EMT and THHN inside walls?

Started by redside, January 18, 2019, 06:27:57 PM

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redside

Was originally going to go with Romex but worried about mice/squirrels getting into walls and chewing through wires.  I don't know if I am being paranoid or not, but has anyone taken the time to install EMT to protect electrical wires inside walls? 

How would you run it?  If installed I think it would be easiest, in my situation, to notch out 3/4" inside face of my 2x6 studs to run 1/2" EMT.  I could also run it below the floor in the crawl space and up through the bottom plate where I need electrical or the top plate down; I just can't drill holes in the middle of the studs and fish the 10' sections through unless I drill through the outside corners to insert the EMT.  I suppose I could use some type of metal clad flexible cable instead of EMT, but have heard this even has problems.  Just wondering from those with experience what they would do in a seasonal use cabin? I am doing the install myself so labor costs of installation are not an issue.  I read the forums and it seems most people feel that Romex is just fine so long as a person uses spray foam to fill in any holes the Romex runs through (I read somewhere mice only eat wires to get from one stud bay to another).

Just want to make it the safest and best I can.  Honestly, I am not sure how mice and squirrels would even make it into the walls with solid bottom plates and top plates, but apparently they do and I want to be prepared.  So, EMT, Romex, AC, or other alternative??

Adam Roby

My cabin has maybe 80% armored cable.
https://www.homedepot.com/b/Electrical-Wire-Armored-Cable/N-5yc1vZc57m

The 20% that is standard Romex has been completely chewed.  So definitely if its a seasonal cabin like mine, mice will likely get and and will chew your wiring.  I would consider the armored cable before any hard metal tubing simply because it can still be pulled through studs and turn corners.  Its not cheap but it does protect the wiring.  I don't know about the legalities in different areas, maybe the experts can chime in on that aspect.


glenn kangiser

I'd go with the armoured cable too. It's so hard to get emt into the studs. I even use armoured cable externally in the underground complex. It costs a bit more than Romex, but easy to use.
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

Please put your area in your sig line so we can assist with location specific answers.

redside

Thanks for the responses thus far.....still would be interested to hear more thoughts from people.  I think this is a good thread for people in construction phase because I have seen Romex recommended lots of times and armored cable very little.  It sounds like there are people on here that have had real problems with Romex and mice.  The most negative thing I have heard regarding armored cable is 1) mice like to sharpen their teeth on it (sounds like baloney) 2) installation difficulties 3) corrosion over time. 

For a few extra buck and install time it sure doesn't make sense to have to go back and tear into the walls to replace electrical down the road. 

Another thing I heard regarding recently manufactured Romex is there is a formula for the insulation that deters rhodents from eating it.....don't know if there is any truth to this.

MountainDon

#4
Armored cable sounds easier than EMT unless you want to surface run the EMT like it is meant to be used.

As for wiring insulation that is formulated to deter rodents; I've not heard of that for Romex. However, a few years ago, in an effort to make it easier to recycle wiring from automobiles the insulation for auto wiring was reformulated. It is soy based.  Rodents love that stuff. I have no idea if Romex has changed to soy-based insulation. Maybe not as the impetus for developing it in the first place was to make it easier and more environmentally friendly when recycling a car.

Comsumer Reports has uncovered an interesting solution from Honda with regards to protecting auto wires.  However, I have not read anything about wiring being reformulated again, this time to make it less tasty to rodents.
Just because something has been done and has not failed, doesn't mean it is good design.


Don_P

An equally important part of that is to build rodent tight. Wiring is only one of a number of issues if they get in.

MountainDon

Quote from: Don_P on January 19, 2019, 01:58:19 PM
An equally important part of that is to build rodent tight. Wiring is only one of a number of issues if they get in.

Yes, excellent point.  Along with our cabin in the Jemez forest, we have a small shed and a larger shed. All separate structures, no more than 15 feet apart. The cabin was the only structure I made specific efforts to seal every crack or orifice that penetrated the shell walls, floor and roof assembly. We have never had a rodent issue with the cabin. The sheds both have had evidence of rodents at least passing through. We make use of sealed containers to keep things we want to keep safe from rodent violations. Most of the wiring in the sheds is in PVC conduit, but not all. Never, so far (knock on wood) any wiring issues in the sheds. We also don't leave food openly available to them. That may mean storing things like seeds and grains in sealed containers.
Just because something has been done and has not failed, doesn't mean it is good design.

MushCreek

Rodent tight? Good luck. My house is (so far), but the barn would be a challenge with the sliding doors. There is no food in the barn, but they come in to get out of the cold, I guess. They haven't chewed on the wiring (yet), but none of it is less than about 4' off of the slab. I also worry about them gnawing on the PEX plumbing, but at least that is shut off for the winter.
Jay

I'm not poor- I'm financially underpowered.

Don_P

My house is, the barn, sawmill and shop are not. The outbuildings have exposed framing and romex wiring, tons of mice and a few snakes and owls that follow the mice. The wiring is unchewed. (That is a code violation, exposed wiring is supposed to be in conduit to protect it from physical damage) I do have a neighbor who is afflicted with sticky finger syndrome. We were gone on a job during construction, the framing was exposed, wiring was in but the holes were not caulked yet. We came home and the crawlspace door was off, mice had gotten into the crawl and seeing light through those holes had chewed the romex insulation to make room to travel up, we ended up rewiring. The holes are now sealed and we have had no further problems, with the mice. The occasional mouse will get in through a failed door seal etc, repair and remove. You do want to build your habitation mouse tight. My biggest concern in the barn or shop is reaching into a box and coming back with a big black snake. Down in the shop I've had as many as 4 screech owls perched overhead watching me work. Generally they are after the bats but they will pick off the odd mouse.

In the commercial remodel of a 40's gas station we are replacing all the old wiring, I ran into an old cloth covered wire chewed bare last week, the mouse was trying to make it around the wire holes in the corner. Where I'm going is I believe you are just as well off spending the time and money sealing penetrations as armoring. There is of course nothing wrong with doing both.


Adam Roby

Cool owl!

I think another big factor is the "seasonal cabin" aspect.  If there is some human presence, the wildlife will be a bit less frequent.  But if you leave for the winter, there could be a few generations of mice that have never seen a human so have no fear.  I find holes where they've chewed threw walls to get in (dead center - not in a corner or anything - maybe they found some soft wood or rot).  Maybe these are just crazy mice in my area...  also the place has gone years without seeing any human presence.  I'd say if you have the time and money, do as much as you can, too much prevention won't hurt anything.

Don_P

Maybe, I think it might be more related to local pressure, material, smells... when we built around the country we would be gone for extended periods at a stretch, I think the longest run was 11 months but often 4- 6 months at a time for a dozen years. I was stacking some nice freshly sawn red oak down in the shop today, lifting the stack up to the top of the racks with the bobcat then hopping up, stickering and stacking it to air dry. An owl was in exactly that spot from the pic above the whole time, I guess we've come to an agreement. I sort of have the same agreement with the snakes that live under the floor at the sawmill, one of them is a good 7' long and I have been unstacking a pile of lumber only to find one in between layers. He rose up, we both screamed like girls, dumped off opposite sides of the pile and ran in opposite directions. Now we have agreed not to see each other if at all possible. They keep the mice down and as long as I don't find them by surprise we're good. I was working under a house one time, it was low enough under there it was impossible to roll over. I had to lay on my back and pull myself along dragging a bottle jack, some treated boards and shims. I'm not claustrophobic but was not happy. All of a sudden something was coming in out of the corner of my eye fast. Of course it was a python in my mind. My wife said the floor above was bouncing. I came out bruised just about everywhere but that poor little mouse didn't make it  :D.

On the job we're on there was a little diner in one side "Mel's Diner" what else. Termites had gotten the joists so we had the floor out. I kept sinking in old groundhog burrows yet there was a full perimeter concrete foundation with no exterior access, the hatch had been in the floor. That guy had tunneled under the footings and come back up. I assume the smells had attracted him. There is now a rat slab poured under there. We do still have mice coming in but are finding and plugging their ways in.

redside

Thanks for the real work feedback.  I will go ahead and use armored cable plus do the best job I can sealing everything up.  Looks like the armored cable is easy to run so the only negative is I have a hundred or so more in materials and supplies which is pretty cheap for peace of mind.  Sure would be nice to get some owls to hang out around the place....great picture. 

Dave Sparks

We used the screech owls  (build them a Barn owl house and the Screech will use it)  It was always a pleasure having them so close to the house during the daytime.

Since this project is probably not full time you can't use the easiest way to control rodents, outdoor cats.

The Owls so close to the house was a bit crazy some nights for sleeping....

My record for my cat Tom is 2 gophers caught at one time. d* All of my outbuildings get opened up now and then and he loves stalking. Nothing for 10+ years.

Good to see Glen back :)
"we go where the power lines don't"

Redoverfarm

Quote from: redside on January 18, 2019, 06:27:57 PM
Was originally going to go with Romex but worried about mice/squirrels getting into walls and chewing through wires.  I don't know if I am being paranoid or not, but has anyone taken the time to install EMT to protect electrical wires inside walls? 

How would you run it?  If installed I think it would be easiest, in my situation, to notch out 3/4" inside face of my 2x6 studs to run 1/2" EMT.  I could also run it below the floor in the crawl space and up through the bottom plate where I need electrical or the top plate down; I just can't drill holes in the middle of the studs and fish the 10' sections through unless I drill through the outside corners to insert the EMT.  I suppose I could use some type of metal clad flexible cable instead of EMT, but have heard this even has problems.  Just wondering from those with experience what they would do in a seasonal use cabin? I am doing the install myself so labor costs of installation are not an issue.  I read the forums and it seems most people feel that Romex is just fine so long as a person uses spray foam to fill in any holes the Romex runs through (I read somewhere mice only eat wires to get from one stud bay to another).

Just want to make it the safest and best I can.  Honestly, I am not sure how mice and squirrels would even make it into the walls with solid bottom plates and top plates, but apparently they do and I want to be prepared.  So, EMT, Romex, AC, or other alternative??

Having built a seasonal cabin I have not experienced a problem with mice working on Romex.  Their biggest point of entry to wall cavities is where the wire enters via the sill plate from a basement or crawl space.  At each one of those entry points I used steel wool filling the void around the wire.  I also used 1/4" hardware cloth (rabbit wire) stapled to the plates covering the void and steel wool.  I also used this preventive measure to the plumbing penetrations.  Generally speaking mice will not create a new entry point but use one that has already been started by some other means. 

Never had a problem with squirrels until this year.  Not really a problem yet but heard a noise the last time I was there with a friend and found a grey squirrel chewing the stain from the overhang on one corner.  A temporary fix was to staple hardware cloth over the effected area.  I will go back in the spring and try to eliminate him.  Once they gain entry into the attic area they are really hard to eradicate.