Drilling multiple holes through framing members

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rolanday

Member
Hello,

This is my first post :) . I have read the code regarding drilling holes through framing members but I still have questions I?d like answered before I start drilling. I have a load bearing wall w/ 2x4 framing members. I am running some new NM cable the length of the wall (3 runs in all) in addition to the run that originally existed when the house was built. The wall is in the garage and there is no drywall so access is not a problem.

1) Is there a preferred location to drill the holes? I realize the holes should be centered (1-1/4" to each side of the hole, or use nail plates, etc.) but I am interested in understanding any code relating to positioning of the holes along the length of the stud. I cannot seem to get a straight answer from anything I have read or from people that I have talked to. The holes that were drilled when the house was originally built are away from the center (the outer third of the length) and this seems to make sense from a structural integrity standpoint and also follows the rules for drilling joists (outer 1/3rd of the length). But I have been told and have even seen articles stating that I should drill in the center section of the stud. ???

2) As I mentioned above, I am also planning multiple runs. Are there limits on how many holes I can drill in the stud? Common sense would dictate yes but what is the limit. I plan to have four (4) holes in each stud: two running in the bottom 1/3 of the stud and two more along the top. Is this unwise from the standpoint of structural integrity? Again, this is a load bearing wall and I?m drilling a 5/8? hole in 2x4 studs.

Any advice will be greatly appreciated,

-Roland.
 

rattus

Senior Member
Re: Drilling multiple holes through framing members

Roland,

I would say the hole should be centered horizontally to minimize the possibility of bowing the stud.

The first hole is the weakest point so stacking more holes verically would not weaken the stud further.

Some of the pros might have other ideas though.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
Re: Drilling multiple holes through framing members

The holes that were drilled when the house was originally built are away from the center (the outer third of the length) and this seems to make sense from a structural integrity standpoint and also follows the rules for drilling joists (outer 1/3rd of the length).

Studs are completely different than joists insofar as loading is concerned, so the 1/3 of the length rule doesn't apply. It shouldn't matter at what height you drill your holes, only that you remove a minimal amount of material and keep them centered on the stud above one another. Keep in mind also that studs can be supplemented with additional studs if necessary to increase bearing capacity.

-Hal
 

apauling

Senior Member
Re: Drilling multiple holes through framing members

This is one of those questions that can lead to problems no matter what you propose. I am not disagreeing with anything that has been said.

There are guidelines available in both UBC and IRC building codes under notching and boring. Your holes are minimum and do not rise to any maximum. BUT there are jurisdictions and inspectors that try to impose maximum holes per stud. I have not seen that in the codes and do not understand the source of their requirement.

One point I would like to make is that part of the strength of a stud wall and its sheathing and bracing is accomplished by the shared load of companion studs, and their attachment to sheathing and bracing. Drilling neat and exact holes along any height (at the same height) will weaken the wall more than erratic drilling. It creates, in effect, a controlled joint where the wall will fail, similar to a controlled weak point as a control joint in concrete. The quality of available wood has diminshed so much over the years, and the engineering of houses has explored near maximum utilization of load bearing capacity, that I do not trust old practices, where the safety factor of prescribed framing was nearly double (or better). Common sense about bearing and shear, if you have it, should be uppermost in concern.

As has been already pointed out, fixes are available for damaged or over drilled studs. Where the holes are consistently near one surface, or the holes are quite large, a few sistered studs will help alot, even if attached at right angles.

Another point in old work. The building codes and framing may not have been applied in any manner. Load bearing and shear may be at capacity for any one stud. Augers should not be used in old dry wood as it tends to splinter the wood, destroying much more of the strength than the hole itself. Even with the assumption that most older wood was slower growth, thicker nominal dimension, stronger overall, it was still often maxed out at some points. AND, it must be assumed that other remodeling work has been done and the integrity of the original construction has been breached. A succession of carpenters thinking that it wouldn't hurt to cut just one of something.

If it's your house, a little zealousness might not be out of the picture, even with the minimal drilling. Remember, dry wood splits easier than wet wood, pre-drill if lots of nails along a plane or line, sistered studs if worried. I think a sistered stud is far superior to any of the metal straps in strength in all directions.

sorry for the length

paul :)
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
Re: Drilling multiple holes through framing members

Originally posted by apauling:
Drilling neat and exact holes along any height (at the same height) will weaken the wall more than erratic drilling. It creates, in effect, a controlled joint where the wall will fail, similar to a controlled weak point as a control joint in concrete.
Before my joke: That makes a lot of sense! Brilliant!

My joke: See, my crappy drilling was right all along! :)
 

tstern

Member
Re: Drilling multiple holes through framing members

Roland,
I may suggest to drill a larger hole, say a 7/8" and run two NMs thru each hole to cut in half the amount of holes drilled. Less holes are better for the integrity of the bearing wall.
---------------
TS
 

rolanday

Member
Re: Drilling multiple holes through framing members

All, thank you very much for the information and advice -- very informative and helpful.
 
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