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Drilling holes in floor joists

replying to Joe, Dot wrote: Hi there we need to vent a new bathroom in basement and want to know if you can drill a 4" hole in the floor joist just above the concrete foundation.. Tks

Reply to
Dot
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If you mean the "rim joist" then yes, you can drill a 4" hole in it. If you mean a *floor* joist, then no, not without replacing the structural support in some manner. There are specific codes for how to bore and notch floor joists.

Placement in the rim joist should done carefully to ensure you aren't removing structure where you shouldn't, like under a door opening, jack stud, etc.

DAGS 'vent in rim joist' or something similar. You"ll get lots of hits and tips.

Reply to
DerbyDad03

Depends on the size of the joist. If it's a 2x10, then a 4" diameter is a no no. If it's a 2x12, then yes, but must be dead center from top to bottom and more than 6" away from ends.

Reply to
Meanie

Cite please? Not arguing, just looking for the correct answer for the OP.

You did see that my answer including the words "If you mean rim joist", right?

A rim joist is (should be) supported along it's entire length either by either the foundation or (hopefully) a sill plate. AFAIK the size of notches and holes allowed in rim joists exceed the size of notches and holes in spanning joists.

Reply to
DerbyDad03

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Holes: Do not bore holes closer than 2" from joist edges, nor make them larger than 1/3 the depth of the joist.

Notches: Do not make notches in the middle third of the span where the bending forces are greatest. Notches should be no deeper than 1/6 the depth of the joist. Notches at the end of the joist should be no deeper than 1/4 the depth. Limit the length of notches to 1/3 of the joist?s depth.

So, by computation since a nominal 2x12 is actually 11-1/2", the max diameter is 3.83333" which accommodates a 3-3/4" but not full 4".

Reply to
dpb

I had already seen that document. Let's look at the title:

NOTCHING & BORING GUIDE FOR *FLOOR JOISTS* & STUD WALLS IN CONVENTIONAL LIGHT-FRAME CONSTRUCTION

I asked for a cite related to notching and boring *rim joists* (or band joists) mainly because I am unable to find one. I can find a lot of anecdotal posts claiming that the same rules don't apply to rim joists and that matches up with what I have always understood.

Even the IBC seems to distinguish between "joists" and "rim/band joists" giving the impression that the same rules don't apply.

They say here that there is an exception for how "joists" are must be supported when they are attached to a "rim joist", which leads the reader (me) to feel that when they use the one-word term "joist" they are *not* talking about rim joists.

Note the word "span" at the end of the following paragraph. I've never heard "span" used in reference to rim joists, which once again leads the reader (me) to feel that any use of the word single word "joist" refers to spanning joists, not rim joists.

IBC 2308.8.2 Framing details.

Joists shall be supported laterally at the ends and at each support by soli d blocking except where the ends of the joists are nailed to a header, band or rim joist or to an adjoining stud or by other means. Solid blocking sha ll not be less than 2 inches (51mm) in thickness and the full depth of the joist. Notches on the ends of joists shall not exceed one-fourth the joist depth. Holes bored in joists shall not be within 2 inches (51 mm) of the to p or bottom of the joist, and the diameter of any such hole shall not excee d one-third the depth of the joist. Notches in the top or bottom of joists shall not exceed one-sixth the depth and shall not be located in the middle third of the span.

Reply to
DerbyDad03

The quote I saw was attributed to Meanie asking for a quote that was related as it appeared at that point as being bearing joists. That was all I responded to.

Since rim joists are fully supported, there's no such load-bearing issues on them; the most there can be is a very concentrated point load that could conceivably crush a local position if a very large fraction of the material were removed, but even that would be quite difficult in practice since one would presume the sill plate above would still be in place to distribute load.

Hence, I'm quite confident the rules do _not_ apply; without access to a full copy of IBC/UBC don't have a clue as to where to find any actual data; that one is about as tough to find an open-source copy of as anything ever searched for...

Reply to
dpb

I believe that you and I are on the same page, but we have to go all the way back to the OP and my initial response, which is what Meanie responded to.

Meanie's response to my response seems to indicate that he thinks it depends

*only* on the size of the joist. Note the paragraph that he quoted. I made a distinction being floor joists and rim joists, Meanie did not. That's why I asked for a cite. I was looking for a cite that states that a joist is a joist is a joist. As you and I know, they are not.
Reply to
DerbyDad03

You are correct, a rim joist is not a floor joist and a 4" hole or bigger i fine. My response was in relation to the floor joist answer as I indicated if it were a 2x12 compared to 2x10. Though, dpb made a great point about nominal size and thus, a 4" dia would be too big for a 2x12 due to it's actual size. In addition, he also stated the proper rules which is cited here....

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Reply to
Meanie

...which I already knew. My point to you was that it's not just about the size of the wood "Depends on the size of the joist". It's *first* about which type of "joist" we are talking about (which is why I made that distinction in my response to the OP) and *then* about the size.

Based on how your response came across, I was asking for a cite on the boring limits of a rim joist.

It sounds like we are all in agreement now, although we don't know with

100% certainty that the OP is talking about the rim joist. ;-)
Reply to
DerbyDad03

The way I read it, he was only refering to the size of hole in the "joist" joists, not the "rim" joist and was clarifying that the size of hole allowed was determined by the joist size. I thought it was pretty clear.

Reply to
clare

Given that it's a vent for a basement bath, what are the odds that the poster is really talking about a rim joist? If he is, then I guess the vent pipe is going up the outside wall of the house?

Reply to
trader_4

He said bath*room*, not bath.

I took "vent a new bathroom" to mean he needs to install an exhaust fan, not a plumbing vent.

Reply to
DerbyDad03

K, I took it as a plumbing vent. If it is a fan vent, then I agree, the rim joist hole makes sense and maybe you're right. I think there are fans that will work with 3" too, so that could be a choice for a smaller hole. Especially if the duct is short distance, 3" could be fine.

Reply to
trader_4

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