How BIG can holes be in Pole Building vertical posts?

[bobinyelm]

Not sure where is the right place to ask, so I posted it in 2 places.
It's not an "electrical" question, so I thought maybe here was appropriate?

I am about to start wiring my new 32X60ft shop, and there are places that the wiring "needs" to pass through the structural poles that are 6"X8" or 8"X8" depending where they are located.

Is there a place one can find tables or such that say how large holes drilled through the vertical support poles can be for the purpose of running wires? At corners, I would drill intersecting holes at 90 deg to pull wires through.

The inside of part of the shop is studded flush to the inside surfaces of the square poles, so installing conduit is otherwise not required since the wiring will be behind sheet rock as in a conventional building.

ALSO, there is a 1 1/2" space behind the posts (the sheet metal sheathing outside is spaced by 2X6s off the posts. Is it OK to run the NM wire behind the posts (between the posts and the vapor barrier/insulation that is against the inside of the steel siding)?

 

[dmcintosh]

I ran my wire behind the posts as you suggest and my inspector had no problems with it. Certainly easier than drilling through the posts.

 

[rburke65]

Could you run wiring up and over or ....before you poured the floor......run conduit under then up to where you need it? And photos of the problem area?

 

[bobinyelm]

In most places I CAN run behind the posts, but in others, it would add a LOT of wire to the equation, especially corners.

Being the shop is built and in-place, doing anything under the slab is not possible.

There will be places where going through the posts is the most reasonable thing to do, if I can do it. Certainly drilling through load bearing 2X4 walls is accepted, so I have to think that a 6X8 or 8X8 can live with a hole or two. I'd be confident that a 3/4" hole wouldn't weaken the posts (plus I have a LONG 3/4" ships auger), but in places 3/4 won't be enough, though I could drill two spaced, but fairly close together.

I have a 1 7/8 Forsner bit that I could enter opposite sides of a through-pilot hole to meet in the center.

 

[sberry]

Up a ways its not so bad and at corners not such an issue. The bigger the hole the worse of course.

 

[LXCam]

You really think you're going to use that much extra wire going around the pole? I'd suggest you don't pitch pennies to spend dollars.

 

[bobinyelm]

You really think you're going to use that much extra wire going around the pole? I'd suggest you don't pitch pennies to spend dollars.

The inspector told me that I cannot expose the MN cable on the OUTSIDE of the posts or structural members where people might accidentally come into contact with it and chafe the wire's insulation.

If you are suggesting that I go around the back corner of the corner posts under the siding (as I can along the straight sections, it is too tight to bend around in a 90 deg behind the corner posts.the

Thank you for the financial advice, however. I am guilty of trying to save pennies where I can, especially if I have a good reason, and my wife would advise the same as you do. But that was not the motivation in this case.

 

[LXCam]

The inspector told me that I cannot expose the MN cable on the OUTSIDE of the posts or structural members where people might accidentally come into contact with it and chafe the wire's insulation.

If you are suggesting that I go around the back corner of the corner posts under the siding (as I can along the straight sections, it is too tight to bend around in a 90 deg behind the corner posts.the

Thank you for the financial advice, however. I am guilty of trying to save pennies where I can, especially if I have a good reason, and my wife would advise the same as you do. But that was not the motivation in this case.

With the wire running on the outside of the post in the space created by the girder that is covered by the exterior sheeting the wire or conduit is not exposed to physical damage and is considered protected. And not knowing what size you plan on running cannot say it will or won't work around the outside corner of the post.

And maybe next time you might think about how you worded your original post where you stated that running around the post would use too much wire which is just ridiculous which is why I poked fun.

Good luck ta ya, I'm out.

 

[bobinyelm]

Could you run wiring up and over or ....before you poured the floor......run conduit under then up to where you need it? And photos of the problem area?

The place I am trying to go through a post here and there is above the 8ft level, especially at the corners where I can't go behind the posts. Anything below 8ft need to be in finished walls (sheetrock) or be inside conduit, or using BX armored cable, both of which I am trying to minimize.

I have a storage loft over one bay, and I have to check w/ the inspector if the loft is considered "living or working space" and also requires conduit or BX for any wires below 8ft height in the loft (15 ft above the concrete floor)..

 

[bobinyelm]

And maybe next time you might think about how you worded your original post where you stated that running around the post would use too much wire which is just ridiculous which is why I poked fun.

Good luck ta ya, I'm out.

I know you're "out," but I re-read my original post and I said nothing about it using to much wire to go around the post.

Later on, I mentioned that, but meant that re-routing the wire in completely different paths (to completely avoid the corners) would add a lot (like 50 feet), and that would add resistance to the circuit as well as waste wire.

If I were concerned about a foot of wire going around a post, I agree it WOULD be ridiculous. Sorry I upset you.

Bob

 

[WittHay]

The open farm type sheds i have seen never have open holes in the posts. There is always a bolt in them. Usually the wire is run overhead and dropped down as needed

It probably depends on spacing of the posts and how strong the walls and siding are built if you want to drill holes in the posts.

 

[bobinyelm]

I know in old New England barns, the posts and beams were FULL of holes (well over an inch in diameter) but always had wood pegs in them to secure (and large sections removed to mate) intersecting beams.

I will have over 600 feet of wire of various sizes (some of which is $2/ft or more) and 60 switch and outlet boxes so I am trying to avoid gross runs of cable where I can run it more efficiently.

I am certainly not wanting to weaken the structure, but thought maybe there were 'rules of thumb" with regard to holes in the poles, but from the lack of responses, I would guess not.

I do know the poles have some large knots, and some corners have missing sections of knots of 1 1/2" or so and the building inspector was OK with them.

 

[WittHay]

I would get a on site professional opinion rather than internet advice. Building codes vary and the trouble on the west coast is sometimes we get a heavy snowfall and then it rains the next day. That's a lot of weight up on a roof.

 

[Elginz]

Notching or boring into
columns is not recommended
and rarely acceptable;

From NOTCHING & BORING GUIDE
Don't know if it fits your application.

 

[bobinyelm]

I would get a on site professional opinion rather than internet advice. Building codes vary and the trouble on the west coast is sometimes we get a heavy snowfall and then it rains the next day. That's a lot of weight up on a roof.

Not bad advice.

I will make an appointment with the County Building Department and ask them their opinion, though with past questions I've asked, they have advised hiring of a licensed professional engineer to approve a proposal with his stamp, and submit it with a formal permit for approval (with appropriate fees). They are understandably hesitant to render opinions that could incur legal and financial liability (say, should the building later fall down), and prefer to have a P.E. have his license/insurance accept that liability.

My last such attempt cost me around thirteen hundred dollars ($200/hour) to a P.E., but it was for a structural question regarding how my home builder deviated from the official plans provided to me and the County. Maybe the County will be more forthcoming on this one.

 

[bobinyelm]

Notching or boring into
columns is not recommended
and rarely acceptable;

From NOTCHING & BORING GUIDE
Don't know if it fits your application.

Ah HA!

I used your term (NOTCHING & BORING) and found this guide:

http://co.routt.co.us/building/handouts/notching.pdf

Sometimes finding Internet information depens upon the search term and that one you used was perfect.

Thanks

Excerpt:
Notching and Boring - IBC Section 2308 & IRC R502.8 - R802.7.2
Joists, Studs, Rafters, and Beams
"The diameter of holes bored or cut into members shall not exceed one-third the depth of the member in size. Holes shall not be closer
than 2 inches (51 mm) to the top or bottom of the member, or to any other hole located in the member."

screen cap

 

[checkthisout]

In most places I CAN run behind the posts, but in others, it would add a LOT of wire to the equation, especially corners.

Being the shop is built and in-place, doing anything under the slab is not possible.

There will be places where going through the posts is the most reasonable thing to do, if I can do it. Certainly drilling through load bearing 2X4 walls is accepted, so I have to think that a 6X8 or 8X8 can live with a hole or two. I'd be confident that a 3/4" hole wouldn't weaken the posts (plus I have a LONG 3/4" ships auger), but in places 3/4 won't be enough, though I could drill two spaced, but fairly close together.

I have a 1 7/8 Forsner bit that I could enter opposite sides of a through-pilot hole to meet in the center.

You can get two 12 gauge wires through a 5/8 hole. You can only put 2 NM cables per hole so drilling bigger holes is pointless.

My personal recommendation would be that you go ahead and finish out the interior and then run conduit. Less pre-planning and guessing where shelves will be, less cutting of finish materials to fit around boxes etc. Just a lot less work and more versatility at the end of the day.

 

[rburke65]

Shoot a few photos of the area in question and that will help us a lot.

 

[Elginz]

But not for columns, it is for joists, Studs, Rafters, and Beams

Ah HA!

I used your term (NOTCHING & BORING) and found this guide:

http://co.routt.co.us/building/handouts/notching.pdf

Sometimes finding Internet information depens upon the search term and that one you used was perfect.

Thanks

Excerpt:
Notching and Boring - IBC Section 2308 & IRC R502.8 - R802.7.2
Joists, Studs, Rafters, and Beams
"The diameter of holes bored or cut into members shall not exceed one-third the depth of the member in size. Holes shall not be closer
than 2 inches (51 mm) to the top or bottom of the member, or to any other hole located in the member."

screen cap

 

[rayra]

haven't seen anyone asking a more key question, why not run your cables in surface mounted conduit. Or if you have (or will have) an interior skin on your structure, why not shim that wall out from your poles and pass your wiring thru the shims, instead of boring holes in your structural poles?

What exactly is the problem you are trying to solve? Shielding the wires? Visually hiding them? Saving a few bucks by going thru instead of behind?


btw, you answer on the square corner posts is pass the wire behind them at a 45deg up/down angle. You gain a bit more room for bending a stiff cable that way. Takes a bit more cable that way. Typically the hack is rather to notch the interior corner so the cable passes thru it and fits behind the wall sheathing.

And the answer to 'they drill thru on [stud] walls' is they aren't typically structural members or bearing walls, and even when they are there's a vertical member every ~16". instead of a tall pole every 4'-12' with a larger load and a much larger moment arm. If you feel compelled to bore thru I suggest you do it as high up as practicable. Bad idea to bore thru near ground level.
Next time you see a metal guardrail on a road with wood posts, you might notice they put a large bore hole thru the posts near the ground. That's so they shear off easier during a vehicle impact.

 

[matt_i]

But not for columns, it is for joists, Studs, Rafters, and Beams

I completely agree. That's a double supported beam with the idea there are similar supporting members each side.

The column is cantilevered and has no backups so to speak. Drilling a hole 1" up from the dirt is very different from drilling it 1" from the top in terms of the structure.

I would treat the post just like an engineered truss: no drilling or notching unless P.E. approved. Instead run wire up and over. Daisy chain on the horizontal.

Another way to look at it. I could potentially run a wire in a 30x40 shop, 70 feet or more from one corner to the opposite diagonal and I expect no voltage drop issues on #12 awg.

 

[MagKarl]

If you carefully remove your vertical outside corner trim, you may find it's not that difficult to pass wire around the outside of the corner posts.

 

[johninct]

You should run all of your wires in conduit or come from the top down.

 

[bobinyelm]

Just came from meeting with my State Electrical Inspector and asked my questions.
Some insights-

1) Every single circuit in the entire shop needs to be GFI, even the overhead lighting circuits.
2) Every outlet EXCEPT the ceiling lighting circuits must use TR Receptacles, and that includes the door opener outlets.
3) No interior lighting should be controlled by a circuit that powers any receptacle.
4) No exterior lighting circuit (regardless of height above ground) may be hooked to a circuit supplying interior service, even though that circuit is GFI'd.
4a) Exterior circuits must be a dedicated outdoor circuit, period. To avoid having a separate circuit just to power ONE light bulb above the entry door (required) that may require a GFI breaker and 75ft of cable (potentially $50 in parts just to power a single light bulb), you MAY install a proper outdoor receptacle (GFI), and power the light bulb from that circuit, though it is discouraged), which at least blunts the cost for that circuit.
5) All wiring below 8ft above any accessible by a human must be "protected" either in conduit, by being armored cable (BX), or protected by mounting method.
You can install NMC (Romex) without conduit IF it is stapled UNDER* a purlin (skirting board) in a pole building, or of course, if it is behind a sheet rocked wall.
(stapling cable to the UNDERSIDE of a purlin is considered "protected," while on the top side is NOT "protected," though stapling on the top side of a purlin is fine if it's above 8ft.
"Accessible by a human" could be an area used for storage only, even if accessible by stairs or a ladder.
6) NO circuits in a detached shop needs to have an AFCI (arc fault breaker).

I asked about running conduit to avoid drilling a hole in a pole (post). The answer was, "Why don't you want to drill a hole in your pole (post)?" He said that as long as holes are drilled according to recommended criteria, the frame is not measurably weakened. He said drilling a single 3/4" hole through an 8"X8" beam using "common sense" is not a problem compared to using conduit for one's entire shop (unless one really WANTS to install it). A personal decision, though of course it would depend upon your building department, and whether paying a P.E a few hundred dollars (one hou's time) is worth it.

The one question I forgot to ask (I will try calling during the inspector's 30 minute allowable window every other day to ask) is whether one can run wire NOT in conduit above 8ft, then have it enter conduit at that level, terminating in a box below 8ft.

I am not saying what I was told was correct, only that that is what I was told by the inspector assigned to me (who has 30 years experience) will be looking for, so I am building to HIS code, rather than a code I looked up myself, so Caveat Emptor. My inspector could be wrong, and your Code may vary by area.

 

[sberry]

Sure, pipe it down to a box, its protected and pipe is as good as it gets. I figured the inspector would buy drilling modest holes in a post, its done all the time. I agree with his preference for keeping lights off recept circuits.

 

[Jeepster04]

Good gosh, thats some insane rules there.

So is it ok to run it in the ridge of the exterior metal between the metal and the purlin? Would that be considered 'protected.'

Technically I can access anything...

My plan was to buy metal conduit to run the power down to the box. My poles are going to be exposed so Ill nail the box right to the side of the pole. Either that or run the power down the ridges in the exterior metal behind the purlins and into the back of the box. Ill be running everything in the attic space, no drilling of anything for me.

 

[checkthisout]

Yes you can do drops in conduit.

 

[bobinyelm]

Yes you can do drops in conduit.

I was wondering if I have to do anything but champher the upper "naked" end of the plastic conduit (where the "unprotected" NMC enters the conduit) to prevent chaffing of the NMC outer jacket, or is there a fitting I'd have to terminate the conduit with that would provide chaffe protection?

I was surprised that the door opener receptacle at 12ft height requires a TR receptacle, yet the receptacle 3 feet away for the lighting fixture to plug into does not require a TR unit.

I mentioned that I dislike TR receptacles since they allows only the end portion of the plug blade to make electrical contact in the receptacle. He agreed, saying that some of their testing equipment will not work with TRs, but we both acknowledged that "rules is rules."