How to Run New Electrical Through Studs & Fire Block
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A good angle to use a flexible drill bit to run new electrical through studs and fire block and prevent drywall repairs on the inside.
Recently my husband and I had the “opportunity” to use a flexible drill bit. Using a 72″ flexible drill bit is a must have when you have limited options run new electrical–low voltage wire, cable line, outlet–where you don’t have the ability to fish an old line out AND YOU ALSO have studs or a fire block midway down the wall, preventing your progress. None of us want to do unnecessary drywall patches when it can easily be preempted by a tool.
As with many of our projects, we did some research, but discovered (the hard way) some of our own tips to use a flexible drill bit.
A flexible drill bit is also known as a flex shank drill bit, bell hanger drill bit, flexible installer drill bit with an auger tip. Whatever you want to call this kind of drill bit, it is a lengthy piece of steel that you attach on to the end of your drill and then attempt to hit the stud (not the drywall). When you encounter a fire block half way down the wall you generally want a 72″ drill bit to handle the distance and give you some flexiblity coming from the top or side.
Tips to Use a Flexible Drill Bit to Run New Electrical Through Studs and Fire Block
Tip #1 Wear safety gear.
Goggles are a given.
You don’t want an errant piece of fiberglass insulation or chip of stucco (or whatever exterior is on your home) to lodge itself into your eye.
Leather gloves.
Protect your hands from getting eaten up while guiding the line.
Second, the steel WILL heat up. You’ll most likely have to use both forward and reverse gears to dislodge the drill bit, after successfully drilling through the stud. The leather gloves will prevent you from getting burned.
Tip #2: Angle matters when using a flexible drill bit.
With an arc coming from the outside like this, the drill is destined to go right through the drywall.
Example of a bad angle for a 72″ flexible installer drill bit.
If it seems too easy, it is too easy.
You just went through drywall.
Make DAMN sure your flexible drill bit is right up against the exterior wall.
While some people are good at using the drill in reverse to get the drill bit right at the horizontal stud, we were a little more hesitant with the first attempt having gone very wrong.
If you go through the drywall, take the long drill bit off the drill and continue to pull the chuck end through. Don’t pull it back out the way it came. That’ll leave a big hole. By taking it all the way through, you minimize the damage and are more likely to be able to shove the drywall back into place. See Tip #5 for assistance when this happens.
On our second attempt I took off the flexible drill bit from the drill so I could shove my hand in the wall and guide it into place. It was only after the drill bit was in place that the drill was attached.
Whatever technique you use, make sure your flexible drill bit is as close to the wall as possible so you are decreasing the odds of going through the drywall side.
The second (very important–hence the bold!) benefit here is that the new low volt wire will be further from any potential nails coming through drywall for interior decorations.
This is one place where you might ask, “what about a flexible drill bit guide or a bumper balls, which keep the flexible drill bit safely away from the drywall. This is an exterior wall that had insulation in it. It was pretty hard to work in, although apparently, not hard enough to prevent the drill from walking to the other side of the wall. Plus, we didn’t have one.
Tip #3: You’ll need a hole big enough to work with.
There are a few issues here:
#1 Where are the studs?
If you happen to make a hole right next to a stud and you are limited above, you may or may not be able to get a good angle.
In all reality, it might be a bit of a crapshoot. Here at our house we were working above the ceiling inside and in a really inaccessible spot of the attic. If it was below the ceiling we wouldn’t have had a problem since we could have used a stud finder on the other side. Since we have a stucco house and there is some OSB sheathing along with metal mesh for the stucco to grab on to, the stud finder would go nuts–being totally useless.
#2 Can you get a good angle with the hole?
We had to make our hole larger so we could get the better angle mentioned in the last tip.
Space is always limited. Oftentimes overhead space is an issue. Also, the size of the hole along with the location of the studs is a limiting factor as to how you can angle the flexible drill bit. The hole above the red line is the original pilot hole where we went through the drywall.
Tip #4: Push as hard as you can horizontally so the tip of the flexible drill bit is angled down.
Apply horizontal pressure to the flexible drill bit once it is in the wall and hits the stud. The horizontal force causes the drill bit head to stand up vertical against the fire block.
The harder you push, the more likely the drill finds its way pushed into the vertical stud.
This video gives you a really good view of the inside of the wall, but notice, the drill is going against the exterior sheathing. Wood is harder than drywall, so keep the previous tip in mind when you see how easy it is on this video. I’m sure the guy in this video would have done fine in our situation and still eaten through the stud on the first try:
This tip is why I passed the drill to the muscles of this two person team.
Tip #5: Drill in short spurts.
This keeps the drill bit from heating up.
It also gives you some semblance of feedback, rather than plowing on into the drywall.
Which leads right into…
Tip #6: Have a spotter inside.
To prevent a larger mistake hole, have a second pair of eyes on the other side of the wall.
We were working under the instruction to use the drill bit in short bursts. This leaves you with a moment to ask, “Anything yet?”, hoping to hear a response such as, “No!”
You still might have to do some patching. Like we do. But maybe it won’t be as big as ours (yeah, we were both looking on the outside and no one was inside looking at the other side).
When you use a flexible drill bit it is easy to go through the drywall. VERY easy.
FYI–we watched other YouTube videos. They are the experts. But we did learn a lot from our mistakes and want to share them with you so you prevent a patch job inside when all you want to do is stucco work–not drywall!
As for Tip #2, the spotter is the assistant when it comes to pulling the drill bit out of the drywall. One person takes the drill bit off the chuck while the spotter holds and pulls the other end, rather than have the drill bit hanging in mid air while you take off the drill bit then run inside to pull the rest of the drill bit through. A second pair of hands to assist with the errant drill attempt minimizes the damage.
Tip #7. There are two very useful holes on a long flexible drill bit.
One on the tip:
Hole for where the electrical wire can be looped through the flex shank drill bit on the auger tip.
And a second hole on the chuck end of the drill bit.
Hole for where the electrical wire can be looped through the flex shank drill bit on the chuck end.
Either can be used to hook the cable and pull it through.
If you can’t reach the drill bit, then you’ll use tip #8, #9 and #10…with a glow stick set (aka fiberglass cable wire running rod connectable fish tape pull kit) like this one.
And, heh, those two photos look like one of those activity book pages where you find three things that are different… #1 being that this actually is showing two different ends of the same auger tip flex drill bit!
Tip #8: The fiberglass glow stick will probably need to be longer than the flexible drill bit.
Your target hole is below the stud and you still need some space to attach the wire along with enough to grab onto to pull the fiberglass glow stick back up.
Electrical tape over the new wire looped through the bullet nose attachment on the glow stick.
Expect to use two (if you have the 54” sticks like we did).
The two daisy chained glow sticks extending out of the hole in the stucco.
Tip #9: You’ll need a bullet nose attachment to run new electrical through studs or fire block with fiberglass glow sticks.
The cord needs some way of attaching to the glow stick.
Most sets come with one.
Tip #10: Pay attention to which end of the glow stick extends to the line you want to fish.
The two daisy chained glow sticks are running through the wall, peeking out of the new doorbell location with a bullet nose attachment and extending out over the top of the entryway.
We did this backwards the first time.
The good news is, once you find the hole the first time, the second time is much faster!
Fishing for the glow stick in a wall filled with insulation with some hooks is still a PITA, but it is also faster too!
The side with the threads should go towards the electrical cord to draw it back inside with the bullet nose attachment. Perhaps you should put the bullet head attachment on there first as a reminder.
Considering how many things went wrong with this doorbell install, we weren’t about to put it on before. Even if we had glued it on, it probably would have magically fallen off in the wall.
So once the glow stick was sticking out we twisted on the bullet nose attachment and pulled it out further with one of the hooks.
Tip #11: The auger tip flex bit needs to be wider than the mechanism used to fish the wire.
The auger tip extended drill bit should be larger than the fishing line (glow stick), new electrical wire hooked onto the bullet nose drill bit, along with some electrical tape to ensure it stays in place while it is pulled through stud or fire break.
This is what is beneath the electrical tape in the last photo: a loop of the new low voltage 20-2 wire through the bullet nose attachment on the glow stick.
If the hole is too small the glow stick and the electrical wire hooked through the bullet nose attachment won’t make it through.
Maybe you can use one of the ends of the drill bit and this is a non issue.
For the rest of us who have to use glow sticks the electrical wire hook on the bullet nose attachment is the limiting factor.
I like the set I mentioned above more than the set you see in the pictures because the bullet nose is thinner so the hook is not as wide. In addition, the connectable sections are smaller than over four feet so the length is more manageable as you see there was almost a full stick poking out of the top of the wall. This is better for when you have less space for pulling above the hole.
Tip #12: Did I just make a hole in fire block? Isn’t it supposed to be sealed?
Yes, you are supposed to put fire blocking sealant or foam where you cut the fire block, but did you want to run the line through or not?
In the process, we discovered this has got to be a replacement door and window set. If a doorbell wire goes down and around a window instead of up, the door jamb is questionably held in place by…well, we question what, and we know the electrical line going to the refrigerator also powers the only outlet in the garage and the outlets for the kitchen… a single hole in the fireblock of this house is not going to save anything.
Our answer?
Prayer.
Tomorrow’s YouTube video highlights some of these tips:
Flexible drill bits are one of those esoteric tools you rarely use, but are really necessary when you need them. Whether you choose a flex shank drill bit, bell hanger drill bit, flexible installer drill bit with an auger tip you should now have a better idea of how your own job will go. You may or may not need a fiberglass glow stick pull kit as well.
Keep these tips in mind to maintain your sanity and REMEMBER TO KEEP THE ANGLE AS CLOSE TO THE WALL AS POSSIBLE!
Do you have any additional tips to run new electrical through studs or fire block using a flexible drill bit? Please add them to the comments below!
Here is the backstory on why we had the “opportunity” to use the flexible drill bit in the first place…
This was not our first choice.
Unfortunately, the line we intended to fish to upgrade the 20 gauge telephone wire to 18-2 thermostat wire snapped at the top of the wall, rendering the old wire useless for fishing.
Option #2 could have been patching the interior drywall, but it was not clear where it should be. Second, patching orange peel texture is difficult to blend in seamlessly unless it is something you do for a living.
We don’t.
Since I live inside my home and when I’m there I spend 90% of the time inside (10% spraying rocks for weeds, coming up with some amazing chalk drawings, and smoking pork butts with a brew in hand), I’m more likely to notice a patch in the ceiling and/or wall.
So outside stucco it was.
I already stuccoed the entire outside of the house from skip trowel to smooth, so I could probably do a decent enough job way up high. Most people peep in through the window, no longer look at my front door covered with peeling paint in horror, or munch on the basil growing along the entrance as they wait. They aren’t going to look up at the stucco patch way above their heads.
This photo pretty well sums up the destruction:
The aftermath of pulling new wire: A missing door trim piece because the old doorbell wire would not budge. Having to remove the security door because it prevented taking off said door trim. A larger hole in the stucco once the old wire broke in an extremely inconvenient location, taking off the plywood siding we had already sealed with spray foam while we were still looking for the old wire. It was a cluster.
