Running wiring in a garage ceiling joists.

Rebelguy · Aug 9, 2020

Hey folks,

I had a couple of questions regarding running electrical cables in an attached garage. Any help is appreciated.

#1. I am installing a recessed sub-panel in my attached garage. I will be running 2-2-2-4 cable from the main panel to the garage through my attic crawl space. The cable will pass through sheet rock when entering the garage. Here is where I needed some assistance. I am planning to run the cable about 4 feet on the roofline and then drop into the wall so that I can tie into the box from the top. This is a cathedral style roof and the area where the wire will be run is about 12 feet off the ground. Should I use wire straps to attach to the joists or drill holes in the joist to support the cable?

#2. When the service cable enters the wall does it have to be in conduit for protection or is strapping it to the stud until entering the panel enough?

#3. I am going to be closed foam insulating the walls. Can the service cable be covered with the closed foam?

#4. I am running romex for ceiling mounted electrical outlets. A couple of the runs would be a lot easier to run along the top of the wall where the ceiling and walls meet. Is this okay to do? Is it okay to drill a 1/2” hole in the joists in this area to run the cables though?

#5 Metal or plastic Boxes for ceiling mounted outlets?

I have attached a picture of the joist area for the service cable question. I have also attached a picture of the wall cavity where the service cable will be run in. Lastly there is a also a picture of the top of the wall area where I am running romex.

Thanks in advance for any help.

Regards,

joesparky · Aug 9, 2020

that cable is technically supposed to be strapped every 54 inches (5'6") once youre in the air. Clearly you can do that. Run it atop the beams. On the other hand, if you feel that you will slide things on the rafters , protect it by drilling it through the rafters. You dont HAVE to though.

2. no it doesnt.

3. yes.

4. yes.

5. plastic. However if you use metal (im pro pipe in everything) the box will be far more sturdy. You will require NM connectors though (nm is "non Metalic". they almost look like BX connectors)
if you can mount a box using the rafter, do so, or make a cross member to support the box, or use a box mounting bracket.

regarding where you run, if youre putting up drywall, you have no option but to run it in such a way where its not going to be damaged by nales and such.

for example, when passing through a beam or stud, it has to be in the center of it. Not right on the edge..And most certainly not where the drywall is pressed against it because you ran the wire on top of the face of the wood.

an easy way to look at it would be, What if it were made out of glass, and you were connecting glass rods?

You wouldnt set it where there is an easy way to damage it, right? treat your wire the same.

However, the wire youre running has protection.

If you can run a PVC down the insulated wall? it wont do anything but make life easier to service it later. run it big. a 3/4 pipe if you do.

I despise people running Romex in a conduit, but people do it.

Megawatt · Aug 14, 2020

joesparky said:
that cable is technically supposed to be strapped every 54 inches (5'6") once youre in the air. Clearly you can do that. Run it atop the beams. On the other hand, if you feel that you will slide things on the rafters , protect it by drilling it through the rafters. You dont HAVE to though.

2. no it doesnt.

3. yes.

4. yes.

5. plastic. However if you use metal (im pro pipe in everything) the box will be far more sturdy. You will require NM connectors though (nm is "non Metalic". they almost look like BX connectors)
if you can mount a box using the rafter, do so, or make a cross member to support the box, or use a box mounting bracket.

regarding where you run, if youre putting up drywall, you have no option but to run it in such a way where its not going to be damaged by nales and such.

for example, when passing through a beam or stud, it has to be in the center of it. Not right on the edge..And most certainly not where the drywall is pressed against it because you ran the wire on top of the face of the wood.

an easy way to look at it would be, What if it were made out of glass, and you were connecting glass rods?

You wouldnt set it where there is an easy way to damage it, right? treat your wire the same.

However, the wire youre running has protection.

If you can run a PVC down the insulated wall? it wont do anything but make life easier to service it later. run it big. a 3/4 pipe if you do.

I despise people running Romex in a conduit, but people do it.

Joe at times I run romex in 3/4 PVC sometimes especially if it’s exposed. As long it is strapped effectively it makes a much better Looking application and also give a following electrician a route let’s say under the house without drilling a hole.

joesparky · Aug 15, 2020

Megawatt said:
Joe at times I run romex in 3/4 PVC sometimes especially if it’s exposed. As long it is strapped effectively it makes a much better Looking application and also give a following electrician a route let’s say under the house without drilling a hole.

thats why I said "but people do it"