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Old 03-19-2010, 12:13 AM   #1
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Engineered I-Beams


What is the maximum hole size I can cut in an engeered I-Beam? I would like to cut a hole in the web for an air duct. the literature says I can cut a hole 1/4 inch to the flange. I am talking about a single hole in two ajacent beams. Is this correct?
Thanks.

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Old 03-19-2010, 12:46 AM   #2
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Originally Posted by tonycinque View Post
What is the maximum hole size I can cut in an engeered I-Beam? I would like to cut a hole in the web for an air duct. the literature says I can cut a hole 1/4 inch to the flange. I am talking about a single hole in two ajacent beams. Is this correct?
Thanks.
If you look closely, you may be able to see a perforated outline of circles in the web. Just punch those out with a hammer.

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Old 03-19-2010, 03:05 AM   #3
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Engineered I-Beams


I was not able to see any hole knockouts . I was looking to make a 4 to 5 in dia cutout.

Thanks
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Old 03-19-2010, 02:39 PM   #4
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Engineered I-Beams


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Originally Posted by tonycinque View Post
I was not able to see any hole knockouts . I was looking to make a 4 to 5 in dia cutout.

Thanks
I would go no bigger than 3" on the center line.
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Old 03-19-2010, 02:53 PM   #5
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Engineered I-Beams


Quote:
Originally Posted by tonycinque View Post
What is the maximum hole size I can cut in an engeered I-Beam? I would like to cut a hole in the web for an air duct. the literature says I can cut a hole 1/4 inch to the flange. I am talking about a single hole in two ajacent beams. Is this correct?
Thanks.
sounds right to me. the web has very little to do with the strength of the beam. The primary purpose of the web is to hold the flanges apart and keep them from sliding. A big circle wont do much hurt that. square cuts will have a greater effect because the stresses will localize at the sharp cuts. The best thing to do is if at all possible, keep the holes out of the middle 3rd of the beam because that is were the beam is under the most strain (assuming normal loading and suports)

some of the beams come precut for ducting and have monsterous Oval holes cut in them.

based on what you are saying, a 5" cutout should be no problem for a 10" or larger beam (assuming 2" flanges and a 10" beam maxe size = 10"- (2x1/4"(flange clearance)) - ( 2x2"(flange size)) = 5 1/2"

Last edited by forresth; 03-19-2010 at 02:57 PM.
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Old 03-19-2010, 05:23 PM   #6
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Originally Posted by forresth View Post
sounds right to me. the web has very little to do with the strength of the beam. The primary purpose of the web is to hold the flanges apart and keep them from sliding. A big circle wont do much hurt that. square cuts will have a greater effect because the stresses will localize at the sharp cuts. The best thing to do is if at all possible, keep the holes out of the middle 3rd of the beam because that is were the beam is under the most strain (assuming normal loading and suports)

some of the beams come precut for ducting and have monsterous Oval holes cut in them.

based on what you are saying, a 5" cutout should be no problem for a 10" or larger beam (assuming 2" flanges and a 10" beam maxe size = 10"- (2x1/4"(flange clearance)) - ( 2x2"(flange size)) = 5 1/2"
The web plays a huge part in ensuring the beam stays rigid. It aids to prevent the flanges from bending.
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Old 03-19-2010, 07:47 PM   #7
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You guys answered my questions. Thank you all very much.

Tony
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Old 03-19-2010, 08:04 PM   #8
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Look for the brand stamp on the side of the joist, go to the manufacturer's site. Example- page #9: http://www.ilevel.com/literature/TJ-4000.pdf

Be safe, Gary
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Old 03-21-2010, 06:02 PM   #9
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GBR is right, the manufacturer's product guide tells you where you can cut holes and where.

Round holes are best, cut neatly with a hole saw.

It is best to locate the hole at mid height of the web although some variation is permitted.

It is best to locate the hole as far away from the supports as possible which would be at mid span. Rule of thumb is to locate holes within the middle 1/3 of the span.

If the building inspector questions it, this post probably won't do you much good. Better have the manufacturer's information.

Finally, thanks for being smart enough to ask first. Most people go ahead and cut the holes and when the building inspector stops the job (and so he should) then everyone has to scramble to get engineering, remove plumbing, ducts and wiring and repair the joists.

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Old 03-21-2010, 08:26 PM   #10
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Quote:
Originally Posted by JayKay View Post
GBR is right, the manufacturer's product guide tells you where you can cut holes and where.

Round holes are best, cut neatly with a hole saw.

It is best to locate the hole at mid height of the web although some variation is permitted.

It is best to locate the hole as far away from the supports as possible which would be at mid span. Rule of thumb is to locate holes within the middle 1/3 of the span.

If the building inspector questions it, this post probably won't do you much good. Better have the manufacturer's information.

Finally, thanks for being smart enough to ask first. Most people go ahead and cut the holes and when the building inspector stops the job (and so he should) then everyone has to scramble to get engineering, remove plumbing, ducts and wiring and repair the joists.

John aka JayKay
I'm just about posative you have the part in red reversed. the rest looks like good advice
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Old 03-21-2010, 11:19 PM   #11
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Engineered I-Beams


The part in red is correct.

At mid span, the flanges (top and bottom chords) are highly stressed and the web is not. That is why we are able to cut openings in the web here.

As we get nearer to the support, more load has to be transferred through the web and in the region of the support, the web stress is high and holes must not be cut here.

Go Here: http://www.apawood.org/ and download the publication:
Performance rated I-joists. (you will have to sign up) Refer to the hole chart on page 20. If they are not APA joists, you will have to refer to the specific joist maufacturer's product guide.

John aka JayKay
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Old 03-22-2010, 10:34 AM   #12
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Quote:
Originally Posted by tonycinque View Post
What is the maximum hole size I can cut in an engeered I-Beam? I would like to cut a hole in the web for an air duct. the literature says I can cut a hole 1/4 inch to the flange. I am talking about a single hole in two ajacent beams. Is this correct?
Thanks.
LOOK UP THE MANUFACTURERS GUIDELINES. Engineered I beams are a unique animal and most of the rules that apply to dimension lumber do not apply to this product. There are several posts here that contain information contrary to the manufacturers guidelines. You are correct about being able to cut very close to the flanges, but unlike with dimension lumber where you try to keep the penetrations away from the center, the critical areas to not penetrate on I joists are actually nearer the ends.

As suggested, it is always best to avoid square cornered cutouts. It doesn't have to be a circular penetration, but at least radius the corners to avoid stress points.

Last edited by troubleseeker; 03-22-2010 at 10:39 AM.
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Old 03-23-2010, 12:31 AM   #13
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Quote:
Originally Posted by JayKay View Post
The part in red is correct.

At mid span, the flanges (top and bottom chords) are highly stressed and the web is not. That is why we are able to cut openings in the web here.

As we get nearer to the support, more load has to be transferred through the web and in the region of the support, the web stress is high and holes must not be cut here.

Go Here: http://www.apawood.org/ and download the publication:
Performance rated I-joists. (you will have to sign up) Refer to the hole chart on page 20. If they are not APA joists, you will have to refer to the specific joist maufacturer's product guide.

John aka JayKay
I can see how this would be the case with web hung joists. is it also the case were the beams are sitting on top a loads bearing walls?
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Old 03-23-2010, 09:14 PM   #14
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Engineered I-Beams


The stress in the web is high at or near the supports regardless of how the joist is supported. But you should only support a wood I-joist under the bottom flange.
If you need to install the joists with tops flush with the top of a support beam for example, there are hangers readily available in I-joist sizes. The bottom flange of the joist sits in the hanger seat and the joist is supported under the bottom flange.
It would take some time and space to explain the structural principles of wood I-joists. Diagrams would help too. The APA documents and manufacturer's product guides explain correct usage and installation but don't explain the principles. If I can find a good reference I will post a link here.
John aka JayKay

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