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Old 02-09-2009, 11:59 AM   #1
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Cutting a beam flange


I'm planning a job to replace a support wall in a friends house. It's on the first floor with a spare bedroom above it. Using span tables, a W6x12 (6” deep x 4” wide) steel beam will work for the load (just under 12' span, 12' tributary length). I plan to bury the beam in the joists for aesthetics and head room, so the beam has to fit in the 2 x 8 joists.
My plan is to use a W6x15 beam, the thickness and depth are the same but the flanges are 2” wider. I’d like to cut (rip) the top flange by 1.5” on each side so the joists can rest on the bottom flange. The beam should still be strong enough, and I think this would be easier than lining up hangers on the top of the beam, since they would have to be attached before putting the beam in place, or packing out the beam and then attaching hangers.
I guess I want a reality check. I’ve seen where joists were notched on top to rest on beam bottom flanges, and I’ve heard of welding or bolting a wider plate on the bottom of a beam, but never cutting back the top flange.
A) Will I be able to cut the flange with a Freud Metal cutting blade on a circular saw and
B) Would this be easier than lining up hangers?

Thanks for any input

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Old 02-09-2009, 12:49 PM   #2
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Cutting a beam flange


First issue is you need to file for a permit.

Second issue is that when you file for the permit, the town is going to ask to see a drawing signed and sealed by a PE.

Third issue is you haven't described how the joists will be affixed to the beam, which must happen. They can't just rest there on the lower flange.

Fourth issue is that you can't jump from a W6x12 span table to a notched W6x15 beam. Engineering doesn't work that way.

Fifth issue is since this isn't your home, and the homeowner isn't performing the DIY work, you have to make sure you comply with state and local regs concerning licensing and insurance.

The right thing to do is to spend the couple hundred or so and have a licensed PE design this properly for you.


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Old 02-09-2009, 06:01 PM   #3
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Cutting a beam flange


devlin,

You can have your beam fabricator put holes in the web so that you can bolt in lumber to pack out the area between the flanges.

Placing the hangers on the packed out beam after it has been put in place is not that difficult with a palm nailer. You will have supported the floor joists on both sides in the correct position and cut the length so that the packed out beam just slides into place. It's easiest if you can have someone else hold the hanger in place while you nail the first couple nails on the hanger.

Plan the location of the bolts so they don't coincide with a joist hjanger location if possible.

Hangers have got to be alot easier than cutting a beam.
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Old 02-09-2009, 06:37 PM   #4
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Cutting a beam flange


I'm curious as to why you wouldn't just run your saw blade across the end of the 2 x to dado out a deep 3/4" groove that the upper beam flange would slide into. It's been done that way for decades.

This gives you plenty of floor nailer above the beam. And there are many different ways of setting up attachment schemes.
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Old 02-09-2009, 07:33 PM   #5
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Cutting a beam flange


Aside from the engineering aspects, cutting 24' of beam flange isn't going to be a picnic either. Those blades are typically used for up to 1/8" thickness on ferrous metals. That flange will be at least double that.
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Old 02-10-2009, 07:21 AM   #6
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Cutting a beam flange


Aggie,
Third issue; I planned to run strapping on the bottoms of the joists, across the bottom of the beam, to tie them together. It's not a solid connection, but between that and blocking between the joists they should say put?

jogr,
Yes, that's a good point, putting up the hangers after the beam is up should be easier than attaching them and trying to slide beam and hangers in like a puzzle. I was just trying to avoid a lot of the overhead work. Cutting the beam, I could take my time, make a couple of passes if I needed to, working on the ground.

Willie T,
Nice (and nice drawing), but I can't, the joists are in place and the beam has to slide up from the bottom; no room to slide in from the side.
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Old 02-10-2009, 07:44 AM   #7
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Cutting a beam flange


All good reasons to completely re-evaluate this project thus far.

Aggie is 100% right, you need a structural engineer. What you describe is not how this is normally done, and you need the support of a professional. You also do need a stamped design in order to secure a permit.

I have seen engineers design inverted T (modified W-shape) support beams. It can be done, but cutting the beam severely weakens it, so that must be taken into account.

As for cutting the flanges of the beam yourself, ha! You have no idea what you're biting off, and your cutting method will not work. This is why they have torches and plasma cutters.
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Old 02-10-2009, 08:04 AM   #8
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Cutting a beam flange


KC,
You're right, what I really want is an inverted T, either cut fom a W or built up from 2 angles bolted back to back. I ran the second option through beam calculation software and got a reasonable answer, but that is even further from a standard beam, I would have to talk with a structural engineer before I felt comfortable with that.
That kind of felt like a slap of reality in cutting the beam! Another option there is to have my fab shop make the cuts. Of course, now I want to go buy the blade just to try it, Freud makes a Steel Demon blade that says it cuts up to 1/4", but mild steel (flanges are 1/4"). I'll have to figure that one out before I commit.
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Old 02-10-2009, 08:07 AM   #9
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Cutting a beam flange


We're not talking about mild steel here. Sorry to slap you with reality...Not tryin' to hurt you!
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Old 02-10-2009, 08:14 AM   #10
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Cutting a beam flange


Actually, I was thinking it was just what I needed. I'm thicker skinned than that!

And thanks for your replies.
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Old 02-10-2009, 01:25 PM   #11
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Cutting a beam flange


Quote:
Originally Posted by devlin1k View Post
what I really want is an inverted T, either cut fom a W or ...
In the industry, that's called a WT beam, and they're specified in the same fashion: WT8x10 is a W8x20 cut in half.

Call an engineer, but if this were my house, I'd be sizing up a rectangular piece of tubing instead of a W shape, and reinforce it accordingly to take the span. At least then you could weld some angle clips vertically to bolt the joists to. Play it right, and the whole beam could be pushed up into place, and all you have to do is lag or carriage bolt through the angle iron clips and into the joists, and have the joists rest on a piece of flat stock welded to the bottom of the tubing.
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Old 02-11-2009, 07:01 AM   #12
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Cutting a beam flange


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Originally Posted by Aggie67 View Post
...and have the joists rest on a piece of flat stock welded to the bottom of the tubing.
See, that's what got me thinking about cutting back the top flange of a beam and resting the joists on the bottom flange. But your suggestion seems to take the heavy metal work from my beam idea, plus welding, and combine it with the complication of pre-installed hangers or clips that have to fit just right (but it does provide a solid connection to the beam). How about 2 angles, back to back? Then I can cut a slot in the joists and just slide it up in place. Run strapping underneath, across the bottom of the angles from joist to joist to hold them in place, and the joists would have a lot of bearing (say 6" on 6 x 6 angles).
Yes, I would have to have an engineer look at that plan. Right now I'm thinking of a more conventional packed out W.

Thanks
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Old 02-11-2009, 07:40 AM   #13
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Cutting a beam flange


For such a short span and relatively short tributary load, why not look at a wood beam? LVL, PSL, or glulam could be used. The only drawback would be that the header would be deeper than the existing floor joists, but installation would be straight forward.
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Old 02-11-2009, 07:42 AM   #14
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Cutting a beam flange


Quote:
Originally Posted by devlin1k View Post
See, that's what got me thinking about cutting back the top flange of a beam and resting the joists on the bottom flange.
That's not very economical. In the trades, cutting something and producing waste is exactly what you want to avoid. Plus I would never put my seal on that kind of idea. Just not the way it's done.

Quote:
Originally Posted by devlin1k View Post
How about 2 angles, back to back? Then I can cut a slot in the joists and just slide it up in place. Run strapping underneath, across the bottom of the angles from joist to joist to hold them in place, and the joists would have a lot of bearing (say 6" on 6 x 6 angles).
Two angles back to back would never have the load capacity of a W shape or rectangular tube, unless it was a huge piece of angle. Again, just not the way it's done.

Quote:
Originally Posted by devlin1k View Post
Yes, I would have to have an engineer look at that plan. Right now I'm thinking of a more conventional packed out W.
That's much more conventional. Then you can attach joist hangers to the face of the wood. Go to a site like i-header.com and get some ideas.
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Old 02-11-2009, 07:53 AM   #15
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Cutting a beam flange


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