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Sizing Built Up Deck Beams

 
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Old 09-06-2008, 07:55 AM   #1
 
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Sizing Built Up Deck Beams


I am looking to build a deck over a retention area on one of my company's properties- will be a smoking area. In order to save a few bucks I get to be the engineer on this one. The retention area is 22'8" by 90+' and 5' deep and constructed of 8-8-16 CMU dowelled with #5 and poured solid. I need to span the 22'8 with a 30' wide deck, ideally attaching ledgers to the CMU walls on 2 sides. Span tables say I can go 22'8" with 2x12 #1 SYP at 12"OC, but the lumber yards say no #1 that long. Second idea was a treated PSL spanning 30' at the midpoint on the 22'6 and hanging joists, but treated PSL sized for that application was $42+ per foot (over $1300) plus the footings, posts, and hardware to hold it up. Next idea would be a built up beam in place of the PSL, but I could use some advice for calculating the size and assembly. Deck is 22.66x30=680s.f.. Code says 40/10 loading so 680*50=34000 lbs total loading. Divide by 3 gives me center beam load of 11,333. My joist span being under 11 now, I determine that I need 2x8 #2 joists at 16"OC. My 30' beam divided by 23 joists gives me just under 500 lbs every 16" as an evenly distributed load.

Now for the question. Assuming all of the above calcs are correct (think so, but will humbly accept any corrections), how big of a built up beam do I need (size and composition), how many piligs supporting it, how big should the pilings be, and how do you arrive at this answer?
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Old 09-06-2008, 08:19 AM   #2
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Re: Sizing Built Up Deck Beams


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Originally Posted by Unforgiven View Post
how big of a built up beam do I need (size and composition), how many piligs supporting it, how big should the pilings be, and how do you arrive at this answer?
Oh that's an easy one. I call my engineer.

I thought you were saving a few bucks 'cause you were gonna be the engineer? Well...go be one.

Mac

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Old 09-06-2008, 09:16 AM   #3
 
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Re: Sizing Built Up Deck Beams


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Originally Posted by BuiltByMAC View Post
Well...go be one.

Mac
I know I'm new to this forum, and the new guys get the smarta** answers from the regulars, but I was hoping for a more intuitive answer. I'd like to think that I can arrive at a beam size without college degree in material sciences and engineering. I suppose I could call an engineer and pay him $1000 to design my structure for me, but then I wouldn't be any smarter than I was before I wrote the check. I don't just want an answer, I want to know how to find it myself in the future.
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Old 09-06-2008, 09:34 AM   #4
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Re: Sizing Built Up Deck Beams


HERE WE GO, first off, are you really going to accept an calc from a stranger on the internet, then go build according to this strangers post, put your name on the job, and take all responsibility for the structures success, or failure. there are many llegal reasons to consult an engineer on this one, if something went wrong, you would be WISHING you could spend that $1000 to get out of it. for most of us who have been building for many years, a project like you describe would be very easy to calc out, our experiance would allow us to build ( probably overbuild) most structures just based on our experiance, and knowledge. if it is a project for myself i would be very comfortable designing and building ANYTHING. for a client, i want the security of a paper trail to protect what i have worked so hard for .G
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Old 09-06-2008, 10:15 AM   #5
 
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Re: Sizing Built Up Deck Beams


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Originally Posted by genecarp View Post
HERE WE GO, first off, are you really going to accept an calc from a stranger on the internet, then go build according to this strangers post, put your name on the job, and take all responsibility for the structures success, or failure.
I would research the method outlined and verify the formulae through other sources. I am very thorough. Of course I could over-engineer something and hope nobody asked for the methods I used to reach my determinations, but I would rather learn the proper way to size a beam, and unfortunately I can't apply for a permit based on telling the building official that I have experience and knowledge and hope he'll just trust me on the beam sizes. I, like you, have been building for many years, and have lots of experience, intuition, and knowledge and know better than to assume anything. If you can easily calculate this beam size would you care to share that knowledge with a fellow construction professional?

Last edited by Unforgiven; 09-06-2008 at 10:25 AM.
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Old 09-06-2008, 10:42 AM   #6
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Re: Sizing Built Up Deck Beams


i just don't get the whole "saving money by doing it myself" mindset, then hopping on here (after having never been here before) and asking us to engineer it for you for free.

What's our motivation to do your job for you?

(I know, I know, now you're gonna get mad 'cause we're not helping our fellow man out enough...hmmm, seems a bit familiar)

Quote:
I'd like to think that I can arrive at a beam size without college degree in material sciences and engineering.
Yeah, what the hell do we need engineers for anyway? That stamp on the plans is just another way that the Man keeps us down...

Mac
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Old 09-06-2008, 11:38 AM   #7
 
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Re: Sizing Built Up Deck Beams


If you don't care to add value to the discussion then feel free not to. I'm not asking anyone to do my job for me, I'm asking direction and advice on how to make determinations. That's what we do on forums, we exchange information and talk about solutions. I've been a veteran contributor on other forums for many years, and have found that if I don't care to add value to a discussion, or do not have value to add then I simply don't post.
If someone would care to post relevant information I would be very interested in reading it and appreciative of their time.
In my locale it is not required to supply sealed engineered plans for projects under $25K in value. I employ engineers on a regular basis for many tasks, and build structures of many different types, and if I called one of my engineers he would probably give me the info over the phone and for free. I was simply hoping to come across a fellow tradesman or builder with info to share.

Last edited by Unforgiven; 09-06-2008 at 11:40 AM.
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Old 09-06-2008, 12:14 PM   #8
 
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Re: Sizing Built Up Deck Beams


If you have a regular lumber company that you deal with. I might suggest asking them if they would run this by their suppliers.

Lumber wholesale suppliers such as Snavely, Louisiana-Pacific, Weyerhaeuser ect.have engineers on staff who will do sizing for you at no cost just use their materials.

They do all my second story and roof work at 0 cost you do need a plan showing your dimensions and spans in order for them to be specific.

Google some joist span calculators and beam as well quite a few out there I have some that I tried to post but it will not let me until I have made so many post to this site

Good luck

Last edited by Tex Remodeler; 09-06-2008 at 12:38 PM.
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Old 09-06-2008, 12:22 PM   #9
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Re: Sizing Built Up Deck Beams


I wanted a big new truck, to save a little money I bought a Yugo hatchback, I'm not really happy with the results, any ideas?


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Old 09-06-2008, 04:32 PM   #10
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Re: Sizing Built Up Deck Beams


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Originally Posted by Unforgiven View Post
I employ engineers on a regular basis for many tasks, and build structures of many different types, and if I called one of my engineers he would probably give me the info over the phone and for free.
That's awesome, dude! I work with a guy here in town but he still makes me pay every time I want to use his services. Of course, he wants a set of plans to work off of, he won't give me any info over the phone - there's that whole liability issue...

Looks like you might have to wait until Monday to call your guy and get the answers you're looking for.

Here's a thought, why don't you run (3) 22'-8" beams from CMU wall to CMU wall - one at 0', one at 15', and one at 30'. You've now got a joist span of 14' and change. That's doable using 2x10 SYP @ 16" oc. Joists would run parallel w/ the CMU walls and you'd have no posts down in the smoking area.

'Course I still can't help you with the beam sizes, so really, what good am I?

Mac
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Old 09-07-2008, 02:47 AM   #11
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Re: Sizing Built Up Deck Beams


There is a book out there, Basic Engineering for Contractors, that may have the info you need.

But seriously, for spans like that, you should consider calling your engineer on Monday.
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Old 09-07-2008, 06:13 AM   #12
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Re: Sizing Built Up Deck Beams


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If you don't care to add value to the discussion....
The value Mac is giving you is saving you from litigation for your beam failure.

How much is that worth?

Get a ****ing engineer. This isn't a game.
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Old 09-07-2008, 06:23 AM   #13
 
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Re: Sizing Built Up Deck Beams


After using all of the information I've found I've come up with a 4-ply beam of 2x12. Someone was kind enough to turn me on to a program called BeamChek that has given me a much greater understanding of the forces generated and how they are quantified. Thanks, Redwood, for the book recommendation. I'll be getting that soon, today if Books A Mil has it. Regardless of my findings, or how confident I am in them, I will be having the eng. check my work.
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Old 09-07-2008, 08:52 AM   #14
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Re: Sizing Built Up Deck Beams


Sooooo Funny Mickey!!! I like the bi line too major grins.

Its a deal building with pt lumber, make up the beams to use with less foundation and you get more movement, use smaller lumber more foundation less movement, higher costs = losing the bid to Compatition.

I built a big ol girl earlier this year with double sized 2x12s clamped together,fastened with construstion adhesive landing on 2'x2' piers 10' span. It got a little hot over here in cow town I really gave my power planer a work out leveling out the top of those beams and I never did get it completly right. The Wallet was happy and the thing looked good with the ipe on but if I had it to do again I would use smaller lumber with a 6' span/more foundation.

Its one thing to look up stuff in a book, Its a whole nother smoke to learn it by doing it and being trained while working by the hour for a few years.
I cant see anything wrong if a poster like this would combine his questions with an offer to pay for that advice either public or private.

I my very own self have been pleasured this way ranging from two grand or so for baby sitting the Project from the ground up to credit at the local wine store for some inside tricks installing ipe. Bang Bang everyones happy!! the cost is less than the desk jockey with a span book,the advice is battle ground proven, the poster learns things that took years to learn, everyone walks away with something. J.
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Old 09-07-2008, 09:48 AM   #15
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Re: Sizing Built Up Deck Beams


Quote:
Originally Posted by redwood View Post
There is a book out there, Basic Engineering for Contractors, that may have the info you need.

But seriously, for spans like that, you should consider calling your engineer on Monday.
Yeah, after 25 years of trips to
the architectural bookstore,
and hundreds of $ dropped on
text books, I found that.
And he doesn't even give you
a headache and eyestrain for
your efforts.
Now, with this here internet thingy,
you can find practically anything
you need for free.
(Well, it might require some effort.)
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Old 09-08-2008, 05:43 AM   #16
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Re: Sizing Built Up Deck Beams


Quote:
Originally Posted by Unforgiven View Post
After using all of the information I've found I've come up with a 4-ply beam of 2x12. Someone was kind enough to turn me on to a program called BeamChek that has given me a much greater understanding of the forces generated and how they are quantified.
Not to dis the program, never used it, but I think that beam is too small. My span tables only go to 18' between piers & it would barely work at that span & you're going another 4'-5'. (Edit: Not to mention my calcs were with residential live & dead loads. I think this would be considered commercial. Those loads are usually higher if I recall.) If you insist on doing that span CALL AN ENGINEER. See if your buddy would cut you a deal. I would not even trust a program I got off the internet unless it a was from a very reliable source & I knew exactly how to run it. One wrong value & it comes crashing down.

Why not add a pier in the middle of the beam span? Dock piers aren't that hard to do, unless you have a fear of water. Do you know how to calculate pier size? Have your engineer do that while he's at it. Get your $1,000 worth.

Last edited by Danno6102; 09-08-2008 at 08:56 AM.
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Old 09-08-2008, 07:11 AM   #17
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Re: Sizing Built Up Deck Beams


It is true that Weyerhaueser, Trus-Joist, Nascor, etc have paid engineers on staff at their wholesalers that will do this work for home builders. The I-joists are generally shipped at railcar length and then cut to order based on the engineer's calcs. But all of this is for interior stuff.
The only exterior engineered beam I know of is the Rosboro Treated Glulam. Obviously I have never worked with it, but the Rosboro people are always nice to me at trade shows. The one guy even bought me a beer once!
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Old 09-08-2008, 09:03 PM   #18
 
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Re: Sizing Built Up Deck Beams


These Rosboro chaps seem like my type of guys. My lumber supplier has never heard of them, which I guess isnt that far off base since they're in Oregon.

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