28' Clear Span For Elavated Deck/porch

 
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Old 07-21-2008, 03:39 PM   #1
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28' Clear Span For Elavated Deck/porch


Can anyone help with the requirements to clear span 28' for a deck? The deck would attached to the house on on side and supported by columns on the 2 free standing corners. The customer would like "NO" other post under the deck. I found several calculators on line but none would allow for this calculation.
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Old 07-21-2008, 04:38 PM   #2
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Re: 28' Clear Span For Elavated Deck/porch


I can only presume you will know nothing on this forum will substitute for an engineer's calculations and design. The prevailing code, with deflections would be the primary consideration, not to mention the potential loading of 784 sq/ft of deck....like capacity in people? The liability to this would be enormous.....without a sealed engineer's specifications, this is a no brainer, like no way.

I bet if you have an engineer look at this, it will some back with 16 inch I beams on columns that can support 20 kips or more......concrete piers, the whole works.

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Old 07-21-2008, 04:42 PM   #3
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Re: 28' Clear Span For Elavated Deck/porch


Steel is the only way I know to make that span, but not to worry this will be a high $ job you should be able to take some major change home. J.
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Old 07-21-2008, 04:56 PM   #4
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Re: 28' Clear Span For Elavated Deck/porch


No way can you span more than 26' with a 2"x12". Look into the american wood council for explanations of these limits etc. I dont know where you live but snow load considerations also come into effect as do the amount of people on the thing. One thing you definetly dont want is to worry about that if they are having a party one day. that being said you can go to a local book store and grab a basic construction engineering book that goes into great detail. maybe you can talk them into a slightly smaller deck but I dont even know where you could get a pressure treated board 26' long anyhow??? Your best bet for a deck this size is to sink steel columns in solid rebar tied footers, then put I-beams across those to cut that 28' in half. then frame your pressure treated deck on top of the steel. It prob will be comparable in price (no long 2x12's) put standing seam metal roofing on the underside to hide the craziness above and catch water to a gutter system. just some ideas?? good luck...hire a good welder if you cant weld. most steel suppliers have a smal crane truck to put it up while you weld. Erich
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Old 07-21-2008, 05:03 PM   #5
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Re: 28' Clear Span For Elavated Deck/porch


Let the owner know about the cost and footings and deck construction. The depth of the beam will also cut off light compared to a more reasonable span if he has a patio/walkout below. Also, the steel beam will be strong enough, but you will get more deflection and bounce, which is something that an engineer can not really be accuarte about in a design.

After the owner chokes, you can come back and give him a more reasonable proposal/solution with 1 or 2 posts and wood beams. I am sure you can make the job go a lot faster, be more predictable and make a good profit. You could also end up with a satisifed customer to use for referrals.

If he insists on the long span steel beam you can always have it fabricated and have it erected.
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Old 07-21-2008, 08:00 PM   #6
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Re: 28' Clear Span For Elavated Deck/porch


We did one last year, 16ft 2x12 joists from house 12oc, 26' 7" front beam, posts on either end. We had our supplier spec the beam and if I remember correctly it was a double treated 3-1/2" x 16 parallam. All I remember was it took a bunch of bolts and adhesive to assemble and then we brought in the crane as we assembled it up the hill on the side of the house and flew it over the end of the house and down to the posts. I think my rigger said we were right around 3000 lbs.

Love to watch the customers eyes when they see a 28ft beam flying opver their brand new house.
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Old 07-21-2008, 08:13 PM   #7
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Re: 28' Clear Span For Elavated Deck/porch


Whats wrong with getting a PT Parallam out of the question? I think it is, but I am not an expert. Call your local lumber yard and have them spec one out.
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Old 07-21-2008, 10:00 PM   #8
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Re: 28' Clear Span For Elavated Deck/porch


Quote:
Originally Posted by Alwaysconfusd11 View Post
Whats wrong with getting a PT Parallam out of the question? I think it is, but I am not an expert. Call your local lumber yard and have them spec one out.
It isn't about what material will make the span, as much as the use. I would not consider any glue lams or micro lams...anything like that, simply because of the exposure.

This project would need engineering, period. Can you imagine designing this deck, and getting through code and permits? What is the capacity? Snowfall? Any wind factor (uplift)?

The liability on this one would make me cringe....I wouldn't touch it without an engineer's stamped drawings.
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Old 07-21-2008, 10:04 PM   #9
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Re: 28' Clear Span For Elavated Deck/porch


Quote:
Originally Posted by joasis View Post
I wouldn't touch it without an engineer's stamped drawings.
I wouldnt either, I am just making discussion.
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Old 07-21-2008, 10:15 PM   #10
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Re: 28' Clear Span For Elavated Deck/porch


When we did the job last year I had the lumberyard run the calculations and spec the beams, I also followed up with Weyerhaeuser who verified the specs and supplied my inspector with all of the documentation on size and treatment. While getting an engineer involved is a good idea in many situations when it comes to wood beams the lumberyard and the manufacturer have always been good enough for me. I figure if they cannot figure out their own product then we have problems. As for exposure Weyerhaeuser tells me that parallams will not have any adverse problems with exposure. By the way I did check with an engineer and he would have charged me more that I paid for the beams to do the calculations.
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Old 07-21-2008, 10:23 PM   #11
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Re: 28' Clear Span For Elavated Deck/porch


It can be done! I just specd out a 45' beam that weighed almost 1300 pounds!!! It will cost u roughly $35 a LF or $70 a LF for treated but it may be cheaper it might not have to be as thick or wide as the one I was specd out to use. Go to your supplier if they are really good they can spec it out in one of there load books, etc n call the manufacturer to confirm it n order it. It will take about a week to get n a piece of equipment to set it in place!!! Have fun you better have very intelligent Carpenters n some big bulls to hump it into place for lift! Oh yeah you will have to have the beam and footers drawn up by an architect n the building department may require you to have the drawing stamped by an engineer!!! Charge, Charge, Charge!!! A whole lot of work for just that look of 2 posts your client is requesting!!! U may want him to pay for all the materials n just increase your profit margin on the rest bc he will not have any clue or willingness to belive you when you submit your estimate n he asks why is it so high n you tell him that beam is gonna cost almost $1500 with material, equipment, etc

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Old 07-22-2008, 05:40 PM   #12
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Re: 28' Clear Span For Elavated Deck/porch


I dont think a parallam beam is gonna do a damn bit of good here. Isnt this guy talking about running a deck across a 28' span? what are you gonna do run paralams 16" on center? Run a beam parallel to the house on piered posts and 3 perpindicular and frame your pressure treated right on top of 2x6" plates laying flat and carriage bolted to the I-beams. way stronger than LVL I promise and it seems the easiest to me??? anybody agree?
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Old 07-22-2008, 07:02 PM   #13
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Re: 28' Clear Span For Elavated Deck/porch


I dont think I agree, but maybe I dont understand.
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Old 07-22-2008, 07:58 PM   #14
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Re: 28' Clear Span For Elavated Deck/porch


I dont think he ever said what dept of the deck is from house out. I assume the width is 28'. If it is no longer than 12' then 12'-2x12s sitting on a glue lam or I-beam under the rim would be fine. Or if it is up to 16' the beam can stay there and cantalever the joist 4'. I would go with steel if me. Steel is high now but proly cheaper than a special order treated lam beam that may or may not last anyway.
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Old 07-22-2008, 08:12 PM   #15
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Re: 28' Clear Span For Elavated Deck/porch


I think anything practical with that span
is going to be pretty bouncy with much
of a load on it.
I know the long span glue lams are.
I know they do it out west,
but I never considered LVL's or
Paralams for exterior use.
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Old 07-22-2008, 08:39 PM   #16
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Re: 28' Clear Span For Elavated Deck/porch


Quote:
Originally Posted by John Hyatt View Post
Steel is the only way I know to make that span, but not to worry this will be a high $ job you should be able to take some major change home. J.
sorry to dis agree, but as a welder I can say that unless you give steel support it can not support its own weight. case in point, we were to build a hayloft for a farmer. he did not want a bunch of posts in his barn so he got a piece of 16" steel I beam about 40 foot long and thought to set it on 2 posts! Thats right, 2 posts. I tried to tell him, but he was the one with the money. The lift came in and set the beam and when the lift let go the beam sagged. needless to say he was red faced. We wound up placing a few more posts to support the wight.
The way the engineers do it is to have a pre formed bend placed into the steel. dont believe it? just look at any empty flatbed tractor trailer going down the road. The trailer bends upwards in the middle.
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Old 07-22-2008, 11:33 PM   #17
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Re: 28' Clear Span For Elavated Deck/porch


Quote:
Originally Posted by GGCLLC View Post
Can anyone help with the requirements to clear span 28' for a deck? The deck would attached to the house on on side and supported by columns on the 2 free standing corners. The customer would like "NO" other post under the deck. I found several calculators on line but none would allow for this calculation.
Check out this site from a company called, "Better Header". Click on, "Beam Lengend" and that will give you an idea of what they have. Might be worth checking into.



http://betterheader.com/ibeam.asp
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Old 07-23-2008, 05:44 AM   #18
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Re: 28' Clear Span For Elavated Deck/porch


Quote:
Originally Posted by USP45 View Post
The way the engineers do it is to have a pre formed bend placed into the steel. dont believe it? just look at any empty flatbed tractor trailer going down the road. The trailer bends upwards in the middle.
As does any Long-Span bridge.
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Old 07-23-2008, 08:31 AM   #19
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Re: 28' Clear Span For Elavated Deck/porch


Do not even touch it without having an engineer approve it. You are just asking for liability problems.
There are lots of solutions, as mentioned above: glu-lam, I-beam, paralam, steel, whatever. You are also going to have to put in humongus footings(I'd guess 30" dia).
Tell the customer he'll have to pay for engineering drawings, consulting, etc.

OR, simply put one post in the middle and span the 14' with triple 2x12.
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Old 07-23-2008, 01:58 PM   #20
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Re: 28' Clear Span For Elavated Deck/porch


A HUGE part of it how far the joists span. If its 4' its a lot less loading than 16' Let us know what your joist span is as well as your loading requirments from your local building department.

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