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Potlight installation - drilling through ceiling joists

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  • Jan 10th, 2021 2:40 pm
[OP]
Newbie
Nov 3, 2020
8 posts

Potlight installation - drilling through ceiling joists

Hi everyone,

I'm installing potlights and wondering how the professionals can run wires across ceiling joists (between the first and second floor) without cutting extra holes in the ceiling to 1) see what's in there to make sure they aren't hitting pipes/wires and 2) bend the bit to keep it from going into the floor above?

Is it possible or do you have to cut into the ceiling for access holes?

Thanks,
9 replies
Deal Addict
User avatar
Mar 3, 2011
3688 posts
20693 upvotes
Is your second floor already finished? if so, they will wire it up the switch that is already existing. They will drill through the joists as needed it in tandem basically only drill one hole and then string the wire through the path of least resistance.

I had all my pot lights installed by https://www.qualitypotlight.ca/ A++ there's not a single bad thing I could say about them - all excellent work, I even had them licence the work for safety reasons and put on a new breaker to separate the load from a single switch.
[OP]
Newbie
Nov 3, 2020
8 posts
Yes, it is a finished house. I am trying to do it myself, I've already done most of the house, just trying to do these last couple of rooms without cutting unnecessary holes in the ceiling which requires popcorn ceiling patch up.
Sr. Member
Sep 4, 2006
939 posts
568 upvotes
Ottawa
Quite a few good how to videos on YouTube, check out the This Old House Channel for a couple.
Deal Addict
Sep 13, 2003
1279 posts
108 upvotes
Not sure anyone else has tried this before but I figured out how to use a metal hanger and shaped it like a hockey stick. The "blade" part of it was the length of half of the distance between the studs - so the end will touch the studs. Then with a stud finder, I determine the middle and then poked my hanger and swiveled it around and up/down to look for other wires and piping. I think it worked fairly well in most instances if not all. Patching up a tiny hole with some drywall compound and that's it.

I made my pot light about 4 feet distance from each other and 3 joists were the most I had to go through from end to end, a bit challenging. Bending the drill bit was a test and trial process for me, testing the depth and bend. I determined the middle of the joist by hitting the top of the 2nd floor subflooring and gradually moved it down slowly until I was comfortable that I was drilling the middle. I used another wire hanger to make it straight and used it to find the holes I made and fish the wiring, not the easiest but I was able to do it at the end.
Sr. Member
Jun 26, 2019
954 posts
706 upvotes
rohansharma636870588581785777 wrote: I'm installing potlights and wondering how the professionals can run wires across ceiling joists (between the first and second floor) without cutting extra holes in the ceiling to 1) see what's in there to make sure they aren't hitting pipes/wires and 2) bend the bit to keep it from going into the floor above?
Depending on the spacing, holes just may be required.

In regards to 1, you generally just need to figure that out based on what you can determine. There are scanners as well but most will not use it.

Some like this: https://www.homedepot.ca/product/klein- ... 1000664022

Is what most people would use to fish a bit. It does require some skill. I can get it through 2 joists pretty much straight, and I can get it through 3 joists with +/- 2 inches on the exit side. Which for a 2x8 joist is acceptable.

This said, I have seen countless people struggle to use these bits and fish wires. Like you said, I've seen lots of people when going through 2 joists go through the middle of the first one and then basically go through the subfloor above in the second one.
[OP]
Newbie
Nov 3, 2020
8 posts
SubjectivelyObjective wrote: Depending on the spacing, holes just may be required.

In regards to 1, you generally just need to figure that out based on what you can determine. There are scanners as well but most will not use it.

Some like this: https://www.homedepot.ca/product/klein- ... 1000664022

Is what most people would use to fish a bit. It does require some skill. I can get it through 2 joists pretty much straight, and I can get it through 3 joists with +/- 2 inches on the exit side. Which for a 2x8 joist is acceptable.

This said, I have seen countless people struggle to use these bits and fish wires. Like you said, I've seen lots of people when going through 2 joists go through the middle of the first one and then basically go through the subfloor above in the second one.
Any advice on how to keep it straight? You have to bend it at a certain angle to get it straight but it's difficult to make sure to keep it that way.
Sr. Member
Jun 26, 2019
954 posts
706 upvotes
rohansharma636870588581785777 wrote: Any advice on how to keep it straight? You have to bend it at a certain angle to get it straight but it's difficult to make sure to keep it that way.
Sorry, I don't have any amazing advice for you, generally speaking I bend the bit a fair bit with my hand before going into the first joist and enter the first joist smack in the middle as straight as possible. Then from there, it will probably be a learning curve a bit to figure out where you're drilling the second joist when you're blind. I just go by feel, and you can sometimes figure out where the subfloor and drywall is on either side and base it from there.

When starting out I would only do 2 joists until you get the hang of it. Once you can reliably do 2 joists, you can move up to 3.

Usually for me, going through 2 joists, I start in the middle of the first, and then the second one is off by 1 inch, with a 3rd joist I'm probably off by another inch worst case.
rohansharma636870588581785777 wrote: Is this a good video to follow?

Not really, the guy just sticks it in there and goes for it. If you did this, I'm pretty sure you'd be drilling through the bottom part of your subfloor above when you go through the second joist.
Deal Fanatic
User avatar
Oct 19, 2008
6601 posts
2182 upvotes
GTA
A tennis ball can straighten the bit, it acts as a bumper against the wall sides or ceiling. If there is a joist close to the pot light hole drill a larger hole in it than the long flexible auger bit, that way you have room to angle the auger bit so it hits the second joist at a good angle. If the first joist is well back from the pot light hole then try the tennis ball trick, there are probably You tube vids on this.

Be really careful drilling blindly into joist bays or you might install a shower in your main floor living room.

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