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drcheap 01-09-2011 12:33 AM

Insight on framing inset and rerouting vent pipe
I am in the process of remodelling a bathroom, the plan is to install a new valve and tub/shower fixtures, a new inset box along the long wall, use cement board, and cover it all up with some very nice tile with a few design touches.

So I've pulled out the old tile, greenboard, and sheetrock surrounding the tub area. Next up was to frame in the inset box, but I've found my first hidden treasure -- the vent pipe! Turns out this thing comes up through the slab (first floor bathroom) and goes up between the studs, right through the area I want to put the inset box.

I don't want to change the design, so it looks like my only other option is to reroute the pipe out of the way. I know about the rule which says that a section of the vent can only be horizontal if it is at least 6" above the flood level of the fixture it vents for. Well this is not a problem as I am putting my inset box about 13" above the lip of the tub, leaving enough room for the pipe to come up well above the 6" before the 90 degree turn.

Now it's a 1-1/2" pipe (almost 2" OD) so drilling a hole in the neighboring stud would leave pretty much nothing. This is where I have some doubts, and could use some enlightenment from those who have dealt with something like this before...

Should I cut out part of the stud & brace the remaining parts to the adjacent one (on the right) with 2 new horizontal blocks? And what about placing a new vertical section between those two horizontal ones? This is an interior wall close to the center of the house with a closet on one side and the bathroom on the other. I don't think it's bearing much load, so maybe I should I just remove the stud alltogether and stop worrying about it so much. I do need something to attach my cement board to though!

The other reason I am a bit leary about eliminating that stud is that I'm already having to cut the one to the left of the pipe as that one is close to the center of my box. Now the box itself will "connect" that stud back together, but it's not supportive like the original piece.

To help make sense of all this, I've whipped up some drawings. They aren't exactly to scale, but they are close enough. Here is the original state of things:

And here is what I'm thinking of doing (with a few optional items, see below):

I'm not sure if it is necessary to provide the supports marked A, I figure this would help with the stability of the box though.

The squiggle marked B is a support strap for the vent pipe, but I'm not really sure if this is necessary either. It's not exactly "solid mounted" as it is, so I figured it might be good to support the added weight and odd pull of the offset portion.

The stud marked C is the additional part I referred to way earlier, not sure if it would be of any help. If anything, it provides more places to anchor the cement board.

And by the magic of the interwebs....let there be replies! :thumbup:

Ron6519 01-11-2011 11:19 AM

I'd just drill the stud.

AndyGump 01-11-2011 01:17 PM

1 Attachment(s)
Something like this is were you might want to do.

This is done all the time and this is what I did for situations like yours when I was a General Contractor.


drcheap 01-11-2011 09:06 PM

So a 2" hole, er make that two of them, in a standard 2x4 stud is okay? I did a little more searching on that idea and I do see that some sources state that if the stud is doubled up the max bore is increased from 40% to 60% which just barely clears that 2" need.

That is a nice drawing AndyGump, and I see how you doubled up the stud at the bottom for the larger hole, but what about for the top one?

And here's the next complication for this...the design calls for a fairly large inset box (about 26" inside width after finishing with tile. So after going in and making some more measurements on the actual wall, I've realized that I am not even going to able to simply double up the stud next to the pipe -- the framing for the box will extend a bit beyond the existing stud and into the space that the added stud would need to occupy.

I've revised my drawing of this to show it a bit more clearly:

So what I'm thiking now that I could double the stud, put the holes in it, but then go ahead and cut it where it meets up with the box. This keeps the vertical support for the box, eliminating those silly angled pieces. Something like this:

Or, while I'm having fun with my new 2" hole saw, I could make two more holes (in horizontal boards) if I extend the box top/bottom pieces all the way to the next stud at the right. I think this would give the whole thing more stability over the prior one:

AndyGump 01-11-2011 09:24 PM


I could make two more holes (in horizontal boards)
Don't do that, just the holes in the studs would be fine.

It is because of things like this that I always spec. out a 2 x 6 plumbing wall when possible.


drcheap 01-11-2011 09:38 PM


Originally Posted by AndyGump (Post 568196)
It is because of things like this that I always spec. out a 2 x 6 plumbing wall when possible.

Yeah, unfortunately I bought a 10 year old house full of baseline home builder grade stuff (read: financial shortcuts), so the constraints are plentiful when it comes to my projects here :mellow:. Nothing near as bad as the 40+ year old condo though, yikes!

The good thing is I'm making notes of all this sort of stuff as I go along, so in the future when I help design and build my own house, I'll be able to avoid a lot of extra headaches (there will be enough as it is I'm sure).

drcheap 01-13-2011 01:12 AM

5th time's a charm!
Okay, so revision 5 of my plan is almost complete. I went with the plan of doubling up the stud and boring a 2" hole for the pipe at the upper and lower locations. The hole itself will support the weight of the pipe -- which needs it because it isn't connected to anything above the top plate apparently as it moves freely up and down a few inches after cutting it :001_unsure:.

Now due to how close it is to the original stud (about 1-2"), my elbows actually end "inside" that stud, so to get that extra bit of space I need I've decided to cut the old stud a little above and below where the horizontal pipes will be. Then I've put in two additional layers of veritcal attached to those original pieces. As usual, pictures are better at explaining:

Since the drilled holes, and thus the pipe, only pass through 2 actual studs, I am pretty sure that still meets the requirement of "when studs are doubled, drilled holes should not exceed 60 percent of the stud depth" without violating the "holes of maximum diameter should not occur in more than two consecutive studs" part :thumbsup:.

All that is left now is to cut and meld the new plumbing bits into place and I can move on to the next phase of the project.

drcheap 01-13-2011 03:15 AM

So enough with all these silly diagrams, here's a photo of the outcome:

And it definitely didn't need those extra horizontal supports on the far is quite solid now, enough that I can yank on it all over and even stand on the box "bottom" without any significant flex :cool:.

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