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Thread: DC Main Line Through TJI's.

  1. #1
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    DC Main Line Through TJI's.

    I am in the framing stages of building my shop. My dust collector will reside in the garage connected to the shop. I am thinking about running my main DC line into the shop through the rim joist and through the TJI's. I have one alignment I can use and meet the manufacturer's distance requirements. I think I can make it work for my setup.

    My ceilings will be 9', and the TJI's are 11-7/8" tall; it seems a waste not to use that space to hide some of the DC piping. The hole size would be be 6-1/2" or slightly less. There will be an office above the shop (occupied by me, so noise wouldn't necessarily be an issue). While I am not that concerned about the noise upstairs - we might turn the upstairs into an apartment at some point in the future. To that end, I am going to insulate and sheetrock the shop ceiling to separate the spaces as much as possible.

    My Questions:

    - Is it a bad idea to enclose my main line? I know this doesn't help but I haven't decided if I am going metal or plastic.
    - I am wondering about effectively sealing the penetration where the line would exit the drywall.
    - Do they make a large "donut" or something like a big grommet that would help with isolation and vibration through the joists?

    Appreciate any advice
    Regards,

    Kris

  2. #2
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    Aside from being sure you are not violating any structural rules by penetrating those joists with such large holes, the major downside to putting your duct in tight enclosure is the difficulty in making the changes you WILL make over time. Holes for wiring and plumbing are usually acceptable, but I'm not sure about something as large as you propose is acceptable. You'll need to ask the supplier of the joists or the engineer who is designing your building. My shop ceiling is made with I-joists, BTW, and I like the system.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  3. #3
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    Kris, all the I-joist manufacturers I've used have specifications as to hole sizing in the I-joist web. I don't have a chart handy but I believe your proposed 6-1/2" hole, if even allowed, will have very specific limitations as to location along the length of the joist.

    One problem with I-joists is they don't have the mass for vibration dampening like solid sawn joists. They may be stronger but there have been many complaints over the years about how the I-joists feel "bouncy". Because of that we started upsizing the joists we used to build our custom homes, either the next size wider or the same size with wider flanges. Even if you are allowed a hole that size, and even if you are able to "isolate" where your dc pipe runs through, I think upper floor occupants will feel the vibration.

    Jim also makes an excellent point about making future changes. It's not IF, it's WHEN.

  4. #4
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    Jim's comment is right on, especially regarding the size of the hole in the engineered, or even normal dimensional lumber.

    Should you decide to proceed with putting a hole in the TJI joist you need to consider not only the ratio of the diameter of the hole to the joist depth (usually a maximum of 1/3 of the depth of the joist), but also the edge distance from the hole to the joist flange; the C/L distance from the end of the joist or its vertical load bearing support; the number of holes which is dependent on the span between supports; and keeping in mind that the larger the hole dia. the more critical the concern about structural integrity. If you have to cut a large hole that exceeds safety considerations you might consider a sister joist for the affected span.
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  5. #5
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    It might be possible but I'd consult with a structural engineer about what kind of reinforcement would be possible and sufficient. Perhaps some kind of truss could be added to the web where penetrated, wood or steel.

    I built my shop with trusses, gable roof above so there was some open space. I put my 6" PVC DC (and HVAC) ducts above the ceiling through trusses (without having to cut or notch anything). It was a LOT of extra effort but I'm really glad I did it. I love that the duct work is not hanging in the shop, doesn't obstruct lighting, and can't collect dust from static.

    DC_duct_IMG_20141228_195036.jpg DC_IMG_20141228_194845_465.jpg

    I put removable access panels and clean out plugs at the ends of the longer runs, just in case. So far, no problems anywhere. Ceilings are plywood mounted with screws so they can be removed if necessary. Where penetrating the ceiling I simple cut a round hole, or ellipse where the main duct angles down to the cyclone inside a closet.

    The downside of building this way, of course, is changing the configuration would be impractical so it required careful planning of the space and equipment layout. I know people who have modified their DC layouts as their shop evolved.

    JKJ

  6. #6
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    Quote Originally Posted by Tim Bueler View Post
    Kris, all the I-joist manufacturers I've used have specifications as to hole sizing in the I-joist web. I don't have a chart handy but I believe your proposed 6-1/2" hole, if even allowed, will have very specific limitations as to location along the length of the joist.

    One problem with I-joists is they don't have the mass for vibration dampening like solid sawn joists. They may be stronger but there have been many complaints over the years about how the I-joists feel "bouncy". Because of that we started upsizing the joists we used to build our custom homes, either the next size wider or the same size with wider flanges. Even if you are allowed a hole that size, and even if you are able to "isolate" where your dc pipe runs through, I think upper floor occupants will feel the vibration.
    Here's a link to a document from Weyerhauser. See the charts on page 9 for limits on hole sizes and placement. Seems like you'll have a fair amount of flexibility with the 11-7/8" joists.

    We had a new home built ~2 years ago, and the joists under the main floor are TJIs. I believe they're 14" deep and 19" or 20" on center. All the ductwork for our HVAC runs through (and between) those joists. I want to say the holes are ~8" (we're traveling, so I can't measure).

    Tim, I'll add another complaint about the "bouncy" feel of these joists. I talked to our builder about it, and he walked me through the specs, and the design is well within what Weyerhauser recommends. But I don't think that when I'm sitting in my La-Z-Boy and my 75-pound dog walks across the floor eight feet away, I should feel the vibration (maybe I'm too sensitive). On the bright side, that vibration earned me approval from the wife to subdivide that part of the basement, which will result in a dedicated shop space - hopefully, early next year.

  7. #7
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    All. Thanks very much for the replies. I have a copy of the manufacturer's intallation guide which is what I used to identify the possibility of doing this. Having said that, I think the comments about flexibility are spot on. I am planning to surface mount my electrical for the same reason, and it is probably at least as likely the DC needs will change if not more so.

    As far as the TJI's go I did run two rows of blocking to hopefully help with the "bounce" a little.

    I will put the idea of installing the DC piping in the ceiling to rest, and focus on the dozen other things I need to get done.

    Thanks again for the input.
    Regards,

    Kris

  8. #8
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    BTW, if you choose to insulate that ceiling, please be aware that you need the "full width" material (16" not 15" and 24" not 23", depending on your spacing) because of the way I-joists are made.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  9. #9
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    That's good to know. Thank you Jim.

  10. #10
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    I mention that because many of the "big box" stores do not carry the full width fiberglass insulation material. You may need to go to a supply house or a full service lumber yard and order it. That's what I had to do.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  11. #11
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    Ditto what's already been said about the very specific hole allowances. Another issue not mentioned is that it's pretty much impossible to get a piece of pipe longer than the spacing in there if you are working perpendicular to the TJIs , so if you have 16" spacing, you have a coupler every 16". The only way to do it (that I know of) is to have a hole in line through the rim joist to feed full length sticks into. Fresh on my mind as I just helped the plumbers get a 4" drain pipe through 24' of them. Tip, if you do decide to do this, set up a laser point at the centerpoint of the hole series. Drill pilot holes no bigger than your hole saw pilot bit, starting at the first TJI, and working through the last. The laser goes through the preceding holes making a perfectly straight layout. Hole saw to fit your pipe, and you'll have perfectly lined up holes.

  12. #12
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    Just going to go with surface mount.

    Steve - I like the tip and could see other applications.
    Regards,

    Kris

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