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...

The International Residential Code, section R502.8.2 forbids such acts:

"Cuts, notches and holes bored in trusses, laminated veneer lumber, glue-laminated members or I-joists are not permitted unless the effects of such penetrations are specifically considered in the design of the lumber."

To me this would mean engineering approval. Many I-joists have K-Os in the approved areas. All engineered lumber comes with literature that should be consulted when cuts are considered.

A general rule of thumb out here for cutting holes in joists is that they must not be cut in the center 1/3 of the member, but in the outer 1/3, the closer to the point of support the better.
I think that I'd want engineering. At least if they "crunch" the numbers, I'd not be accountable if the joist "crunched"

Electure: Your description is great, if you are dealing with sawn lumber (2X10, 2X8, 2x12, etc.), if you are dealing with engineered lumber, such as I-joists, it is exactly the opposite. As strange as it sounds, it is much better to drill an 8" hole right in the middle than to drill a three inch hole a foot away from th ebearing support. I know it sounds strange, but thats what the guidelines that come with the products state. It is also waht the engineer's will tell you.

Ryan,
Thanks.
I didn't know this.
We've been doing the TJI joists, apparently, incorrectly.
(best laid plans of mice & men)
I'll want a cut sheet before I do another.

[This message has been edited by electure (edited 01-16-2004).]

On the topic of being a pseudo engineer, I agree that the libility can be severe if one takes it upon themselves to "engineer" a portion or all of a project without the appropriate credentials.

Not withstanding, it is important to know where to get the best engineering possible. Go to the manufacturer to get the best possible data on questions and/or products that present a solution to an engineering problem at hand.

With that in mind, engineered floor and roof joists are becoming the replacement for dimensional wood products.

The question of "holes" and where can they be cut is not frivolous. The structural integrity of a floor or roof can be destroyed with the inappropriate installation of air ducts, plumbing and electrical lines.

I have found the folowing information re: holes, on page 24 and 25 of the JAGER US Residential manual very informative.
http://www.jagerbuildingsystems.com/pdfs/guides/USA/us_residential.pdf

For the ultimate flexability the "Space Joist" design with open web integral with an upper and lower Chord is the best system that I have found to date. There is a premium to pay for the joist but when the trades are considered, the overall capital costs are lower.

For anyone interested, JAGER also provide software to assist the project manager or residential contractor test various products and their design capabilities. I have had great success in knowing what I want before I contact the truss manufaturer. Good to be aware of the alternates for competitive quotations as well.

Doug.....et al (who is this al anyway?)


[This message has been edited by DGT (edited 01-16-2004).]

Not to be a pain about this but here is the site for the "Space Joist"
http://www.jagerbuildingsystems.com/english/products.htm

Up, up and away......

Doug......et al