Spray foam... before or after wiring?

[jaw22w]

I am doing the interior of my new 30x40x12 pole barn. The next step is wiring or spray foam. I am doing the wiring, and the foam will be hired out. I am only getting 1-1/2" closed cell foam on the walls only. That will seal up the building. Then use R-19 fiberglass to finish. Walls will be covered with OSB on horizontal girts on the interior face of the poles. The ceiling will be white liner panel with blown in cellulose.
I have the main breaker panel already installed. Pretty basic wiring. 4 receptacle circuits, 3 light circuits, 1 exterior light circuit, a 50 amp welder circuit and a 30 amp compressor circuit pretty much does it. All wiring will be in the walls. I hate conduit running around. I AM going to screw the OSB to the girts so that any future wiring could be done without tearing anything up.
The question is: Is there any advantage either way in doing the wiring before or after the 1-1/2" of foam? Pro's and Con's?

 

[Subutai]

This isn’t an expert opinion but I would assume it would be easier to do the wire runs before the foam.

 

[Toolfool]

I wired first.

 

[nadogail]

This isn’t an expert opinion but I would assume it would be easier to do the wire runs before the foam.

Installation of the electrical system after the foam has been sprayed will be much more difficult and expensive than if it had been done prior to the foaming of the building.

 

[Joe Reed]

If you're only doing 1.5" on the walls only and doing your own wiring I can't see why it would be more difficult or expensive to do after the foam. Since it's a pole barn I'm assuming your cavities are at least 6" or so. That leaves plenty of room for you to install the wiring.
The potential advantage I see of doing the wiring last is that any future changes or repairs you might make would be unemcumbered by the foam.

 

[jaw22w]

Yeah, I've been going over this in my head for a couple of weeks now. My slab goes in Monday. so, this is getting to be a pressing decision. I'm leaning towards wiring first, but as said that buries the whole system.

 

[Spud McGee]

For my pole barn, I ran the wires right against the metal. Its sitting on the girts, between the metal and the posts.

When I come back in and insulate, that will cover the wiring up.

 

[36truck]

I would do it after then you can run the wires along your purlins.

 

[Firebrick43]

I am doing the interior of my new 30x40x12 pole barn. The next step is wiring or spray foam. I am doing the wiring, and the foam will be hired out. I am only getting 1-1/2" closed cell foam on the walls only. That will seal up the building. Then use R-19 fiberglass to finish. Walls will be covered with OSB on horizontal girts on the interior face of the poles. The ceiling will be white liner panel with blown in cellulose.
I have the main breaker panel already installed. Pretty basic wiring. 4 receptacle circuits, 3 light circuits, 1 exterior light circuit, a 50 amp welder circuit and a 30 amp compressor circuit pretty much does it. All wiring will be in the walls. I hate conduit running around. I AM going to screw the OSB to the girts so that any future wiring could be done without tearing anything up.
The question is: Is there any advantage either way in doing the wiring before or after the 1-1/2" of foam? Pro's and Con's?

Why not just put xps foam between the girts?

Its a lot cheaper, better insulation, and doesn't void the steel siding warranty or have rust issues later from holding water against the siding. Nor is there any issues "sealing" the wire. Installed with a foam gun its sealed as well to.

 

[shortykorte]

Generally you install all in wall systems and penetrations then spray so you get a good seal and don’t have to hack open the foam especially if doing closed cell.

 

[LXCam]

First plus run some future strategic conduit stubs. Even if it’s nothing more then some 4s deep bracket boxes with a 3/4” stub up to the truss level. Once you foam, it’s a mess going backwards.

 

[brianpgriset]

I had the exact same question as you with a similar building setup. Mine was traditional 2x6 framing with 2x4 purlins so I had 7” of stud bay depth for 2” of foam. I chose to do electrical after and it was the right decision. See the thread here —> https://www.garagejournal.com/forum...builiding-many-questions.468473/#post-8827813

All in all I had plenty of bay depth to run all wires and it took 30 seconds to scrape the tiny bit of foam off the sides of the stud to mount a box.

The benefits are as mentioned, you can make changes to your design after foam with ease. I also had significantly more electrical than you.

 

[jaw22w]

Why not just put xps foam between the girts?

Its a lot cheaper, better insulation, and doesn't void the steel siding warranty or have rust issues later from holding water against the siding. Nor is there any issues "sealing" the wire. Installed with a foam gun its sealed as well to.

My barn was built with 2x6 girts at 3' centers. That doesn't lend itself well to 1-1/2"x4x8 sheets of foam. I have 1600 sq.ft. of wall to insulate. It would take at least 50 sheets of patched together foam boards to cover and you would still not have insulation on the girts. 50 times almost $40 bucks plus sales tax. $2000+ for foam board insulation plus my labor to install. $3300 for 1-1/2" spray foam. The sealing qualities alone are worth the extra money.
This barn has a wainscot. At the upper and lower siding juncture and the top and bottom of the siding, there is a small gap that shows daylight when viewed from the right angle. Foam board would never seal that up to my satisfaction. Air moving through fiberglass insulation just about kills its insulation value.
LOL! If the foam causes rust issues in 25 years, my son can deal with it. I'm 73 years young.

 

[jaw22w]

One of my concerns with foam before wiring is supporting the wires in between the 8' o.c. posts when running receptacle circuits. The girts will have 1-1/2" of foam on them also. So, can't fasten to the girts. I don't like the idea of 12 ga wire just dangling between posts. Also, trying to install 4 exterior outlets would be more difficult and would have to be sealed after installation.
I'm still leaning to wiring then foam. I have a few days yet.

 

[Kpaige]

After

Run some conduits in spots you may need to add stuff in the future.

 

[Augus7us]

The only way I would run wire after is if it was surface mounted in conduit. Spray foam is not an exact science, even if you request 1.5" you may get 3" or 4" in some areas and find yourself spending too much time scraping and sawing away foam.

 

[Augus7us]

For my pole barn, I ran the wires right against the metal. Its sitting on the girts, between the metal and the posts.

When I come back in and insulate, that will cover the wiring up.

Off topic a bit, but I did this (stapled my wire to my girts), except I had a lot more wire... And the end result is not pretty nor am I proud of how that turned out. If any of you are considering running your wire like this but have many circuits, do this instead. Every other or every second stud bay nail a piece of 1/2" osb maybe 1' x 3' and nail it to two of your girts. Use this to staple your wire instead of the girts for a cleaner look and the ability to run many circuits.

I have a GJ amount of outlets in my shop

 

[Spud McGee]

Off topic a bit, but I did this (stapled my wire to my girts), except I had a lot more wire... And the end result is not pretty nor am I proud of how that turned out. If any of you are considering running your wire like this but have many circuits, do this instead. Every other or every second stud bay nail a piece of 1/2" osb maybe 1' x 3' and nail it to two of your girts. Use this to staple your wire instead of the girts for a cleaner look and the ability to run many circuits.

I have a GJ amount of outlets in my shop

Thats why the building has 5-6 girts. And each girt has a top and a bottom edge.