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Running cables through joists / insulation over ceiling boxes

Running cables through joists / insulation over ceiling boxes

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  #1  
Old 11-29-05, 10:01 AM
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Running cables through joists / insulation over ceiling boxes

I recently bought an old house (~100yrs old). The basement is unfinished, with all the wiring from the electical box running across the basement ceiling, stapled to the underside of the bare joists. I want to add a drywall ceiling to the basement, screwed directly to the joists to maintain height. So I need to "lift" the cables up and out of the way. The best way I figure I can do this is to bore a hole in each joist and run the cables through the holes. Question is, if the joists are 8" tall by 2" wide, what is the maximum size of the hole I should bore? I estimate that a single 2" hole would be sufficient to hold all the cables (with some room to spare). Or is it better to drill multiple smaller holes?

Additionally, I noticed in the attic that the some of the ceiling boxes holding light fixtures in the rooms below are covered with insulation, some are not. I know that recessed lighting should not be covered (unless IC rated), but couldn't find any literature specifically on normal ceiling boxes. Can anyone tell me whether it's okay to cover ceiling boxes holding light fixtures and fire alarms in the rooms below? Thanks!
 
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  #2  
Old 11-29-05, 10:08 AM
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Originally Posted by mooserus
Can anyone tell me whether it's okay to cover ceiling boxes holding light fixtures and fire alarms in the rooms below? Thanks!
It's perfectly fine and quite normal.
 
  #3  
Old 11-29-05, 10:11 AM
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Drill the holes dead center (top to bottom). Smaller holes spaced at least 3 inches apart are better than larger holes. Drill perhaps 3/4" holes and run two or three cables through each hole. Because of possible overheating of the wires, never run more than four cables through the same series of holes. If possible, stay out of the center third of the span, and don't get within a couple feet of a supported end.

If the cable is more than 20 years old, take this opportunity to replace it with new cable. Don't bury any junction boxes behind the drywall.

It's okay to cover electrical boxes with insulation in the attic. It's not okay, however, to cover knob-and-tube wiring (if you house is that old).
 
  #4  
Old 11-29-05, 11:43 AM
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Wavy Ceiling

With a 100 year old house, you can rest assured that the bottom of the floor joist where you want to attach the sheetrock are not level.

It may be best to put furring strips on the bottom of the floor joits, not only to have a level ceiling, but to ensure the edge joints fall on a surface that you can nail or screw the drywall to. 100 year old floor joists are mighty hard and nailing or screwing into them will quickly turn into a frustrating task. This also reduces the need to move the wires, unless as John suggests their age requires replacement.

The furring strips will only reduce the finished ceiling height by 3/4".
 
  #5  
Old 11-29-05, 12:02 PM
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Originally Posted by sgtgerryf
It may be best to put furring strips on the bottom of the floor joits, not only to have a level ceiling, but to ensure the edge joints fall on a surface that you can nail or screw the drywall to....The furring strips will only reduce the finished ceiling height by 3/4".
I thought of this, too, but I will add a warning. Put some kind of protection, like a metal strip across the furring where the wires are. They will be too close to the drywall and would be sure to get a screw during installation or at some time in the future.
 
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Old 11-29-05, 12:02 PM
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Originally Posted by sgtgerryf
With a 100 year old house, you can rest assured that the bottom of the floor joist where you want to attach the sheetrock are not level.

It may be best to put furring strips on the bottom of the floor joits, not only to have a level ceiling, but to ensure the edge joints fall on a surface that you can nail or screw the drywall to. 100 year old floor joists are mighty hard and nailing or screwing into them will quickly turn into a frustrating task. This also reduces the need to move the wires, unless as John suggests their age requires replacement.

The furring strips will only reduce the finished ceiling height by 3/4".
These directions will create a very unsafe situation indeed. The wires would be too close to the inside surface of the wall, and would require nail plates to prevent a nail or screw from being placed through the wire.

While furring strips may very well be needed to make the ceiling level, there is still the need to move the wires so that they go through the joists.
 
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Old 11-29-05, 12:30 PM
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Misunderstood directions

Perhaps a clarification is in order.

The furring strips would run perpendicular to the joists, just like the wiring does. The wiring would then be between two furring strips , one on each side, spaced away from the wire to avoid an accidental penetration. If need be, the wires should be able to be moved slightly from their current location to keep the furring strips at 16"OC.

Running a furring strip in the same direction as the floor joist doesn't accomplish anything, because it doesn't give you the ability to level the ceiling from joist to joist.

Hopefully this clarification helps.
 
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Old 11-29-05, 12:33 PM
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Same issue. Plate needed between ceiling sheetrock and cable where cable passes over joist.
 
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Old 11-29-05, 12:46 PM
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No Problem

No problem with the "nailing plate" being installed over the wires as it is code and I'm all for that as well as safety, I'm just looking at this project from the homeowner's perspective. To move all of these wires vs. furring out the ceiling seems to me to lean to furring out the ceiling.

With the nailing plate and furring out the ceiling the homeowner ends up with a safe installation, a quicker completion time (in my opinion) and a flat ceiling.

Of course, the final decision is up to the homeowner if he feels more comfortable doing more electrical work and less carpentry or more carpentry work and less electric.
 
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Old 11-29-05, 12:57 PM
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Originally Posted by sgtgerryf
Running a furring strip in the same direction as the floor joist doesn't accomplish anything, because it doesn't give you the ability to level the ceiling from joist to joist.
Furring for flattening purposes with strips of cardboard (not corrugated) along joists or studs is common practice.

This can be done in conjuction with the wood for spacing purposes and is what I was picturing.
 
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Old 12-10-05, 12:29 PM
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Next question!

Thanks for the replies so far. The basement project seems to be going well to date. Next issue I have run into is that obviously as I'm lifting the wires up and running through the holes, I'm finding that some don't reach the main panel anymore - usually by 6" (typical!). Instead of running entirely new cable throughout the house, is there any issue if I use a junction box and 2' of new cable to complete each run into the main panel?
If I have to fit ~4 junction boxes, rather than have the boxes all sticking through holes in the new ceiling I was going to install, would there be any issue if I place the junction boxes above a ceiling panel, but actually use a hinge and handle on the ceiling panel so that it can swing open and shut to allow access to the junction boxes?
Thank you for all your advice so far - it's been invaluable.
 
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Old 12-10-05, 09:52 PM
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Sounds fine. You can find plastic "access panels" in various sizes at your home center which snap onto drywall.
 
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