We need to run some 12/2 Romex through the floor joists of a newly built home. Can we drill the floor joists wherever we see fit, or are there limits?

I should have been a bit more clear with my question. My concern, and the disagreement with the SO, is where along the length of the joist can we drill? Does it need to be in the outer thirds of the span, leaving the middle span untouched?

Now that you say that, I recall hearing it before.

In checking it out, I see that the "rule of thumb" is actually to go through the middle third.

After finding this article (http://muextension.missouri.edu/explore/agguides/forestry/g05560.htm), the next 3 I found confirmed the same thing:

When possible, drill through the joist with the smallest bit necessary to allow passage of the pipe or wire. Confine the drilling to the center line of the center third of the board

There are some requirements on spacing the wires too. Searching tkrussel's posts in electrical and lighting may turn them up. If you don't find them, post the question there. Nobody here gives better answers on electrical stuff.

I am surprised by the website rickj found, which states the wiring must be confined through the center third of the span of joist. This is not how it is done in the real world.

Unfortunately , I do not have a BOCA or IBC, building codes handy to be able to quote exactly the code article or section. I can tell you as being in the indusrty over 30 years, the recommended location of drilling any hole in the center third is just not done, or allowed.

The National Electric Code does not address this issue, only building codes, due to structural integrity of the framing members.

NEC only addresses the location of a hole from the edge of a member, must be at least 1-1/4" away from the top or bottom edge, to prevent a nail or screw from being driven into the wiring.

Think about it... as I believe you have realized.. the center of any span of a framing member is the area of weakest, where there will be the greatest bending and flexing. Any hole in this location shall compromise the strength.

Imagine drilling holes only in the center third of a bridge, where the strength must be the greatest to counter act the down ward forces of weight being loaded on it. I will be swimming across the river before I wlak across that bridge.

We are not allowed to drill holes for any wiring in the center third of a floor joist, all holes for wiring must be in either or both of the outer thirds of a span, as you seem to already be aware of.

Since the actual codes are not available on the internet, I have only been able to find various forums to back my claim.

Since you are wiring your new home, you should be applying for a permit to wire, and you can certainly check me with your local electrical and/or building inspector.

Thanks for your replies.

I told Dan to run it down the side- but no... He should use his own name to post, doncha think?

Anyway: Drilling a 1/2 inch hole in any part of the span- given using the vertical, top to bottom center third is OK as long as you do not notch a joist in any part of the center third (horizontally). We asked the Bldg Inspector about the 1/2 inch hole. I doubt it would ever be acceptable to drill a large hole in the center center. Notching is right out.

I know it is confusing- but it does make sense to avoid the horizontally measured center third of the span as a general rule.

If I understand you correctly, your inspector said to drill your holes in the center, right? Then there you go, hope you got that in writing, or by his acceptance of the installation is approval of this method.

I will not be drilling holes in the center third of the span ,measured horizontally, however.

Driling a hole in the center of the vertical is fine, as I stated the NEC only limits you to 1-1/4" from the top and bottom edges.

Didn't you post some rules for how far a hole needs to be from the next wire?

OK, so I wasn't registered and used my wife's name to post. So sue me.

The interesting thing is that when I Googled "drilling a floor joist" one of the forums said to limit the holes to the center third, and leave the last foot at either end alone.

I don't know what we'll have to do if the inspector decides to be a jerk and say we can't do it after it has been done. Replace the joist?

Well what it comes down to is "What your inspector says."

Now the other problem with this question is what type of lumber are you talking about? Main beams are often built using Microlams. Other joists may be normal 2x4 material or engineered TJI beams. The manufactuarer specs can be found by contacting them. But they are all different. We work in various municipalities and the rules vary based on both location and the inspector (Yes the inspoector can't make his own rules, but its bad to argue unless pressed). In one place for example the microlams may only be drilled once! That's one hole not to be in the middle third of a span. So if the plumber gets there first we need to run wires roundabout.

You should follow manufacturer specs when drilling any manufactured beam or laminate product. Typical joists should be drilled in the center 1/3. Someone made the comment that this isn't the real world. As a licensed home inspector I come across many of the "real world" situations. There is a right way and a wrong way. It may take a little more time and money to do it right. That is why many builders and subs take short cuts and someone else has to pay to redo the job the right way. And just because it gets by the "code" inspector doesn't mean that it was done correctly. The code inspectors are usually overworked and underpaid and have many sites to visit and only so much time to do it. They can't see everything.

The 2003 International Residential Code covers this:
Not exceeding 8 feet (2438 mm).
R502.8Drilling and notching. Structural floor members shall
Not be cut, bored or notched in excess of the limitations speci-
Fied in this section. See Figure R502.8.
R502.8.1 Sawn lumber. Notches in solid lumber joists, raf-
Ters 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 teres shall not exceed
One-fourth the depth of the member. The tension side of
Members 4 inches (102 mm) or greater in nominal thickness
Shall not be notched except at the ends of the members. The
Diameter of holes bored or cut into member shall not exceed
One-third the depth of the member. Holes shall not be closer
Than 2 inches (51 mm) to the top or into member 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 (51
Mm) 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.
R602.6Drilling and notching—studs.Any stud in laminated members
Wall or bearing partition may be cut or notched to a depth not
Exceeding 25 percent of its width. Studs in non bearing parti-
Tions may be notched to a depth not to exceed 40 percent 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 width, the edge of the hole is no closer than 5/8
Inch (15.9 mm) to the edge of the stud, and the hole is not lo-
Cated in the same section as a cut or notch. See Figures
R602.6(1) and R602.6(2).
Exceptions:
1. A stud may be bored to a diameter not exceeding 60
Percent of its width, provided that such studs located
In exterior walls or bearing partitions are doubled and
That not more than two successive studs are bored.
2. Approved stud shoes may be used when installed in
Accordance with the manufacturer’s recommenda-
Tion.
R602.6.1 Drilling and notching of top plate.When piping
Or ductwork is placed in or partly in an exterior wall or interior-
Or load-bearing wall, necessitating cutting, drilling or notch-
Ing of the top plate by more than 50 percent of its width, a
Galvanized metal tie of not less than 0.054 inches thick
(1.37mm) (16ga) and 11/2 inches (38mm) wide shall be fas-
Tened to each plate across and to each side of the opening
With not less than eight 16d nails at each side or equivalent.
See Figure R602.6.1.
Exception:When the entire side of the wall with the notch
Or cut is covered by wood structural panel sheathing.

R802.7 Cutting and notching. Structural roof members shall
Not be cut, bored or notched in excess of the limitations speci-
Fied in this section.
R802.7.1 Sawn lumber. Notches in solid lumber joists, raf-
Ters 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 (102 mm) or greater in nominal thickness
Shall not be notched except at the ends of the members. The
Diameter of the holes bored or cut into members shall not ex-
Ceed one-third the depth of the member. Holes shall not be
Closer than 2 inches (51mm)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 (51 mm) 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 (102
Mm) and the length of the cantilever does not exceed 24
Inches (610 mm).
R802.7.2 Engineered wood products. Cuts, notches and
Holes bored in laminated veneer lumber, glue-laminated
Members or I-joists are not permitted unless the effect of
Such penetrations are specifically considered in the design of
The member.
R802.10.4 Alterations to trusses. Truss members shall not
Be cut, notched, drilled, spliced or otherwise altered in any
Way without the approval of a registered design professional.
Alterations resulting in the addition of load (e.g. HVAC
Equipment, water heater) that exceeds the design load for the
Truss shall not be permitted without verification that the truss
Is capable of supporting such additional loading.

Drilling joists to run wiring. A clear code violation. What is the inspector thinking?
Run the 12/2 down the joist to the wall and along the wall. If not you should install some EMT along the bottom of the floor joist to run the 12/2. 12/2 indicates an outside supply so you may want to run it in PVC instead.

Can you provide that actual code Article and Section that states that drilling wood framing members is not allowed?

Sorry, I should be saying, "what was I thinking". Cables of any size may be run through bored holes in joists in unfinished basements.

THis should answer everything you need to know
Notching a Joist | Framing | How-to | This Old House (http://www.thisoldhouse.com/toh/asktoh/question/0,,1582745,00.html)

We need to run some 12/2 Romex through the floor joists of a newly built home. Can we drill the floor joists wherever we see fit, or are there limits?
Yes you can .but you can not drill the upper third or lowwer third!

Law and Daisy, did either of you notice this post is 2 years old?

We need to run some 12/2 Romex through the floor joists of a newly built home. Can we drill the floor joists wherever we see fit, or are there limits?
1st you need to check with local building inspection dept for your jurisdiction. There are specific limits - and for good reason: you are potentially changing the structural integrity of the lumber. It may even be listed on line if the local community has uploaded their codes. Do not just follow someone else advise. Find out what is appropriate and permitted for your community.

Saratogans, Law and Daisy, did any of you notice this post is 2 years old?

What I have learned here is that I still don't know the answer.

The illustration at this link really cuts through the fog..

How To Drill Through Floor Joists | thefamilyhandyman.com (http://www.rd.com/familyhandyman/content/75390/)

Holes that are no more than 1/3 of the joist depth can occur anywhere along the joist provided that larger holes are centered along the long axis and all holes are away from the edges. Vertical shear forces are strongest at the bearing points. This condition is generally handled with additional material, so think about what's going on above before drilling a large hole here, better not to. Where horizontal tension and compression forces are greatest i.e in the center third of the span NO NOTCHING should occur.

I'm no expert ( I did sell building materials a long time ago) however this question did jog my memory. As I recall, I believe the load bearing in a joist is done mostly toward the ends and diminishes as you approach the center. To picture this imagine the joist with a shape of a long football drawn on it from end to end. The area outside the football is the load bearing area of the joist, the area inside the football carries less if any load depending upon the construction. For example engineered I-beam joists have perforated knock-outs for running wire as well as duct within (in the web) but not but not outside of this football shaped area.

I'm not an expert either.. but as far as my understanding goes you are on the right track "onedayold".. be careful when using the term "load". There are lots of kinds of "loads". If you are referring to "shear load".. that increases as you approach the bearing points.. imagine the difference between having someone step on your arm on a flat surface (shear above is localized at the foot but gets a little more spread out below)... or with your arm resting on a brick (shear is localized above and below).. the pain with the brick would be different and the more the muscle the less pain.. therefore shear tends to be handled with additional material. "shear" can crush or punch through... other "loads" that spans can havel.. the "smile" that a simply loaded beam (supported at either end) assumes is from deflection.. pretty much handled by compression above and tension below.. this is more a question of vectors and geometry.. disrupt the geometry at your peril... too much "deflection" can snap a beam like a broken twig.. it can also raise heck with windows and doors... "bending", that other "load" is a little hard to explain but engineers seem to like to compare it to "loaded taffy".. not a smile, more like a stretched out upside down omega shape in a beam under simple loading.. this can be a big problem... other loads include "impact" like when you suddenly drop a piano on the beam.. "thermal" causing expansion and contraction etc.. etc..

Anyway.. the football shape sounds pretty good as an illustration of where the work is being done as far as the material is concerned.

OneDayOld and Jsquared, You both have Just enough knowledge to be dangerous. The shear stress in the joist is maximum at the ends and goes to zero at the center. The bending stress is maximum at the center and goes to zero at the ends. The bending stress is resisted by the top and bottom of the joist whereas the shear stress is resisted by the whole depth of the joist. A 3/4" hole centered in a 10 inch floor joist is not going to get you in trouble but if you hack away at your floor support structure without knowing what you are doing... Go find a structural engineer.

ScarboroughME.. a structural engineer distinguishes between bending stress and deflection. bending stress is dependent upon the strength of the material and the location and degree of load points above and below... not necessarily at mid point. The danger is assuming that it is always at midpoint. What happens when a piano gets moved? Or a lot of people start dancing at a party?

The handyman website that I sited on Jul 21, 2008, 03:23 PM does a pretty good job of explaining how to keep out of danger.

What's with the condescending tone? Who was talking about 3/4" holes? And what was inaccurate?

Jsquared, I apologize if I sounded condescending. I meant no disrespect. I only mentioned the structural engineer as a solution to a complicated problem. You are absolutely correct that points of maximum shear and bending can vary depending on the application of load. What I described was the stress distribution for a joist loaded uniformly over its entire length. I mentioned a ¾” hole because the string started with the task of routing “some 12/2 Romex” and it would be hard to get into trouble with a small hole.
Again, sorry to have offended you.

ScarboroughME

It says a lot about this issue that the thread is so old.. you are to be commended for actually going back to the original question. I had forgotten the 12/2 romex.

Having enjoyed the framing modifications made by certain plumbers through the years (not all plumbers don't get mad out there some of you are friends of mine), I believe that this question should be more widely understood by one and all. The long term state of things found beneath bathrooms during demolition can be shocking.. and a tribute to the resilience of light frame construction. As engineered products capable of very long spans become more commonplace someone should come up with a rhyme or something to help us all get it right.

Thanks for the gracious reply

From an engineers perspective, the bottom center of the joist is the area of the joist seeing the greatest tensile (pulling apart) force. Drilling a hole in this location should be avoided because it could significantly reduce the overall structural capacity of the joist (and if drilled through several spans, the overall structural capacity of the floor itself). The bottom half of the outer 1/3 of the joist over the span is primarily undergoing compressive (pushing together) forces. The floor joist would be better suited to have holes drilled in the portion experiencing compressive forces rather than in areas where tensile strength in the joist is required. The buckling capacity of the beam is affected less by the holes drilled in the compressive portion than the structural capacity of the joist would be affected by the holes in the area under tension. If you would draw a sine type wave from the top area of one end of the beam, dipping down along the bottom center of the beam and then back up toward the top portion of the beam at the other end... drilling above all areas above that line should be avoided. That leaves the bottom outer third on each end for use to drill for placement of wiring.

I Think oldmanspoon answered the question?. ITS CODE right?;)

oldmanspoon

Jun 28, 2006, 07:23 PM
The 2003 International Residential Code covers this:
Not exceeding 8 feet (2438 mm).
R502.8Drilling and notching. Structural floor members shall
Not be cut, bored or notched in excess of the limitations speci-
Fied in this section. See Figure R502.8.
R502.8.1 Sawn lumber. Notches in solid lumber joists, raf-
Ters 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.