Single Wet wall (Back to back bathrooms)

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Jb9

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Hello,

I am trying to simplify all the plumbing in a 2 story house I am designing. I want to have a single interior wet wall that will house the plumbing for 2 full bathrooms (back to back) on the 2nd floor and a 1/2 bath on the 1st floor opposite a washer hookup. Does this seem reasonable? How deep/wide should my wall be to make this easiest? I am trying to find some sample diagrams online for a single wet wall with this implemented but I can't find anything.

Here's the layout I want:

Full Bathroom | Wall | Full Bathroom
| |
Half Bathroom | Wall | Washer

I am hoping to frame the wall perpendicular to the floor joists.

Thanks
 

Jadnashua

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If it's not a load bearing wall, and you want to run the drain lines through there as well, that means at least a 3" pipe, a 2x6 in non-load bearing should work, otherwise, if it is load bearing, you may want it deeper. One that deep would allow use of a 4" drain line, which may be required depending on the fixture units. I'm not fully up on all of this, so wait for confirmation.
 

Reach4

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I would consider adding a laundry chute.
You may want to bury an extra conduit to the attic in case you later want to add ceiling fans or whatever.

I don't know the standards, but 5.5 inches seems sufficient. Do insulate the wood that is against the outside wall.
 

Dj2

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For your purposes as described, double 2x4 will be better. The additional inch and a half will allow you a 4" pipe and some.
 

Reach4

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For your purposes as described, double 2x4 will be better. The additional inch and a half will allow you a 4" pipe and some.
Interesting. How about staggering the 2x4s to allow horizontal pex and wires to weave around rather than having to cut through lumber? I guess that would have downsides also.
 

Dj2

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Reach4,

You mean leave a gap between the 2x4s? I guess you can do it for a non bearing wall, I have never seen it like this.

I'd just have the 2x4s side by side and drill through the studs as necessary. But the main advantage is the width. In most cases the additional 1-1/2" will not create problems, so why not?

BTW, this arrangement will allow two in the wall medicine cabinets back to back.
 

Jb9

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Thanks for the suggestions. I do plan on running the soil stack in this wall. If I framed a wall using the double 2x4 method, that would essentially mean there is 7" of space in the cavity, right? Wouldn't that also mean that a hole for the soil stack through the sill (bottom) would be through a cutaway section of each 2x4? If I went with the 2x6, the hole would be through a single piece of lumber. I was looking at the discussion and forgot that dimensional lumber drops a half inch.

How about a wall with double 2x4 studs and a 2x8 sill and plate?
 
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Dj2

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Double 2x4s will be 7" wide.
A 2x6 is 5-1/2" wide.
You get an extra inch and a half.
Yes, that means that you have to notch both 2x4s.
2x8 sill won't work because it will be 7-1/2" wide, UNLESS you rip 1/2" off. If you can rip it, you can use it.
 

Jadnashua

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For sound transmission, there are distinct advantages of having offset studs. The means that once you install the wall board on each side, sounds are not transmitted directly through the wood to the other side's wallboard, causing it to act like a passive sound radiator. So, you could use a 2x6 or 2x8 and use your studs such that they are flush with the outside on the room they are serving, and space them so that they are essentially at 8" OC to the opposite wall, but still 16" OC on the side in question. This is often done in firewall situations or common walls of multi-family dwellings, and then, if they use insulation there, it also improves things since it can be wound back and forth horizontally and still have some effect rather than having a solid wood structure connecting both sides for heat transfer (or sound, so it helps in both ways).
 
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