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CuthbertRumbold · Sep 30, 2008, 05:02 PM

Hi plumbing experts,

I'm running a 1-1/2" PVC vent line vertically inside an interior (non-load-bearing) 2x4 wall, into an attic space and then up and out the roof. Problem is that the top plate of this wall lies directly under a joist. Any advice on how to best deal with this scenario?

Thanks!

Milo Dolezal · Sep 30, 2008, 05:27 PM

Cut the pipe 2' below the plate. Offset it with 2 - 45 degree bends. Continue to the roof.

CuthbertRumbold · Sep 30, 2008, 05:40 PM

Originally Posted by Milo Dolezal

Cut the pipe 2' below the plate. Offset it with 2 - 45 degree bends. Continue to the roof.

Thanks Milo... that will cause the 45 section to protrude outside of the finished wall and/or the ceiling - was hoping to avoid that (by notching something?)

Milo Dolezal · Sep 30, 2008, 05:43 PM

Well, let me see if we communicate:

When you are going straight up with your 1 1 /2" vent pipe and you run directly into a joist. Than: joist is 1 1/2" in width. To bypass this 1 1/2" joist that prevents you from continuing straight up , use 2-45's, drill hole through the plate and continue to the roof.... In other words, you will keep the pipe and the 2-45's within the 3 1/2" wall at all times. No protrusions to the ceiling or out of the wall...

Is that correct ?

CuthbertRumbold · Sep 30, 2008, 06:34 PM

Thanks Milo. OK, maybe we didn't communicate :)

Maybe if I draw this... I was thinking you meant something like this, which I had considered:

Maybe if I notch the top plate I can move the 45 section up? That's where I was headed when I decided to ask here :)

Milo Dolezal · Sep 30, 2008, 06:44 PM

Thank you... and kudos for the excellent visual ! Now I understand: the joist is running parallel with the wall and sits directly on top of the wall. (... bad framers, bad framers.. :-D )

You said it: you can notch the joist so you can get into the ceiling. If you have to go straight up in that same area - and you have 2nd floor sitting on top of that joist - than you will have to notch the same joist on top to get back into the upper wall.

You are using 1 1/2" pipes so notches will be small. Also , that joist has plenty of support being positioned directly, and lengthwise, on top of the double plate. I would not worry about structural issues at all...

Once you get into the ceiling, you could also use 90 ell , run your vent to the other nearest wall that doesn't have a joist on top of it - and up to the attic.

Of course, if there is an attic right on top of this joist, than go straigth up w/o notching top or the joist.

Hope that will help...

CuthbertRumbold · Sep 30, 2008, 06:52 PM

Originally Posted by Milo Dolezal

Now I understand: the joist is running parallel with the wall and sits directly on top of the wall. ( .... bad framers, bad framers...! :-D )

Exactly! I confess, I am the bad framer :) but the wall had to be exactly there for reasons I won't bore you with!

Originally Posted by Milo Dolezal

Of course, if there is an attic right on top of this joist, than go straigth up w/o notching top or the joist.

Yes, attic above, can go straight from there. Thanks so much for your help!

Milo Dolezal · Sep 30, 2008, 06:57 PM

One more thing: We drill, we don't notch. Go to HD and buy drill bit for 2" ABS pipe ( made specifically for drilling for 2" ABS pipes by Milwaukee - sorry, I cannot recall the exact size, but I think is something like 2 9/16". Also you will need 1/2" chuck drill or angle drill ).

I am suggesting 2 9/16" drill bit because the hole will take not only the 1 1/2" pipe but also the hub of your fitting. Drill through double plate and continue drilling about 3" into the joist from the bottom. Wear goggles ! It is lot of pushing - but once you get it done, you will appreciate the final effect. You will end up with a nice, clean hole to insert your entire 45 fitting, including the hubs.

Let us know how you did..

Glad I was able to help...

But 1/2 of the credit goes to you for the excellent visual! :D

CuthbertRumbold · Oct 1, 2008, 06:02 PM

Hi Milo,

It went well!

The joist was not exactly centered over the top plate like I drew it, so that helped - the hole breaks out the side of the joist very nicely on one side and not at all on the other. - that's good! (I nailed a 2x4 temporarily over the side of the joist so it wouldn't break out while I was drilling).

I ended up going right from the one street 45 into a 90 deg ell and then over about 16 inches before going up through the attic floor. This wasn't strictly necessary, but it lines it up with a wall in the attic above that I can use to anchor the rest of the vertical run.

Here are some pics:

Close up:

From below:

Thanks a lot for your advice, it helped a lot. I probably would have hacked it to pieces with the sawzall - this is much better.

PS: You mentioned wearing eye protection while drilling which is a good idea. I'd add that wearing good heavy gloves is also a good idea! If that hole saw binds up while drilling it can be murder on your knuckles!

Cheers,
Roy

Milo Dolezal · Oct 1, 2008, 06:06 PM

Thanks for the follow up. It is a nice and clean job. We like it that way. I can even see a bit of slope in that horizontal section of the vent pipe. Well done !