Floor joist


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Old 11-28-07, 08:00 AM
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Floor joist

i am finishing my basement and want to run some electrical wires through the ceiling(floor joist for 1st floor). the house was built in 1947 and joist are 2x6 or 2x10's. can i drill the holes on the middle bottom or top to run the wires through?
 
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Old 11-28-07, 02:50 PM
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You should drill your holes at least 1 3/4" in from the edge. This will prevent you from driving a sheetrock screw through the wire. It will make a difference whether the joists are 2x6 or 2x10, since your hole size can increase with the larger joist. I would keep the hole size to a minimum and offset them if you have to use more than one.
 
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Old 12-03-07, 10:17 AM
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Since we have very little info

I would not drill this. You have provided little to no info on span spacing etc. All of which help in the determination of if holes can be drilled, Maybe you could attach the wires to the bottom of the joists and fur down around them instead. Maybe you have height problems and can't do that but we can't tell from the info provided.
 
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Old 12-03-07, 12:02 PM
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Code allows holes to be drilled regardless of span. Tacking the cables to the bottom of the joists and furring out is probably not a good option since they may expose the cables to nails or sheetrock screws. You can find a joist boring guide at this site.

http://www.tileyourworld.com/construction
 
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Old 12-04-07, 06:32 AM
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Yes, running wires through floor joists is common practice, even in new construction. To be on the safe side, keep the size of the hole to a minimum and drill more toward the center of the joist. This is because the center area of the joist bears less structural significance than the top or bottom. If you consider a joist under load, it bends down; this puts the top of the joist in compression and the bottom in tension. Then somewhere in the middle is a neutral axis where no compression or tension occurs. This is the principle the modern day I-joist is based on, in case you wanted to know. So in brief, drill small and in the middle!
 
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Old 01-17-08, 05:14 AM
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OK, I have a quick question to add- You say to drill thru the middle, meaning top to bottom right? What about where in the span to drill? I mean, in a 12' span, should the holes be drilled closer to one side, or in the middle of the span, at like 6'?
 
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Old 01-17-08, 05:26 AM
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Where in the span won't matter, as long as the top and bottom strength isn't compromised. I like to offset my holes to get them in different grains, but it may not matter. It's just a carpenter thing. But what can't be stressed enough is to bore minimally; and toward the middle.
 
 

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