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Thread: 3/4 Inch Wholes in Floor Joists

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    DIY Senior Member seaneys's Avatar
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    Default 3/4 Inch Wholes in Floor Joists

    Hello,

    I'm putting in radiant heating (pex). I'll need to drill 3/4 inch wholes in the floor joists (2x12). The floor joists are in the new addition to our home.

    I understand that I need to place the 3/4 inch wholes in the center of the joists and that I should avoid the middle 1/3 of the joists.

    In a few places I will need to drill a series of wholes to accommodate different zones / different runs of tubing. What are the guidelines for drilling a series of wholes that are side by side in floor joists? Should I space them a few inches apart? Should I stagger them off of center slightly?

    Thanks,
    Steve

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    Retired Defense Industry Engineer jadnashua's Avatar
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    If you are using 1/2" pex, I'd use a bigger hole! The OD of 1/2" pex is 5/8", and I can tell you from experience, you'll quickly find it very difficult to pull pipe through. For that size hole, I'm not sure it makes that big a difference along the length of the joists. if it was a bigger hole, then I'd be worried. Wait for one of the pros.
    Jim DeBruycker
    Important note - I'm not a pro
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    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by seaneys View Post
    I understand that I need to place the 3/4 inch wholes in the center of the joists and that I should avoid the middle 1/3 of the joists.
    Not necessarily, as all of that is at least somewhat relative to the sizes and numbers of holes. I-joists commonly come with centered knockouts spanning their entire lengths. Nevertheless, I would still try to stay near the vertical centers of the joists, and your layouts will likely keep you near the ends.

    Quote Originally Posted by seaneys View Post
    In a few places I will need to drill a series of wholes to accommodate different zones / different runs of tubing. What are the guidelines for drilling a series of wholes that are side by side in floor joists? Should I space them a few inches apart? Should I stagger them off of center slightly?
    Three or four inches apart and alternately staggered an inch or two above and below center would keep things tidy without lining them all up or causing weak spots.

    Here are a couple of pictures I found somewhere, and a web search for something like "install radiant" should lead to plenty more.
    Attached Images Attached Images   

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    Plumber jimbo's Avatar
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    Not trying to get the forum too politcal here, but I absolutely agree with JAD's comment about SSN's. Too many people already have my SSN, and that scares me, but the dentist, the phone company, etc etc do not need it. I am not asking any of them to extend credit. If they must do a credit check, you name is enough! I just decline to provide it, and so far no one has refused to do business with me, although they could if the wanted to.

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    Jack of all trades frenchie's Avatar
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    Quote Originally Posted by seaneys View Post
    Hello,

    I'm putting in radiant heating (pex). I'll need to drill 3/4 inch wholes in the floor joists (2x12). The floor joists are in the new addition to our home.

    I understand that I need to place the 3/4 inch wholes in the center of the joists and that I should avoid the middle 1/3 of the joists.

    In a few places I will need to drill a series of wholes to accommodate different zones / different runs of tubing. What are the guidelines for drilling a series of wholes that are side by side in floor joists? Should I space them a few inches apart? Should I stagger them off of center slightly?

    Thanks,
    Steve
    You only have to avoid the middle 1/3rd of the span for notches. Where you've cut into the top or bottom edge of the joist.

    If your holes are in/near the center of the joist depth... at least 2" away from the top or bottom edge is the code spec... you can make your hole anywhere along the span. Even the very middle.


    Leave at least 2" of solid wood between any holes.


    ...interesting. My code book is totally silent on the maximum allowable number of holes you can make in a joist.


    ...this is from an old thread, here; the drawings on page 2 disambiguate things nicely:

    http://www.tileyourworld.com/constru...oringGuide.pdf
    Master Plumber Mark:

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    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by jadnashua View Post
    The only thing your SSN should be given out to is the government and someone who is trying to give you credit ...
    Why to the government? There is no need for any of us to be numbered.

    Quote Originally Posted by jimbo View Post
    I just decline to provide it, and so far no one has refused to do business with me, although they could if the wanted to.
    I was refused a random drug screen until the clinic called my employer and got it anyway.

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