HR's - a few large holes or a bunch of smaller ones?

[bjp_ne_elec]

Curious what approach you take - either drill a few larger holes (1-1/2" or so) or drill a series of smaller holes when routing home runs of NM (or MC for that matter) back through floor joists and vertically through the floors (but you'd be drilling in the horizontal top and bottom plates.

If you do use smaller holes, what size and how close?

Edit - I've just read a few posts that I found by doing a search on "drilling joists" - and now I'm a little confused. First when driling say 7/8" holes in joists, how close can they be. One thing I read was regarding drilling 1-1/2" holes and it indicated there had to be 1-1/2" from edge to edge of the hole. Does this mean 7/8" holes also have to have 7/8" edge to edge? Also is the criteria different if you're talking drilling the top and bottom plate? I don't see how you maintain that spacing when you're trying to bring your HR's down through the first floor space.

Thanks,

Brett

[Dennis Alwon]

If you drill large holes than you must drerate once you have more than 2 cables in the hole if the holes will be fire caulked-- art. 334.80 last paragraph.

I usually use 7/8" holes close together and I also use stud bays on both sides of the panel.

[bjp_ne_elec]

Dennis - what's a "stud bay"? Also, you say you drill them "close" - is there no concern for weaking structural members? I just want to understand what criteria I burn in to memory. From reading the third post in this ( http://forums.mikeholt.com/showthread.php?t=59646&highlight=drilling+joist ) thread, there's diffentiation between what can be done with a joist versus a top/bottom plate.

Thanks

Dave

[Dennis Alwon]

The stud bay is the area between 2 studs. The panel fits in one stud bay and we have access (sometimes) to stud bays to the right and left of the panel.

If you keep your holes in the middle it wont weaken the wall.

When you have many wires in the panel uses just the top plate is not enough that's is why I go to the left or right of the panel bay. Once I penetrate the top plate I can go horizontal with more wires since it won't be caulked.

In our area they will not allow more than 2 wires in a hole. I have not had that issue yet but I plan on challenging it.

Sometimes I use the other bays to go down to the bottom of the panel esp. If I am in the basement where you can't go through the floor.

[ceknight]

Curious what approach you take - either drill a few larger holes (1-1/2" or so) or drill a series of smaller holes when routing home runs of NM........

If I have enough HRs to fill several large holes in each joist, I start thinking about installing a subpanel instead. :)

[360Youth]

I use a 7/8" auger bit for the majority of my drilling, vertical or horizontal. At times I will use a 1/2" bit so I can use a more manageable drill, it depends on the circuit and/or house. If I have a solid joist house inbetween floors, I will use an 1 1/4" so to cut down on the # of holes. The rule I know as far as solid joist and certain beams (some you cannot drill at all, now that is fun:rolleyes: ), is to stay away from the inner 1/3 of the beam. It is off limits to boring. Or so I have been told by GCs. For HRs I use large holes with a coule of small ones if necessary.

[bjp_ne_elec]

360Youth - what do you consider the "inner 1/3"? You're talking about joists - do you mean the upper third (closest to the side the upstairs flooring is nailed to) or the lower 1/3 (where the sheet rock would be screwed to?

Thanks

[stickboy1375]

360Youth - what do you consider the "inner 1/3"? You're talking about joists - do you mean the upper third (closest to the side the upstairs flooring is nailed to) or the lower 1/3 (where the sheet rock would be screwed to?

Thanks

The middle third.... In between the two outside thirds...:smile:

[bjp_ne_elec]

Stickboy - that's why I questioned it - he is indicating you have to "stay away from the inner 1/3" - I'm thinking you only want to be in the "middle third". See my point?

[j_erickson]

The MA building code states that holes shall not be in the middle third of a span, shall not be within 2" of the top or bottom of a joist, and shall not be within 2" of another hole, and diameter of the hole shall not exceed 1/3 the depth of the joist. This is for dimensional lumber. For engineered lumber, you must follow the manufacturers instructions.

With regard to drilling top and bottom plates for HR's: I try to have my panels located in the basement directly below the stud bay where I drop to the basement. So nearly every home run runs overhead therough the first or second floor. In this case, I drill 2 or 3, 1 3/4" holes in the top and bottom plates for all my cables to drop to the cellar. There is no regulation for how close these holes may be to each other, nor how big they can be. Essentially you could cut out the whole top and bottom plate of this stud cavity as long as it were firestopped afterward. Every other hole that I drill for running wires is 7/8". Except for some alarm wires which get 3/8" holes.

edit: So I'd say 360 was trying to say what I just quoted above. Note that with engineered joists, the middle third of the span is where you can cut your largest holes. Just opposite of dimensional lumber.

[LawnGuyLandSparky]

If I have enough HRs to fill several large holes in each joist, I start thinking about installing a subpanel instead. :)

This is going to become quite an issue when 80 circuit panels become the norm...

[SurfSide EC]

edit: So I'd say 360 was trying to say what I just quoted above. Note that with engineered joists, the middle third of the span is where you can cut your largest holes. Just opposite of dimensional lumber.


That about sums it up:grin:

This is going to become quite an issue when 80 circuit panels become the norm...

Ewww. Can you imagine one of those with a dozen AFCI and GFCI breakers. Talk about a nest. What would an 80 circuit panel be rated at??

[Dennis Alwon]

This is why you try and plan your house with sub panels. Less drilling and shorter runs. I rarely have just a main panel. If it is a two story house I always put one up there to serve that space. It also gives access to power from the attic above--if there is an attic.

The issue of drilling the joist in the middle versus the outer 1/3 of the joist (length dimension) does not usually apply to a small hole such as a 7/8" .

[j_erickson]

This is why you try and plan your house with sub panels. Less drilling and shorter runs. I rarely have just a main panel. If it is a two story house I always put one up there to serve that space. It also gives access to power from the attic above--if there is an attic.

The only reason I don't do this is because if someone wants to be able to set up circuits for use with a small gen-tran, they basically can't. If I do subpanels in a house, it will usually be a larger house than average. And then I'll usually run a pipe between main panel and subpanels.

The issue of drilling the joist in the middle versus the outer 1/3 of the joist (length dimension) does not usually apply to a small hole such as a 7/8" .

I agree that a small hole usually is inconsequential. You'll sometimes find knot holes that large. But the building code doesn't address the size of the holes.

[Dennis Alwon]

But the building code doesn't address the size of the holes.

I believe the building code does address the size of the hole. That's way the plummers have to gussett their 3" holes. If you take a certain % of the joist then you have to repair it or gussett it.

I have never had a problem drilling 7/8' holes anywhere in the joist as long as I am in the width center.

[clayton]

what doesit mean to gusset the joist?

[Dennis Alwon]

what doesit mean to gusset the joist?
It could be a metal plate used to strengthen a joist but it is usually a piece of plywood added to both sides of the joist to reinforce it. This allows you to drill a larger hole. The plywood would be as wide as the joist but about 2' long.

[LarryFine]

This is going to become quite an issue when 80 circuit panels become the norm...They may become the norm, but they won't be required.

[clayton]

thanks dennis

[IllinoisContractor]

He is correct about having to leave 2" of wood between the edge of a hole and the top / bottom of the joist.

[j_erickson]

I believe the building code does address the size of the hole. That's way the plummers have to gussett their 3" holes. If you take a certain % of the joist then you have to repair it or gussett it.

I have never had a problem drilling 7/8' holes anywhere in the joist as long as I am in the width center.

What I meant was that it doesn't address "ignoring" holes under a certain size. But I agree, I've drilled 7/8" holes everywhere without ever having an issue. And as you said, if you remove more of a framing member than permitted, you can use some engineered braces to reinforce the stud or joist. I think we are agreeing with each other.;)

[stickboy1375]

CHAPTER 3 – WIRING METHODS AND MATERIALS
(Add) 300.4.1 Drilling and notching.

(A) Structural floor, ceiling and roof members.

1) Solid sawn lumber. Notches in solid lumber joists, rafters and beams shall not exceed one-sixth of the depth of the member, shall not be longer than one-third of the depth of the member and shall not be located in the middle one-third of the span. Notches at the ends of the member shall not exceed one-fourth the depth of the member. The tension side of members 4 inches or greater in nominal thickness shall not be notched except at the ends of the members. The diameter of holes bored or cut into members shall not exceed one-third the depth of the member. Holes shall not be closer than 2 inches to the top or bottom of the member, or to any other hole located in the member. Where the member is also notched, the hole shall not be closer than 2 inches to the notch.

Exception: Notches on cantilevered portions of rafters are permitted provided the dimension of the remaining portion of the rafter is not less than 4-inch nominal and the length of the cantilever does not exceed 24 inches.

(2) Engineered wood products. Cuts, notches and holes bored in trusses, laminated veneer lumber, glue-laminated members or I-joists are not permitted unless the effects of such penetrations are specifically considered in the design of the member and permitted by the manufacturer.

(B) Studs. Any stud in an exterior wall or interior bearing partition may be cut or notched to a depth not exceeding 25 per cent of its width. Studs in nonbearing interior partitions may be notched to a depth not to exceed 40 per cent of a single stud width. Any stud may be bored or drilled, provided that the diameter of the resulting hole is no greater than 40 per cent of the stud

[Dennis Alwon]

My read on that is that you can put a 3" hole in the center of the width of a 2x10 (9.25") floor joist anywhere along its length. WOW.. I don't believe I want to do that.

Sounds like the holes should be 2 inches apart minimum. Oops, I am sure I have been closer than 2" on small holes.

So If I drill a 1" hole, technically I shouldn't be able to drill another hole within 2" of that one. If I drill a 3" hole, then that hole is bigger than 2- 1" holes next to each other. Go figure

[stickboy1375]

My read on that is that you can put a 3" hole in the center of the width of a 2x10 (9.25") floor joist anywhere along its length. WOW.. I don't believe I want to do that.

Sounds like the holes should be 2 inches apart minimum. Oops, I am sure I have been closer than 2" on small holes.

So If I drill a 1" hole, technically I shouldn't be able to drill another hole within 2" of that one. If I drill a 3" hole, then that hole is bigger than 2- 1" holes next to each other. Go figure


I assure you a plumber would not have a problem with it... :grin:

[bjp_ne_elec]

Dennis - I'm not sure it's "anywhere along it's length" - as I think the intent is you can't drill in the middle third of it's span (or length). It reads - "shall not be located in the middle one-third of the span".

Does anyone disagree?

[Dennis Alwon]

Dennis - I'm not sure it's "anywhere along it's length" - as I think the intent is you can't drill in the middle third of it's span (or length). It reads - "shall not be located in the middle one-third of the span".

Does anyone disagree?


That's is for notches not holes.

Notches in solid lumber joists, rafters and beams shall not exceed one-sixth of the depth of the member, shall not be longer than one-third of the depth of the member and shall not be located in the middle one-third of the span.

The section about holes is in the last 3 sentences of the paragraph.

[bjp_ne_elec]

Dennis - thanks - now I see it. I think I understand the criteria now. The job I'm working now, the plumber violated some of the criteria and one of the floor joists ended up splitting - and the GC had to perform some repair.

I don't want to be paying the GC to fix my not understanding this criteria.

Another perfect example of why this forum, and it's members are so AWESOME! Would have made a lot more "whoops", if I didn't have access to this TOOL. It's all about the tools you have (a side note - my wife's convinced I went in to the EC business just so I could buy more tools)

[SeanKelly]

You're always okay drilling the top corners of just about anything as long as you dont go too high as they're not load bearing.

[360Youth]

The job I'm working now, the plumber violated some of the criteria and one of the floor joists ended up splitting .

The forum wouldn't let me respond with a simple "ouch," so I will render my best E.T. and say, "Ooouuch!"