Almost every home and apartment complex in the US is wired with NM cable.

Any particular reason you are considering MC (metal clad) cable?

Installing MC cable will cost more, and unless you have experience installing it, it may take longer to install.

Create a material list for both installations then decide.

Boxes and box connectors are different.

 

Without code dictating its use, I would not even be considering MC. NM gets my vote.

 

In the walls behind a finish or just drilled in the studs?

 

He said "as protection behind walls?"

 

Type MC or AC cable has the same protection requirements as NM.

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If you need critter proofing and will have open walls, I'd use MC.
If you will cover the walls, NM will do fine. Just don't leave any open / large holes or gaps that mice can get into.

With six months of winter, living in the woods, and seeing small rodents move into sheds, garages and homes - and they like to chew on wire cabling - I used MC for my open stud wall multi purpose shed / shop and wood storage shed. Backed up by a few mouse bait blocks, to minimize damage to any other materials and tools that may be stored. Both easy and cheap insurance against having to deal with rodent damage.

 

I too am building a detached garage . It will have a 20x24 work shop and 16x24 garage for parking my tractor and bike.

I am a Licensed Electrical Contractor going on 25 years and I am using NM.

Someboy above said if you think you will have rodents you might consider MC. I agree with that.

 

I've built a few shops over the years and every one of them has had NM cable behind sheetrock, plywood or OSB and it has always worked fine with one exception. It's more difficult to upgrade or change. Mostly when I need to add a machine, to move the layout around for a change in workflow or to make room for the piece of equipment. My current shop still has some cable in the walls but now I'm using EMT conduit mounted to the surface of the walls.

It's easy to work with and makes changes a lot easier. I use stranded THHN wire as it's easier to work with. If you use the right fittings the conduit can act as the ground but I usually pull in a green ground wire anyway. All my receptacles or switches are in deeper 4x4 boxes. The boxes are all the same but can be configured with different face plates to house single or double receptacles/switches or 240v receptacles as well.

I kinda like the industrial look of it. I bought a couple benders for 1/2 and 3/4, also a "little kicker" to bend the offsets quick and easy. Can be done with the regular bender as well, just a little more work.

 

Given the way things constantly change in a wood shop as you get new and different tools, iamrfixit has the right idea.

The other neat thing EMT does for you is allow you to NOT buy wires right now when prices and supply chain are bonkers.

With NM (or MC or any cable) behind drywall, you will need to pre-anticipate every possible setup you will ever have, embed the wires in the wall for that, pay for those wires now, and hope you didn't forget anything, and/or give a pass on bargain tools because you don't have the power in the walls for them. For instance if you decide to go 3-phase with one phase converter feeding multiple machines, you will need to bust drywall to put in /3 or /4 cable. Joe Conduit just pulls in another THHN wire.

 

I agree with Harper and others above on EMT as I am an industrial guy, but I also realize some guys want behind wall wiring.

I will say this as someone that is wiring up a shop currently. I demanded MC cable IN the walls! Why? Because it is cheap insurance against rodents! Will it happen? Who knows, but with MC and steel boxes, I don't have to worry about anything.

MC is super common in commercial office buildouts with steel studs because NM is easy to tear up in that application. There might be grommets for use NM for that, but we used nothing but MC in office spaces, and EMT/rigid in shop areas.

Another selling point with EMT is that is accepted as your ground path (no ground wire). You also can pull some nice stranded THHN wire and once you go stranded, you don't go back...lol

 

I agree with Harper and others above on EMT as I am an industrial guy, but I also realize some guys want behind wall wiring.

It's totally possible to install EMT inside a framed wall. You just have to like couplers You center-drill the 2x4s, make sure the holes line up straight. Drill the hole a bit large and see how much EMT you can angle in through the hole. Will be < the width of 2 studs but that's fine. Saw-cut, ream, coupler, lather, rinse, repeat.

My vote is EMT as well. But this will require bending skills. Its not hard and a few bends you learn may be all you need.

You don't need much bending skills. The key is don't attempt compound bends, use couplers to connect simple bends. And feel free to leave ends a little long so they overlap, and then just cut to fit.

 

My vote is EMT as well. But this will require bending skills. Its not hard and a few bends you learn may be all you need. It does not have to look perfect either as it will be covered up.
Unlike others, I always pull a ground in each conduit. Using the conduit as your ground is a compliant install. But separated conduit at fittings is not uncommon. This happens, your ground is gone.
Of course you have to buy the extra wire. To me it just makes more sense.
Remember you will use THHN/THWN single conductors. And last time I checked it is not cheap. But worth it in the end. IMHO.

 

Going up and over or down and under avoids the need for all the couplings

 

You know Jim I, learned that from a master when I was a very young journeyman.
We went to a small office build. It was in the plant. Just a structure assembled inside with roof and walls.
We did not make one hole for horizontal runs. We bent tall 90's all on the floor. Set them into couplings from the top, swung them together, cut and coupled. We were in and out of that job in a couple hours.
On the way back I asked him about all the conduit and wire we used. His response was the time made more sense than the material.
I never forgot that. Its smart, uses more material, buts fast as heck.

 

Metallic Flex Conduit can be drilled through studs (same as NM and MC). Because it's conduit it can be easily changed to anything you want by just pulling in new wires.