We are installing a Panasonic vent in our basement bathroom. Need to run a 3″ duct through 2 joists to get to the outside wall outlet which is already in place. Electrician is coming next week to do the hook-up with all the electric, so we’d like that in place for him.
Question: We need to either notch the 2×10’s by 3/4″ at the bottom of the joist, or drill a 3″ hole through the middle of the two joists. These holes would be about 3′ from the outside wall, with a 15′ run total. My guess is either would be ok, but is one markedly better than the other?
Thanks!
Replies
>> We need to either notch the 2x10's by 3/4" at the bottom of the joist, or drill a 3" hole through the middle of the two joists.My guess is either would be ok, but is one markedly better than the other? <<
You can't notch the bottom of the joist. You can drill a 3" hole in two joists where I'm from. Make sure your no less than 2" up from the bottom of the joists. Go in the center if you can.
Joe,I've got a follow up on this if you don't mind. Does this mean no notching anywhere on the bottom of the joist? Reason I ask is that most of mine are notched a 1/4 inch where they sit on the center I beam. No notches where they sit on the sill, just in the center of the house. Just curious.Thanks,
SteveTua res agitur, paries cum proximus ardet ~ Horace
This gives you the max notching and holes for joist and studs.http://www.codecheck.com/pg03_04building.html#fb8notching.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Thanks Bill,Didn't realize Code Check had a version for framing. That's a nice resource. Thanks for the link.Best,
SteveTua res agitur, paries cum proximus ardet ~ Horace
Well, in the end my husband and I decided to run the duct work parallel to the joist, and we're going to cut a new hole in the exterior wall. That solves two problems; no new holes in the joists, plus no turns in the ductwork. Why didn't we do that first? Well, it's a remodel, and we were trying to reach the outside vent already in place from the old bathroom. If we drill holes in the joists to run the vent lines, we will have to relocate water supply lines, and the vent will end up going upwards and then downwards - with all the moisture in a basement bathroom that doesn't seem wise. Plus, this house was custom built in the 60's. The joists are vertical grain Doug Fir, and even drilling small holes in them is a challenge. Again, I salute you remodelers!! Thanks again for your input!Ann
Steve,
That 1/4" notch was to plane the joists/ceiling or the floor above. Not a problem as far as structure.
Chuck Slive, work, build, ...better with wood
Thanks Chuck,I thought that would be the answer, but you know what happens when you assume, right :)Besides with the nest of electrical and plumbing screw-ups I've uncovered, that wouldn't have been a great surprise to discover issues with the framing as well. Glad to know that's not the case. And to be fair, I think most of the mess came after the original construction.Best,
SteveTua res agitur, paries cum proximus ardet ~ Horace
Speaking of drilling and notching joists, check out the attached pic. This is another builder.... and it looks like the holes were done by the supplier of the joists so I think they are compliant with the I-joist manufacturer's requirements... but MAN!!! - it seems that common sense alludes some people...
What do you think?
That is scary, and there is more than one run of holes. TO the right there is another set of them.
Someday people will realize that if you pour 9' basement walls you can run all your mecahicals under the joists and still have at least an 8' ceiling.
Two things tend to make those holes reasonable:- These are I-joists, so the bulk of the strength is in the flanges. The web primarily serves to hold the flanges the proper distance apart.- The holes are circular, and there is only a very small length of the flange that is effectively web-less. This means that there is very little impact on the joist's ability to resist buckling in the upper (compression) flange and similarly very little impact on the web's ability to hold the flanges apart.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Well - maybe.... but I wouldn't build my house that way... sometimes you gotta do what ya gotta do, but I don't think I'd use the word "reasonable" to describe it. Maybe "necessary" or "workable" would be a words I'd use...
I'd like to get BossHog's thoughts on it.
Boss:
got any thoughts on the pic I posted a few posts back on this thread?
I'd have to look at my charts at work tomorrow, but I don't think that's allowable.I can MAYBE believe that one hole that big might be allowable at the center of the span. ButI don't think 2 holes in one span would fly.At least they didn't cut into the flanges...
What is the white man's greatest contribution to the world? Blondes. [Adam Rifkin]
I started doing some Googling for mfg recomendations and found
this Georgia Pacific page. Check out this link WIDE OPEN™ Wood I Beam™ Joist (463KB/2pgs) to see precut I-joists. And the product guide Engineered Lumber Floor and Roof Systems Product Guide (2MB/56pgs) does allow such big holes. It says holes can go no closer than 1/8" to the flange.
and here is some info for one of the LP series I-joists. And another. It says no closer than 1/4" to the flange, but also allows big round holes.
Like I said initially, I think what they did is allowable. I still don't like the idea of cutting that many large holes in a line across the whole floor system... From a practical standpoint, it seems that it would have to weaken the floor system. Maybe produce more bounce. For example, I think many of us know what happens when you take a joist span table and max out your installation - even though it is still "allowable". I guess we are all here to learn though...
I checked out the GP hole chart this morning for 11 7/8" I-joists. It's attached to this post.It shows a max allowable diameter of 8 5/8" for a hole, so what was done in this case wouldn't fly.There may be situations where large holes will be O.K. - It depends on the span of the joists, spacing, and where you want to put it. The engineering department of the I-joist manufacturer will review special cases on request.
My mind-set is Munich. Most of my generation's is Vietnam. [Madeleine Albright]
Lessee -- my recollection is that the flange on a 11-7/8 I-joist is maybe 1-1/4". So two flanges off of 11-7/8 leaves 9-3/8" of exposed web. An 8-5/8" hole in a 9-3/8" web would leave a total of 3/4" of web, or 3/8" on each side if the hole is centered.From the pictures you'd be hard-pressed to determine that there isn't 3/8" of flange either side of the hole.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
You're right, but -The chart allowed ROUND holes. The picture shows oblong ones. So I still dno't think they're kosher.
I'm going to start a museum where all the work has been done by children. I'll put all the paintings up on refrigerators.
I doubt that they're oblong -- awfully hard to cut a clean oblong hole. I think that its primarily the viewing angle that makes them look oblong.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
It's true that the bending strength is in the flanges but such a large hole in the web like that destroys the shear strength and I suspect that BH is right that these holes are not allowed by the product manufacturer except (possibly, as he states) at the mid span.
Of course, we can't see the other end of the span so maybe these holes comply.
We await BH update.
Framer's right. Drill the hole in the middle third of the joist from top to bottom and the outer third of the span and you'll be within code guidelines. Never notch the bottom of a joist.
Joe Carola says try to locate in the middle of the span. You say locate the hole in the outer third of the span. Aren't those parameters opposite? Perhaps you mis-stated what you intended (or I mis-understand).
A hole will affect the shear capacity of the joist. For uniformly loaded simple span joists, the shear is lower in the middle portion of the span. Shear is higher toward the ends of the span. For this reason, it would normally be better to locate a hole toward the middle portion of the span.
I think Joe said to drill in the middle of the joist from top to bottom, ptp was referring to its location on the span of the joist. The hole is best located at about a third of the joist length to avoid the shear at the ends and the bending in the middle.
"Joe Carola says try to locate in the middle of the span. You say locate the hole in the outer third of the span. Aren't those parameters opposite? Perhaps you mis-stated what you intended (or I mis-understand)."Locate the hole in one of the outer thirds of the span and in the middle third of the height of the joist. Take a look at the diagram attached. Hopefully it is clear enough to read.
OK, here's the diagram.
I saw the diagram and I've read your posts.
Perhaps you are not distinguishing between notches and holes. I am and I stand by me previous posts regarding this.
The diagram says nothing about holes in the middle third or outer third or at the third point of the span. I realize you (or someone) said this is a common practice and I understand the reasoning stated but I don't fully agree with the reasoning. I am saying that; regarding holes, the affect on bending is minimal if done correctly and the affect on shear strength more significant and therefor, it is best to locate the hole within the mid span of a joist.
We don't disagree about notches
Good to see you back around, where ya been? What you get is what you see, These things don't come easily.
Hmmm... it does say "no notches permitted." I guess that I never noticed that it made a distinction as I've been taught not to drill or cut a joist in midspan. If holes are allowed anywhere on the span, it certainly opens more possibilities for easier routing of pipes and wires. Thanks for pointing that out.
Truss joists holes are always at least 2' away from the bearing point, so I would agree. As far as drilling convention lumber, I avoid it. If you have to, I glue and screw 3/4" plywood gussets and then drill the whole mess (no pun intended). Maybe overkill, but cheap insurance at this point. Plus helps me to sleep at night.
To be technically correct, you can drill a 3 1/6" hole in a 1.5" x 9.5" (2x10) joist.
What is the outside Dia of your 3" duct"?
Can you transition from round to oval or rectangle to go under the joists without notching? Structurally, this is best.
SamT
Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. [Einstein] Tks, BossHogg.
It's probably in the 3 and 1/6 " range. So, we'll work from that and see about cutting a hole in the joist. Honestly, remodeling with existing work in place is no fun at all! I don't see how you guys do it job after job!!
cd, thanks.
Honestly, remodeling with existing work in place is no fun at all! I don't see how you guys do it job after job!!
A great place for Information, Comraderie, and a sucker punch.
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
Can you just drop the whole ceiling? That is what I did in my main floor bath in order to get the exhaust fan ducting out to the side of the room. I just framed below the exising joists with 2X6 going in the opposite direction to the existing joists. The ducting ran out between the new 2X6's to a chimney chase at the end of the bath and then up through the 2nd floor into the attic and then turned and went out through the gable end. I expect most folks never notice that the ceiling in the bath is a bit lower than in the rest of the house.
Randy
>> Can you just drop the whole ceiling? That is what I did in my main floor bath in order to get the exhaust fan ducting out to the side of the room. I just framed below the exising joists with 2X6 going in the opposite direction to the existing joists. <<Randy,Why would he drop the ceiling when all he has to do is drill threw two joists?Joe Carola
To avoid drilling 3 inch holes in 2X10's.
Randy
>> To avoid drilling 3 inch holes in 2X10's. <<Why,there's nothing wrong with that. It's done every day where I'm from and been done in many many houses with no problems when drilled in the right spot.Joe Carola
Edited 2/24/2007 10:30 pm ET by Framer
That's a thought. We're already dropping it to go under the gas line in the ceiling, so we'd only need to go another 3/4". Thanks!
Well, the standard solution would be to call a plumber and have HIM notch the beams. Plumbers are experts at that.
(I say smash the round duct flat by 3/4".)