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Steel I-beam with 2x8s on flange


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09-21-04, 02:46 PM   #1  
dunno
Steel I-beam with 2x8s on flange

I have an 8x8 steel I-beam running down the center of my basement under the first floor load bearing wall of a small ranch. There are 2x8 floor joists
running into each side of the I-beam sitting on the flange. The 2x8s are 24"
OC spanning approx 12.5'. I am unable to secure the 2x8s to the beam and they need to be beefed up. My plan is to brace the floor joists on either side of the beam, brace the load bearing wall on first floor, slide the 8x8 beam out through the wall into the garage, this is the way it was installed, sister another 2x8 to each joist, slide in a 10x10 I-beam to allow me to have a 2x4 sill plate on each flange to attach the joists too. Does this sound like a good plan? I need the joists inside the beam for headroom. When I sister 2x8s can I bolt through the middle 3rd of the joists?

Thanks
dunno

 
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09-21-04, 05:14 PM   #2  
Let's see, your sistering the FJ and adding two inches to the WF, which takes 2" off the distance from the floor to the bottom of the 1010WF, decreasing your headroom,.....for headroom?

 
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09-21-04, 06:38 PM   #3  
dunno
The 2'' I lose in headroom is ok, I just don't have tall enough ceilings to put a beam under the joists. The 10x10 will give me a plate to secure the joists to plus a little more clear span between the lally posts. I can level it in the garage about 24" off the floor which will put me at ceiling height in basement.
I just have to figure a way to slide it in while supporting it on the inside. Maybe a floor jack in the garage and some kind of jack that is taller, but still rolls on the inside. Is it ok to bolt through the middle 3rd of joists if they are being sistered, or is nailing sufficient?

t/y
dunno

 
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09-21-04, 10:27 PM   #4  
Two more questions.

Whats a "lally" post?

Why are you doubling the floor joists?

 
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09-22-04, 11:50 AM   #5  
dunno
A jack post, steel support post, steel column. I'm doubling the 2x8s to gain some strength for the new floor I'll be putting in on the main level. They are spaced 24" OC, instead of 16" OC. I'm hoping that by doubling them it will be more rigid. I could put new ones in at 16 ", but thought that I'd have to cut some of the old ones out to do so. I could put one in between each one, but then it would be harder to work in the electrical, plumbing, etc... at 12" OC.
I never said this was a good plan, but I'm doing my best.

t/y
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09-22-04, 05:29 PM   #6  
Hire a certified welder familiar with field welding structural steel. He'll be able to weld the joist pockets to the WF for you.
With FJ's at 24" oc., you should have at least 3/4" floor sheating. Rather then sistering the joists, in stall 2x4's at 24"oc between them.

Its expotentually safer.

 
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09-23-04, 12:41 PM   #7  
dunno
These are 2x8 joists that span 12.5' on both sides of the beam. The other end of the 2x8s rest on the concrete wall. It's like a rectangle with the I-Beam down the center and the joists running out to the block walls on either side. Are you saying to run 2x4s in between and parallel to each 2x8 with a span of 12.5'? I was told, by my local lumberyard, that 2x8s at 24" OC are
not strong enough to bear the load, and that I should double them. Wouldn't
this be stronger than 2x4s? Also in one of my earlier responses I stated that
I could put another 2x8 in between, but that doesn't leave me much room for electrical, etc... I'm going to put in the 10x10 beam with holes drilled in the bottom flange every 2' to fasten the 2x? plate too, and then double the joists and secure them to the plate. Thanks for your responses but they're not very helpful. Maybe I need a concrete contractor for answers. I still don't know if nailing or bolting should be used to sister the joists,or if I can bolt to
the middle third of the joists..
thanks anyway,
dunno

 
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09-23-04, 05:16 PM   #8  
[QUOTE=dunno]These are 2x8 joists that span 12.5' on both sides of the beam. The other end of the 2x8s rest on the concrete wall. It's like a rectangle with the I-Beam down the center and the joists running out to the block walls on either side.

So nothing has changed from your original post, thats encouraging.

Are you saying to run 2x4s in between and parallel to each 2x8

No, I did not say from bearing point to bearing point, I said,"Rather then sistering the joists, in stall 2x4's at 24"oc between them.",IE., from one joist to another. This would add additional support to the floor sheating.

I was told, by my local lumberyard

Wonderful.

Did this individual show you the span tables from the relevant issue of the building code for your municipality, were you explained to, "span" or "greatest moment", were you shown certification that this individual was a qualified building inspector?

that 2x8s at 24" OC are not strong enough to bear the load, and that I should double them.

SPAN; (In general) As it applys to your condition, is from the OUTSIDE of your foundation to the CENTERLINE,(CL),. of the 8WF.
In reality, it is from the CL to CL of the supports, for the qualification of "full bearing".

GREATEST MOMENT: This occurs at the exact spot where the framing member intersects the support. In your case, the inside edge of the cinder block and the closest edge from that point of the 8WF and is defined as the greatest moment because it is where the greatest weight is carried.

For practical purposes and using the "general" application of determining allowable span, 2x8 at 24"oc. Douglas fir larch, #2 or better, supporting drywall walls, will span about 11' 3".

However, and because of the use of the 8WF, this was built to a set of plans signed by an engineer and accepted by the building dept., thereby defining the building depts responsibility as insuring that the portion of the construction addressed by that engineers calculations and signature, are accomplished pursuant to those calculations.

If the engineer used the "greatest moment" method of determining allowable span, the actual span would then have been reduced by the width of the CMU's and half of the width of the 8WF.

Additionally, "select structural" may have been specified.

I'm going to put in the 10x10 beam with holes drilled in the bottom flange every 2' to fasten the 2x? plate too, and then double the joists and secure them to the plate.

Spend your money.

Thanks for your responses but they're not very helpful.

You are quite welcome. You could have saved us both a lot of time by simply paying a visit to the local building department and educating yourself.

I still don't know if nailing or bolting should be used to sister the joists,or if I can bolt to the middle third of the joists.

Generally you stager 16D from both sides, in opposition. You might check with the lumberyard, not the building dept., to verify.

A correct decision, is an informed decision.

Go with my blessings.

 
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09-23-04, 07:31 PM   #9  
dunno
The house was built by a farmer in the 1940s. No engineer involved.
It's easier to sister a 2x8 rather than cut 2x4s to run between them, also
there's less chance of a squeaky floor on the main level if you don't have all that blocking. The only span I'm concerned with is from the wall to the beam,
whether that be greastest, bestest, or any other name someone wants to call it. By the way the 8x8 was put in by me, no engineer involved there either, amazing isn't it? I just wanted to know if there was an easier way to do it, but so far I've just had to explain lally posts, 2" of lost headroom, and probably a few misssspelled words along the way. Thanks for correcting my grammar, and definitions, but I sure would be glad if someone would submit a reply offering some practical advice. Thanks for all the time you've spent exposing my ignorance, but I have a beam to install.

 
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