Hi all,
I am replacing some under size 8/3 romex with 6/3 wG due to the fact that I am replacing my range as well with a new self cleaning unit. I can’t get to the old wire well enough to consider trying to use the old holes in the joist. So I am looking at drilling about fifteen joists for the new wire.
I looked at an article in FHB on common framing errors and found it helpful i.e. drill 2 inches up from the bottom of the joist, don’t drill in the middle third of the joist etc.
My question is will I compromise any structural integrity by placing all the holes in a straight line to the new range location or should I offset each hole a little, in other words don’t run the 6/3 wG perpendicular thru each joist but run thru at an angle? I really hope that I can just run the new wire perpendicular thru the joists as it would reduce the amount of wire I need to buy and make the pull easier. I have plenty of access, the garage ceiling is unfinished but it is never easy to pull wire over head thru a lot of small holes.
Any thoughts will be appreciated.
Chris
Replies
Run the holes straight through-perpendicular as you wish. Just like you said. No holes in middle third and holes 2-inches from top or bottom. Holes in the middle of the joist top to bottom are best (along the neutral axis) but tend to be harder access. Just drill the holes bigger for ease of pulling and less potential for damage to wires (about 1-1/4 inch dia. +/-). No decrease in strength whether holes are angled or perpendicular as you discuss.
Edited 10/23/2003 1:25:13 PM ET by akela
Atually, it's BETTER to have the holes in the middle third of the joist, and roughly centered between the top and bottom edges.
I'd keep them in line from one joist to the next - Staggering them won't do any good.
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The one thing that hasn't been mentioned yet is that the maximum diameter for holes in joists is 1/3 of the width. This would matter with 2x8's or larger, on 2x6's, the 2" from the edge rule would restrict the maximum hole to less than a third of the width.
Let's see, holes are better in the middle of the joist, but notches are forbidden there. Notches are better near the ends.
I think that just about covers all the issues with running stuff thru joists.....
-- J.S.
I think there is some confusion (at least I'm confused) about whether "middle third" refers to 3rds as the board is divided horizontally or vertically. Can some one offer some clarification here please?
i'm gonna take a shot at this- i think they mean:
DO drill in the middle third of the height of the joist member (ie. for a 2x10, between say about 3.25" up from the bottom edge and down from the top);
DON'T drill in the middle third of the length of the joist (ie. for a 21ft joist, don't put holes between the 7' and 14' points)
please stand by for a correction from someone who knows what they're talking about.
m
Hi Mitch and all,
Thanks so much for your info and quick replies, I really appreciate it. Mitch that is what I meant. I should have been a little more clear when I said the middle third of the joist I meant the middle third of the length.
Thanks again everyone.
Chris
I think you've got it backwards.
Drilling in the middle third is better. In the middle of the joist span, you have more tension/compression and less shear. The part of the joist that's above the hole is in compression, and the part below is in tension.
Notching is better near the ends because you have less tension/compression and the shear generally isn't a controlling issue.I smile because I have no idea what's going on.
OK, I'm not being intentionally obtuse here. I just want to make sure we got this straight. If I draw two lines from end to end on a 2x10-12' so that that the board is now divided into 3 sections 3 1/6" x 12', I should not drill in that middle section. Right?
Or, rather, if I divide that 2x10-12' lengthwise into 3 sections 4' long, do I not drill into the middle section?
I know I've seen all this a few times with pictures and everything. I can look it up, I suppose. The fun part, and the challenge, is being able to put this into precise language that is unambiguous and clear. Something I obviously don't have the talent for.
so, you want to shoot more or less for the middle both within the height (top to bottom) of the joist member AND its span (end to end)?
the other part i want to clear up t'is whether t'is better, within the height of the joist member, to leave relatively more above or below the hole. wood has excellent compressive strength but generally poor tensile strength, so you'd want to err on the side of leaving more wood intact below the level of the hole- bottom chord in tension- to lend a hand where it's weaker, n'est pas (bad french for, ain't that right)?
btw- i'm not drilling any holes anywhere at the moment, but in my high school days i was into model bridge building (colorado state champ my senior year, actually) and this stuff still fascinates me.
thanks, m
OK, bridger, you've got a box beam bridge. . . where is the best place to drill holes in the vertical sides of the box?
SamT
Edited 10/23/2003 5:57:17 PM ET by SamT
If I draw two lines from end to end on a 2x10-12' so that that the board is now divided into 3 sections 3 1/6" x 12', I should not drill in that middle section. Right?
Wrong - any holes should be in the middle 1/3 of the height - but not in the middle 1/3 of the length
Or, rather, if I divide that 2x10-12' lengthwise into 3 sections 4' long, do I not drill into the middle section?
Right
CORRECTION: The illustration is wrong - I was thinking of notches, not holes
_______________________
Albert Einstein said it best:
“Problems,” he said, “cannot be solved at the same level of consciousness that created them.”
Your mileage may vary ....
Edited 10/23/2003 9:44:43 PM ET by Bob Walker
Sounds like we have a full-fledged disagreement here. Could this rival the venting wars?
Take your 12' joist, and draw vertical lines at 4' and 8' from one end. You SHOULD drill inbetween the vertical lines at 4' and 8'.
The holes should be roughly in the center of the joist - Like 4 5/8" up from the bottom of a 2X10.
You should NOT drill within 4' of the ends.
Bob Walker's drawing is wrong, IMHO.
Again, I would point out that it's best to check with your LOCAL code people. This is obviously something that isn't agreed on, and your local people may have their own ideas. They're the ones that are going to stick it to ya if they don't like what they see.Two Eskimos sitting in a kayak lit a fire in the bottom of their kayak to keep warm. It sank, proving once and for all that you can't have your kayak and heat it too.
For LVL beams, the holes MUST be in the center third of the span, and on the centerline vertically. Now, I know you are talking joists, and this is lvl beams, but...
http://www.gp.com/englumber/pdf/123040/50-52.pdf
But, on the other, hand,
Notches on the ends of joists shall not exceed 1/4 the joists depth. Holes bored in joists shall not be within 2" of the top or bottom of the joist and the diameter shall not exceed 1/3 the depth of the joist. Notches in the top or bottom of joists shall not exceed 1/6 the depth and shall not be located in the middle third of the span. [Section 2517(d)3]
from http://www.hawaii-county.com/permits/info_const.html
Edited 10/23/2003 9:36:39 PM ET by Cairo
The Hawaii county code you cited is a local one. That's the reason I suggested that everyone check locally - It goes against the norm.
The .PDF document Piffin posted was made by the Western Wood Products Association, so I'd say it carries some weight. I don't know if the other lumber associations have similar guidelines or not - I haven't been able to find them if they do.Q: Which sexual position produces the ugliest children? A: Ask your Mom.
BH - you';re right, I was wrong - I was thinking of notches .
CABO says in the middle third of the height, another source I found for specing pipes gets very complex:
http://www.equator.co.uk/newwebsite/design_technical.html
But see, CABO:
CABO, Section 502 Floor Framing
502.6 Drilling and Notching. Notches in the top or bottom of joists shall not exceed one-sixth the depth of the joist and shall not be located in the middle third of the span. Where joists are notched on the ends for a ledger, the notch shall not exceed one-fourth the joist depth. Cantilevered joists shall not be otched unless the reduced section properties and lumber defects are considered in the design.
502.7 Holes. Holes drilled or bored in joists shall not be within 2 inches (51 mm) of the top or bottom of joists, and their diameter shall not exceed one-third the depth of the joist.
http://greenwichct.virtualtownhall.net/Public_Documents/GreenwichCT_DPW/GreenwichCT_BldingDocs/NotchJoist.pdf
_______________________
Albert Einstein said it best:
“Problems,” he said, “cannot be solved at the same level of consciousness that created them.”
Your mileage may vary ....
1) that was over 25 yrs ago
2) my specialty was arches of one sort or another, not box beams
3) that means i have absolutely no friggin idea- you have stumped the panel.
m
After reading all the posts in this thread, I still can't seem to get consensus on where holes can be drilled along the span. Sounds like as long as you stay away 2" from top and bottom, you can drill anywhere along the span. Can you confirm?
Refer to 2000 IRC for One and Two Family Dwelling:
R502.8.1 Sawn Lumber ..... 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.
R502.8.2 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.
In other words, for sawn lumber - drill along the length where you wish - any third but not closer than 2" from the edge or any other hole or notch.
for Engineered wood products - only per the manufacturers or engineers specifications.
"BH - you're right, I was wrong..."
You know I have to bookmark that one, don't ya ???................(-:It's not the years in your life that count. It is the life in your years. [Abraham Lincoln]
IIRC, the rules are different for i-joists and solid wood. This may explain some of the disagreements here.
Just as a clarification:
Shear is always worse near the supports of a beam or joist (i.e., near the ends) or right next to a point load. Since floor joists are usually not likely to experience point loads (unless a load bearing wall lands on them), shear can usually be expected to be worst at the ends of the joist.
Bending moments (which cause the tension and compression forces everyone's talking about) are worse away from the supports. Not to sound to engineerish about this issue, but whether it's better to drill holes near the ends of the joist or near midspan will depend on the factors of safety for shear and bending moment. If bending moment is closer to causing failure of the member, then don't drill near mid span where the moment is the greatest. Similarly, if shear is the biggest concern, don't drill near the ends of the member where shear is the greatest.
Unfortunately, all this stuff doesn't tell you where to drill. For that, you'd need to determine if shear or moment is the greatest concern. To do that, you basically have to calculate the shear and moment continuously along the length of the joist and compare these values to the allowable values for the joist.
I know that no one does this in real life but just wanted to provide a structural perspective.
Everything you say is basically true. But most guys drilling holes in stuff don't know about bending moments or shear. Thus the general necessity of general guidelines.Talent is that which is in a man's power; genius is that in whose power a man is. [James Russell Lowell]
You can put any size hole anywhere you want in a concrete dome. Oh.....that wasn't the question, was it. :) Carry on....
When they talk about drilling in the middle 1/3 of a joist, they're talking about horizontaly.
When drilling holes, theoretically you should leave as much wood above it as below it. The top flange is in compression, and the bottom in tension. Although wood has more strength in compression than tension, so more "meat" left at the bottom should be better.
I've been checking around, trying to find a reference to this stuff on the web. Came up dry so far, and can't even find anything in my books in the office.Common sense isn't very common.
"Let's see, holes are better in the middle of the joist, but notches are forbidden there. Notches are better near the ends."
That's basically how I understand it.
But it might be worth mentioning that a building inspector might have his own ideas, and it would be worth checking with him.Successful people form the habit of doing the things failures don’t like to do
Hi,
Double check your information for joist drilling. I believe you should have the correct information as:
1 - Holes must be a "minimum" of 2 inches from the joist edge.
2 - The hole can not exceed one-third of the joist width.
3 - Ideally, you would want to favor the hole "in the middle third" of the joist width.
4 - I would run a line of holes straight and perpendicular, which is to your advantage as you stated. It also looks nicer and makes for better conditions when upgrading other utilities or whatever.
5 - Truss-Joists are another matter to consider. Watch that you cut and drill within the guidelines that you can find at their web site or the paper that you might find at a Trus-Joist dealer.
Don't forget to check your local code and contact your local electrical inspector, before you purchase components and do the work, so that you don't have to do it twice.
Regards,
Virginbuild
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