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RUNNING CONDUIT in a wood frame house SIX BY NINE?! I decided to run conduit for electrical-supply and signal cabling while the walls are down at Grey 17. A housemate and I recently opened up the basement ceiling (which had been drywalled, taped and painted for some reason) and discovered a problem. The joists under the non-load-bearing walls are 6"x9" beams.[*] That's huge! I guess I can drill through that vertically upward, but not downward. (How would I clear 9" of wood shavings? Even 4" can be a challenge.) [*]: They seem to vary in width from 5.5" to 6". I'd like to run two electrical circuits, 6 cat5 cables, and at least 2 video coax cables upstairs in one area. The signal cabling (cat5 and coax) I want in the same gap between studs. Even if I split that into two conduits, can I fit all that in one area? If I use a huge conduit size, I'll weaken the joist too much. I guess two or three small conduits in a row (grain-wise in the joist) wouldn't be too bad, since the joists are loaded from above, not from the side. Comments? Suggestions? --David Krikorian Hmmm... I'm guessing this is an old post-and-beam house, right? That's the only thing that would explain varying-width joists that size... That said: are you *certain* that you have a joist *directly* in line with the full length of the wall? If the wall hangs over the edge of the joist by as little as an inch, that's enough space to run your lines up into it at an angle alongside the joist rather than through it. *IN GENERAL*, if you find yourself having to drill through huge amounts of wood to run utilities, you're doing wrong. The annals of renovation are *full* of cases where someone drilled all the way vertically through a 2x12 joist ("gee, it's taking a long time and making LOTS of shavings!"), when they could have painlessly moved the line two inches over and not had to drill through anything. It's really horrifying to open up your wall and find that a previous happy-homeowner had done just that... Your case *MAY* be one of the exceptions. If you do find yourself having to drill vertically through the joist, what I would do would be to "sister" the joist first. Nail a 3-foot length of 2x8 to either side of the joist where you're going to drill your holes:
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That's huge! Sister the joists anyway, just to be on the safe side. Also: you'll HAVE to use at least two conduits here: code forbids running power and communications wires in the same conduit... What kind of conduit did you plan to use anyway? --Jim Paradis > I guess two or three small conduits in a row (grain-wise in the joist) wouldn't be too bad Separate the holes by 3+ diameters to minimize weakening. > the joists are loaded from above, not from the side. Beam stress is largest on the top and bottom surfaces. Picture an I-beam; extra material where the stresses are worst. Holes through the "side", perpendicular to load force in the middle of the beam, would have the least impact. You may also be able to drill diagonally, in the side and out the top, presuming you can handle a bend there. HD sells flexible blue plastic conduit, about 1" O.D. that's good for this kind of stuff. -dca "Smurf tubing" is the technical name. Amateurs call it ENT (Electrical Non-metallic Tubing). It comes in different diameters, although it sounds like, from what you already want to put through it, you'll want the 1" diameter. --russ nelson |
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