need ! plumbing vent hole in top plate…
have a 4″ /vent stack coming thru my sole plate (2×8 construction) on a outside wall…that’s the wrong place for any plumbing pipes imo, so I would like to bring it inside the envelope i’m thinking of letting it run up in the stud bay .(the pipe would be insulated from the back side with spray foam with the other side of the pipe running- just out side the vapor barrier/sheet rock),…… then bore a hole in the double top plate and turning it into the joist bay .??? I have 2×8 double top plates …2×8 studs on 2′ o,c’s 16″ bci’s and 1 1/8 t&g flooring
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Not clear to me...
... just what you're trying to do here. Can you draw @ post a quick cross-section from footing to roof to better illustrate your situation?
Taking a 4" stack - nominally 4-1/2" minimum OD for, say PVC - thru a 7-1/2" framed wall off-center can be done of course but doesn't leave much of a 2x8 on the thin side of the hole.
No way to re-route this up thru an interior chase somehow?
i drew this up...
mite be a bit hard to see (try ctrl + on your PC to make bigger)
Well...
... your sketch helps some but raises more questions than I had after rerading your original post.
I can only wish I were there to look this project over with you; I'm sure the two of us could put our heads together & come up with a practical solution. I agree about having a stack in an exterior wall isn't such a good idea; where is it coming from before it comes into your wall?
You refer to a sole plate but in your sketch the bottom-most portion of the vent looks to be oriented horizontally, like thru a rim or perimeter joist?
Maybe I'm missing something that the low-res image is leaving out of the picture?
This gonna have to meet local code at an inspection?
If it's strictly a stack vent & not expected to serve as a drain, perhaps for the vertical portion up into the joists above it could be reduced to 3" then increased again to 4" to pass thru the roof? That'd buy you some room in the wall cavity as well as allow for a smaller hole thru your top plate.
I am kind of curious -- we have a kitchen sink on the outside (north) wall of our house. The vent goes through the (2x4) wall to the attic. Never had a problem with it (in temps down to 35 below).
True Vents...
...generally aren't a problem in an exterior wall though they do take up space better left for insulation. They're not typically 4" diameter either, which is what piqued my interest. Something of that size is more commonly a soil stack, gets routed thru a plumbing chase or interior wall built deeper than normal to accommodate the dimensions of the parts used as well as keep things mostly in a straight line to reduce noise from 'stuff' that's headed down & out.
Where problems could crop up later on is if what's being called a vent actually serves a drain someplace up-pipe which then makes it a wet vent. Acceptable under certain circumstances but not usually routed thru an exterior wall.