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Old 05-22-2014, 10:08 AM   #1
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sizing a roof steel beam to span 15', OR equivalent size for 3-ply 11-7/8 LVL


Hi Everyone,

I'm looking at building a roof over a deck this summer near Ottawa, Ontario, Canada. I'm looking for some help sizing the steel I-beam (W type) to span 15'.

I've attached a picture of what it may look like, though the post on the right will be a bit further to the right, and the steps will come straight out, not off to the side.

Beam will be supported on two 6x6 posts
Beam span 15'
2x8 rafters 16" o.c.
rafter span (to house ledger board) 11.5'
roof slope 3:12

I've already sized an LVL but am now hoping to use steel to reduce my depth of the beam. I don't want it to block our sight line too much when looking out from the patio door.

I haven't found many steal beam span tables out there, like there are for wood/LVL products. Can anyone give me a hand? My best guess at it is a W6x20

LVL was sized to be a 3-ply 1-3/4 x 11-7/8, so a 5-1/2 x 11-7/8 LVL. So, if anyone knows of any equivalency tables to 'convert' an LVL to an equivalent steel beam, please share.

Thanks.





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Old 05-22-2014, 02:08 PM   #2
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sizing a roof steel beam to span 15', OR equivalent size for 3-ply 11-7/8 LVL


Steel beams are not normally sized from tables, they are sized according to fundamental principals of mechanics. Typically to size a steel beam you need to know the loads, and you need to know the code you are operating under (the steel code, may not be referenced in the residential code). The steel code will give you the required safety factors for the loads. Steel beams codes typically allow working stress methods, or LRFD (Load and Resistance Factor Design), sometimes they allow either to be used.

Asking someone on an internet chat forum to size a steel beam for you is a bit out of the ordinary. Anyone with a license (like me) is prohibited by law and ethics from performing structural analysis without a contract and without a site visit, so the only people on here who might be willing to offer advice are unlicensed, and may or may not understand how to size the piece. How are you going to know?

My suggestion is you find a local steel yard with a resident engineer, or an on call engineer. They may be willing to roll up the cost of design into the price to fabricate the piece for you. The yard will fabricate the piece, drill the required holes for bolting the piece in place, and load the piece onto your pickup truck. I have purchased several I beams over the past few years from a local yard, the service was good, and the steel saved me several valuable inches as a header.

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Old 05-22-2014, 04:08 PM   #3
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sizing a roof steel beam to span 15', OR equivalent size for 3-ply 11-7/8 LVL


Looking at your span and tributory loading, I would say you would need something like an 8" deep beam, which is probably shallower than an equivalent LVL beam. But as above, you need to get it confirmed.

Perhaps more important is how you fix the beam to the posts?

Have you considered a channel section?
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Old 05-23-2014, 12:43 AM   #4
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sizing a roof steel beam to span 15', OR equivalent size for 3-ply 11-7/8 LVL


Quote:
Originally Posted by tony.g View Post
Looking at your span and tributory loading, I would say you would need something like an 8" deep beam, which is probably shallower than an equivalent LVL beam. But as above, you need to get it confirmed.

Perhaps more important is how you fix the beam to the posts?

Have you considered a channel section?
Apparently you don't have a licence? I sure wish there was a sticky saying don't ask for span ratings!
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Old 05-23-2014, 06:18 AM   #5
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sizing a roof steel beam to span 15', OR equivalent size for 3-ply 11-7/8 LVL


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Originally Posted by Nailbags View Post
Apparently you don't have a licence? I sure wish there was a sticky saying don't ask for span ratings!

Not for practicing in US, but where I am, a licence to practice is not needed. Local authorities here have their own checking engineers to go through any calculations submitted, so figures are always double-checked.

OP asked for approximate depth of beam - that's what I replied with - together with the obvious rider that he should get it checked; no problem
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Old 05-23-2014, 10:36 AM   #6
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sizing a roof steel beam to span 15', OR equivalent size for 3-ply 11-7/8 LVL


DIY,

in the States steel beam sizing is typically required to be certified by a professional engineer since building codes typically do not contain a span chart for sizing (as mentioned by Daniel). you may want to check with your building department to determine if your use of a steel beam would require an engineer's certification or not.

good luck.
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Old 05-23-2014, 11:09 AM   #7
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sizing a roof steel beam to span 15', OR equivalent size for 3-ply 11-7/8 LVL


And any welds have to be inspected.

Playing with steel is a whole new ball game.
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Old 07-28-2014, 11:07 AM   #8
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sizing a roof steel beam to span 15', OR equivalent size for 3-ply 11-7/8 LVL


In this case the steel tin shade be a proper way to well arrange them and with the help of nut bolt easily screwed it .
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Old 07-28-2014, 04:22 PM   #9
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sizing a roof steel beam to span 15', OR equivalent size for 3-ply 11-7/8 LVL


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Originally Posted by garykerr View Post
In this case the steel tin shade be a proper way to well arrange them and with the help of nut bolt easily screwed it .


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