will pay to have it actually engineered. Standard practice from where I stand. As others have said, its not that hard. Thanks to those who helped me see there are components to this that I hadn't thought of.
Actually, this is, in fact, that hard. Sizing girders and engineered rafters can be done by the supplier, no big deal. The posts and footings if unbraced aren't, and connections can be tricky.

Unless you think your time monkeying around with this has no value, go to a steel structure manufacturer and have them quote fabbed materials for the whole project.
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Old 11-13-2017, 03:25 PM   #17
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Re: Best Way To Span 32', Unsupported


Quote:
Originally Posted by Willin View Post
You really need to ask this customer where he or she got the idea for this structure. Can he or she tell you where something like this can be seen already built, in the area?

A quick check with Weyerhaeuser's free Forte application shows that their 210 series TJI joists might work at the 16" depth, and at a spacing of 32".

This solution was gotten using a snow load of 25 psf and wind load of 20, live load at 12 and dead at 10.
Thank you for the input. I haven't found where they make these for exterior application though.
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Old 11-13-2017, 04:31 PM   #18
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Re: Best Way To Span 32', Unsupported


Then go 14" LVL on 16" centers. But an LVL isn't really OK unless you can build so it will always be dry.

If your client wants a wood framed structure with the rafters all exposed, he or she really owes you some info. Where was this seen? In what universe does a 30' clearspan woodframed carport structure exist with 25 psf ground snow loads?

For this to get built and survive, it will need some structural design for the frame (not the roofdeck structure) so as to have all the proper moment resistance.

Good luck.
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Old 11-13-2017, 06:49 PM   #19
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Re: Best Way To Span 32', Unsupported


The customer needs to have this engineered, then give you the plans to bid. You're going about this backwards, probably in the hopes that it will help you get the job, but it is most likely going to get you in a bad situation. I have no problem saying "see an architect/engineer, and then come to me for pricing."
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Old 11-13-2017, 08:26 PM   #20
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Re: Best Way To Span 32', Unsupported


Design Build Contract...


Customer pays you X. For that price you get an engineered drawing done and provide a quote to build from that.

This way you get paid to quote it, the drawing gets paid for, and the customer feels committed to you due to the idea of a sunk cost.


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