I'll be newly wiring a room on the second floor, in this case putting in outlets. The house is old, balloon frame 2x4s, with a double 2×4 top plate that the rafters rest on.
I have 250 feet of 12/2 mc cable that I was going to use to do the electrical that I got from a friend for free.
I am presently planning on running the cable along the rafter ties, down the rafter, through the top plate, and then back up and along to the next outlet. This means two holes in the top plate per outlet.
I'm just a bit uncertain about drilling through the double top plate. These are true 2x4s, but even so, the mc cable has an exterior diameter of around half an inch. That means 5/8 or 3/4 holes. Do two holes of either size present structural concerns that warrant a reinforcement of some kind? I know for notches in the top plate(s), you need to put steel reinforcement on, however I can't find a clear answer with holes of this size. Is there an optimum place to put the holes? In the middle, equidistant from eachother and from the studs?
Any assistance(or general advice) would be welcomed.
Best Answer
I would be placing a junction box in the attic and only running 1 line down to each receptacle.
Running up and down is a waste of wire and if the walls are not open a lot more work fishing metal clad can be a pain in the back side especially if there is insulation. Having a 4x4 box makes a great junction box get a deep box with all 1/2 or 1/2 -3/4 TKO and you will only need 1 box for most rooms.
When I usually do this I many times add a raised single duplex cover and add a convince outlet it can be handy to have if there are no outlets up there.
With balloon framing you need to reduce the amount of damage (drilling) I don’t work with balloon as often as it is somewhat rare but you need to be aware additional holes will compromise the structure.
Make sure to use the insulating bushings that came with the MC inspectors look for this if your roll doesn't have a bag get some they are only a couple of $ for 50 or 100 I cant remember how small the bags come.