ECN Forum Forums Code Related Discussion Building Codes for Electricians Floor Joists

This is an E-mail I recieved this morning from a gentleman.

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Ryan,

Can I drill 4.125” holes through the ‘I-Beam’ floor joists (not cutting the 2x2 part, just the web) to get the duct work to the outside of the house for a bathroom fan? I need to drill through three (3) of them near the foundation wall.

John Doe

Senior Sales Manager

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How would you answer this question?

[This message has been edited by Ryan_J (edited 10-31-2003).]

Call the manufacturer. They have the engineering info on something like that.

Ryan,

I think Scott's is the only answer possible.

Bill

What can you do without consulting the manufacturer?

I've seen holes for 8" round ducts that didn't create a problem.

Ryan,

If he's not talking about a wood beam I think the only safe answer is to consult the Manufacturer. From what I've learned about engineered beams they are manufactured with different material/characteristics in different places, simply put some parts are stronger than others.

Bill

He's talking about I-beam floor joists, ie. TJIs (from Trus Joist), BCIs (from Boise Cascade), LPIs (from Louisiana-Pacific), etc. Any lumber store that sells them should be able to provide you with an installation guide/flyer that has a hole chart showing what size and where holes many be drilled. Just be sure the hole chart is published by the manufacturer of the particular joists you are drilling. I try to keep one from each of the manufacturers in my office so that I can refer to the correct one.

I call them 'micro-lam' beams.
Do they have pre-pressed 'knockout' holes for plumbers and electricians?


Here is a similar link about trusses.
Truss Discussion

(edited to shorten URL)

[This message has been edited by Webmaster (edited 10-31-2003).]

This is the answer that I gave the gentleman:
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Mr. Doe,

It depends greatly upon where the holes are located in relation to the span. As a rule of thumb with I-joists, you want to stay towards the center of the span for large holes. I have seen holes that would accommodate an 8” round duct through the middle of the span without any problem. If you can, try to stay within the center 1/3 of the span. If you are drilling “near the foundation wall”, you may have a problem. If I were inspecting the job, I would ask for the manufacturer of the product to provide approval.



In my neck of the woods, the suppliers of these products are very helpful to provide this information free of cost. I would consider contacting the supplier (not necessarily the manufacturer) and get their advice.



I’m sorry I don’t have a better answer for you, but the rules for I-joists are not set in stone. They are different depending upon the manufacturer and other variables, such as span, spacing and sizing.

Hope this helps you, Ryan Jackson

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Great answers guys! That is exactly the way I view it. I think there is a fine line between helping someone with a question and praticing unlicensed engineering...I'm not willing to cross that line and glad you guys aren't either.

I know it's late, but down here, most AHJ's will red tag ANY cut micro-lam beam (AKA glue-lam). The TJI 'I' beams (the ones with particle board (OSB) in the middle and 2x2's on the top and bottom have a lot more leeway for access holes. Most Lam beams have to be special ordered with access holes, IIRC.

[This message has been edited by DougW (edited 01-08-2004).]

Doug: I also red-tag modifications to engineered lumber. It seems as though they are pretty forgiving, about 90% of the time the engineer will crunch numbers and come back to say that everything is fine...