# 2" PVC in 2x4 Exterior Wall?



## stubits (Dec 30, 2008)

Is it possible to run 2" PVC through a 2x4 exterior load bearing wall? Specifically, can it be run through the top and bottom plates, if not the vertical studs? If not, are there any mechanical reinforcements that can be used to allow it?

Thanks!


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## Bob Mariani (Dec 1, 2008)

you can strap the plates with steel, but it is an extremely bad plan to run pluming (no room for insulation) in an exterior wall.


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## stubits (Dec 30, 2008)

I know it is less than optimal, fortunately it is only 1 vent pipe and nothing else. The this is an addition onto a brick rowhouse, so the 2 interior walls are brick. 

So, code-wise I can get away with a 2" pvc running vertically through a 2x4 wall, as long as I use straps on the top and bottom plates?

That is great news. Thanks!


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## Bob Mariani (Dec 1, 2008)

it's moves like this that we should not allow DIY work done on a house unless everything is documented so someone else buying the house knows it has been hacked to death and no longer works properly. 

DO NOT DO THIS!


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## stubits (Dec 30, 2008)

Is it against code? That was my initial question and your answer seemed to indicate it was possible.

Are plumbing vents not allowed to be run in exterior walls? 

Again, in my current situation there are no interior walls available to run the vent through. With a little more effort I can run it through a 2x6 exterior wall, but it seems like in your opinion that's no better. 

I really, really resent the insinuation that I am hacking my house to death. I have posted question after question in these forums to ensure that I am doing things correctly. I've hired an architect to design the addition and a structural engineer sign off on them. I am doing the work myself because I enjoy it and specifically because I don't want my housed "hacked to death." I appreciate the help you offer here Bob, but honestly, you made a huge and inappropriate leap with this one. And for what it is worth, there are plenty of licensed, bonded and insured remodeling contractors out there that do crappier work than the average homeowner, should we document all work done by anyone, anywhere?


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## tpolk (Nov 7, 2009)

my biggest concern would be how little plate is left if this wall carries the roof and not another floor, you have potential for a hinge /stress point there. is a floor on this or a roof


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## stubits (Dec 30, 2008)

There is a floor above this and then a roof above that, but the floor joists and the roof joists do not bear on this wall. This wall basically only carries its own weight.


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## Bob Mariani (Dec 1, 2008)

it would help. Especially since building inspectors rarely do their jobs and home inspectors that you hire when you buy a home do even less. I have done over $400,000 in work this year on repairs to unsuspecting homeowners that had inspections and still get screwed.

Issues: 
how are you going to protect this plastic pipe from someone driving a nail from the outside while installing new siding? 
How are you going to get the code requirement of R-13 insulation value? (now you have a code violation)
What did you plan to use to air seal these penetrations?
Are you using the code required fire barrier caulking at the plate penetrations?
When you go thru the roof it must be 3"... Is this planned?
What strap material do you know to use for the required steel thickness? 
What length is needed for this strap?


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## stubits (Dec 30, 2008)

Bob- I get it, really I do, my house was flipped before we moved in and we've had nothing but problems since... a bit part of the reason I do work myself now; I don't trust others so much. So, I get the dangers that can come from bad work. That is why I am here... and that's why I am here before I start the work, rather than after the drywall is up and painted, like so many others.

So, it seems like running the vent over to the 2x6 wall could actually help a little bit, no? At least with some of the issues you've raised below.


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## tpolk (Nov 7, 2009)

pretty sure these are some of his questions


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## Bob Mariani (Dec 1, 2008)

yes that will help. A vent only you will get away with. As mentioned verify all the other issues I mentioned also. Use spray foam around the vent pipe to avoid condensation buildup. Cold air is moving thru this pipe. In you 2X4 wall with most likely improper air sealing in the house you will get too much condensation on this cold cramped pipe.

Glad to hear you will take the time to do it right.


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## stubits (Dec 30, 2008)

Thanks TPolk, you're right... and thanks Bob, I really appreciate your experience. I wouldn't be doing any of this correctly were it not like folks like you. 

So, I can use batt insulation (roxul) in the wall, as long as I spary around the penetrations?

Is any strapping necessary if I run through the 2x6 wall?


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## Bob Mariani (Dec 1, 2008)

yes it still must be strapped.

Roxul will not get you enough insulation around the pipe.

Spray foam is for the pipe. Fire barrier caulk is required for all penetrations between floors.


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## stubits (Dec 30, 2008)

Ok, I am spray foaming some of the walls, but was planning on doing roxul in the 2x6. Can I do spray foam around the pipe and then roxul in the rest of the stud cavity? Or just spray foam the whole cavity?


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## Bob Mariani (Dec 1, 2008)

your method will work fine.


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## Jim F (Mar 4, 2010)

Following this exchange, I must add my two cents. With the purchase of my 1939 two story with a 1990 one-story addition, I got the best of both worlds. The original has many homeowner added modifications. There is a joist hacked into to make room for the upstairs tub trap. I found copper drain pipes fitted inside of larger diameter PVC pipes surrounded by plumber's putty then wrapped around by elecrtical tape. After dealing with a slow moving kitchen drain for years, I removed an access soffit in the basement and took one of these apart to try to snake out the drain pipe. About 6 ft of unraveled electrical tape came out with hair and other gunk resolving the slow drain issue. This was replace by a 99 cent rubber boot with hose clamp adapter.

I'm now in the process of tearing things up in contractor-built 1990 addition and renovating the bathroom, hallway and laundry alcove. The shower drain failed due to movement in the shower floor which could have been prevented by a thin-set morter bed. There was a rigid dryer vent that spanned the entire 14 ft width (Dryer on one side, vent on the opposite side. This vent pipe was installed in the air space between the subfloor and the 4 inches of rigid foam insulation. The vent leaked steam over a period of 10 years, destroyed 3 joists and the subfloor. When I took this pipe out it was put together with sheet metal screws, a no no, and no duct tape. I don't know how they thought the homeowner was supposed to get to these pipes to clean them out. To add to that, one section was crushed down to accommodate the water supply pipes. Tearing out the drywalls I found 24 IOC 2x6 studs. The roof is 24 IOC 2x4 rafters. I don't know what the code is for this but having walked on that roof, Ican say there is plenty of bounce. The ice took the gutters down on the addition within 5 years. Just doubling up the hangers improved that situation. All in all, I have been dealing with the shortcuts these contractors took for the last 15 years I have owned this property. 

I have encountered many knowlegable and helpful contractors on this site When I find a good one in the real world, their number stays in my contact list. My plumber is one I kept, the roofer is one I let go. He did a good job on the roof as far as I could tell but I could not get him back to fix a minor problem he created when he took the gutter loose to install the roof. He claimed his method did not upset the level of the gutter. I say it functioned well before he moved it. It's too bad because that't all that prevented him from getting good references from me. I have also learned to begin my search on bbb.org . It seems like there are too many bad apples that just want to get the job done fast, collect the money and move on.


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## larrypark (May 28, 2012)

*Bob Mariani: Comment Re Home Inspectors*

I realize the comments on this forum are almost 4 years old, but having just come across it, I hope by now the chap looking for an answer to his question "can I run a 2" PVC vent in an exterior wall" has finally gotten the advice that even my dear friend Bob seemed to have overlooked:

Hire a licensed plumber!

In many cases an air admittance valve can augment an atmospheric vent.

But a 2" vent in an exterior wall, even if the studs are 2x4s, is possible. Several ICC IRC codes come into play: e.g., drilling, notching, boring of studs, top and sill plates as well as the required protection of the plumbing where they pass through the sill and top plate. A licensed plumber can easily address all of those code concerns.

And, Bob, as a "useless" home inspector here in Atlanta, I just don't know how in the world we've been able to build houses here without your expert guidance and oversight. Connecticut is so doggone lucky to have you. I can only hope they never let you leave!!


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## plummen (Jan 10, 2010)

Yes sometimes dwv piping has to be run through exterior walls,and yes they do make braces/brackets to help support the walls for this purpose.
You can always run the vent across the ceiling/rafters to another point where it can be taken through the roof by itself or another existing vent.
A picture of your situation would make it much easier to give suggestions


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