# Hole Diameter Size In Floor Joist for Data Cable



## Breakingcustom (Mar 17, 2010)

I'm about to start running data cable to the rest of my house through the basement ceiling (got tired of the attic). 

My floor joists are 2x8 (7 1/2" measured) and are spaced 16" on center. Wherever their is a wall, there are floor joists 6" on center (only 3 of them).

I have a ton of cables to run through and I thought I saw that you can drill a hole a max 1/3 the size of the actual measurement of your floor joists. So if my math is I can drill a 2 1/2 hole in a 2x8 floor joists that measures actually 7 1/2".

Am I correct with this statement?


----------



## Thadius856 (Jun 2, 2011)

Can't comment as to the largest safe size.

However, I can tell you that a 3/8" hole can fit 1-2 ethernet cables and a 3/4" hole can fit 4-5 cables. I would consider using multiple holes of these two sizes, as they're standard sizes for cable bits (which you may want to invest in).


----------



## Breakingcustom (Mar 17, 2010)

I need to setup reminders when people reply. I have a Milwaukee self-bid set for my Milwauke right angle that I used a 2 1/8" bit. The thing is I'm going to have 20 something cables coming through this hole (Cat6 and Coax).


----------



## AndyGump (Sep 26, 2010)

*R502.8 Drilling and notching.* Structural floor members shall not be cut, bored or notched in excess of the limitations specified in this section. See Figure R502.8. 














For SI: 1 inch = 25.4 mm. *
FIGURE R502.8 CUTTING, NOTCHING AND DRILLING

This may help you.

IRC 2009.

Andy.
*


----------



## bubbler (Oct 18, 2010)

Just for the sake of saying it... have you considered fastening them to the ends of the joists? (I'm assuming this is an unfinished basement since you're talking about drilling holes in joists).

What I did was buy a few dozen velcro ties. I stapled them along the joist face/ends where I needed. Then I was able to bundle all the cables I needed and velcro them together. 

1) You aren't putting holes in structural framing members of your home
2) Replacing or adding a cable can be easier--particularly adding if you're at max capacity for whatever holes you've drilled
3) With the velco ties, there is no worry about a pinching the cables (not really an issue for you with the drilled holes, but would be if you were using staples or zip ties to secure anywhere)
4) You can create larger sweeping arcs when turning corners (vs. turning within the ~14" between the joists); this can be helpful depending on what cables you're running.

When running parallel to the joists I found that those red plastic clips for holding multiple NM electrical wires worked great. I put them every ~20" or so and was able to drop my cat5e and coax into them, it looks quite neat and was very easy to install. Easy to change out or add cable as well.

I ran straight lines and away from any power, it looks fairly good to me, and it's no worse, in terms of lost headroom, than the heating and plumbing pipes which are run on the face of the joists in my home.


----------



## Breakingcustom (Mar 17, 2010)

My joists run from front to back of the house. So to get to the the outlets in my bedrooms I will have to run them through the joists. I would've just went through the attic, but I recently blew in more insulation so it would be a pain moving all the insulation away from where I would need to drill my hole.

When you say at the ends there is no way for me to do this because the ends of the joists go from front to back and there is no gap.


----------



## Breakingcustom (Mar 17, 2010)

AndyGump said:


> *R502.8 Drilling and notching.* Structural floor members shall not be cut, bored or notched in excess of the limitations specified in this section. See Figure R502.8.
> 
> 
> 
> ...



Yeah I came across that the max diameter of the hole is 1/3 of the actual depth of your joist. I measured mine and they are 7 1/2in so according to that I can use a 2 1/2in hole.


----------



## Thadius856 (Jun 2, 2011)

Out of curiosity, does this figure apply to a stem wall also?


----------



## gregzoll (Dec 25, 2006)

First off, what is a ton of data cables. For how long I have done data networking, ton does not factor in on the number of cables. Now, bundle, ports, lines, do. How many Cat-5e or Cat-6 do you plan on running back to where the patch panel is going to be?

If only going to pull 14 cables, you can get by with two maybe three 3/4 holes. If it was me, and I was doing it, I would just mount a 1x3 or 1x4 and run the cables along that, vs pulling through holes in the joists.


----------



## Breakingcustom (Mar 17, 2010)

When Im fully finished I will have around 48 network drops and not even sure the # of coax. The upstairs as 18 data drops and 13 coax drops. I haven't even started the basement remodel yet.

I'm not getting where you are saying putting in a 1x3 or 1x4? I have to pull through the joists no matter what in my basement to get to certain locations. Like I mentioned the floor joists run from front to back of the house with no gaps at the ends. Drywall will be flushed to the floor joists so in order for me to run wire in the living area of the basement it has to go through the joists. I can't run anything through the studs because I'm ripping all of those out at some point and putting in 2x4's when the basement remodel actually starts. I'm just wanting to get the entire upstairs terminated and ran.

Also, there is no way you could get that many cables in 2 3/4" holes. The fill ratio for a 3/4" conduit is 2 Cat6 cables without a divider. I know you can also put more in, but I've done structured cabling for a few years before moving into IT and I remember trying to pull cables through 3/4" conduit. You are lucky to get 4 if you have bends.


----------



## JohnFRWhipple (Jun 3, 2010)

I would never notch the top or bottom of any floor joist and am not sure if that detail is correct for any Canadian building code.

Do not drill your hole within 2" of the top or bottom either.

It would be far safer to drill 2 double 1 1/2" holes.

I would check the span tables as well before drilling to ensure that the framing members are even the right size before weakening them further with large format holes.

JW


----------



## Breakingcustom (Mar 17, 2010)

JohnFRWhipple said:


> I would never notch the top or bottom of any floor joist and am not sure if that detail is correct for any Canadian building code.
> 
> Do not drill your hole within 2" of the top or bottom either.
> 
> ...


I'm not notching the floor joists. I'll probably just go with doing 2 1/2 holes although I already did drill on 2" hole already, but no worries. I have to drill through like 15 floor joists to get to the other side of my house, but luckily I just bought a Milwaukee right angle drill.

Your speaking Chinese to me with span tables and what not. I know the joists are 2x8 (not the actual size though and not sure grade of lumber) and are spaced 16" OC. The house is about 20' ft from front to back and there is the main support about half way between.


----------



## Duckweather (Mar 26, 2012)

From a structural engineer on one job, draw a line from the bottom of the joist, at the bearing end, to the top of the joist in the center of the span, then back to the bottom at the other end. That triangle bears most of the weight. Never drill below those lines. Shear strength at the end is much greater than bending strength toward the center. It is better to stay close to the end. Top and bottom should never be notched because they are under compression, (top), and stress (bottom). That is why trusses and engineered joists work, because of rigidity not size of components. That is simplified rule of thumb, not a valid computation.


----------



## gregzoll (Dec 25, 2006)

You can put more than two Cat-5e or Cat-6 into a 3/4" hole. Who ever told you that you couldn't is full of it. As for your intent, 48 cables is a lot of pulls, and personally, I would split it to multiple holes at no larger than 1" max, 5/8 would be better. Remember, this is not a commercial application, this is a residential structure.

As for coax & data, keep coax on its own, data on its own, and keep a plan of what runs where. BTW, you can easily run 7 maybe 8 cat-5e or cat-6 max in a 1/2" hole, which is what I have down in my basement. A 3/4" hole would allow you to run at least 12 data, maybe 6 coax per hole.


----------



## Breakingcustom (Mar 17, 2010)

I'm not running standard Cat6 cable. I got leftover cable from a project and it is all Panduit Cat6 plenum so it's not as small as regular Cat5e.


----------



## tony.g (Apr 15, 2012)

Breakingcustom said:


> Your speaking Chinese to me with span tables and what not.


He was advising you on a critical factor to be taken int account when drilling or notching joists which may already be near their safe-span limit.


----------



## gregzoll (Dec 25, 2006)

Breakingcustom said:


> I'm not running standard Cat6 cable. I got leftover cable from a project and it is all Panduit Cat6 plenum so it's not as small as regular Cat5e.


It is not that much larger. Run bundles of at least six per 5/8 hole, and you will do fine. I sure would not pull one large bundle, and end up with a two inch hole, which would be unprofessional way of doing it.


----------



## dalepres (Mar 20, 2011)

I'd consider a more distributed network design. Add a switch here, a switch there, and significantly reduce the number of wires to run.


----------



## gregzoll (Dec 25, 2006)

dalepres said:


> I'd consider a more distributed network design. Add a switch here, a switch there, and significantly reduce the number of wires to run.


That is not how to properly do a distributed network design. What the OP is doing, is how it is commonly done. Only time you would put a switch here or there, is if you have a large network spanning multiple floors. Then you want to use smart switches and patch panels on each floor, then run a backbone down to the main network equipment room.


----------



## dalepres (Mar 20, 2011)

Actually it is how to design a network. I am a network engineer and have done this many, many times, in businesses and in homes. In a business scenario, you need smart switches and patch panels. You can install one per floor, or you can install one for multiple floors or one per seating area that might support a handful of folks. It just all depends on the layout of the building, difficulty in running wires, length of cables, distance between buildings, etc.

In a residential scenario, you don't need smart switches at all. Simple 50 dollar gigabit switches installed in each "zone" of the house would be perfect. Using smart (or managed) switches at home does not make sense at all. While a home-run wiring with a patch panel would give a look that you could show off how cool and industrial looking your network room is, there is no technical advantage to that. You can simply plug directly into the switch. That would mean, assuming 8-port switches, a maximum of 8 cables in any single run. This is much more structurally friendly to the house.


----------



## gregzoll (Dec 25, 2006)

The OP is not going to just do networking, it is for structured A/V controls along with hdmi for remote equipment with hdtvs. May want to read the beginning, then just jump in with a different idea.

Yes there are various ways of doing things, but your idea does not work for this job.


----------

